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A D D A"Klss"
OF GOLOR
TOYOURBLAGK ElWHITE
WEATHERGHANNEL
COMMUFJITY
CERRO ALSO MAKES A FULL LINE OF OTHER PASSIVES.CALL COLLECT FOR PRICES & OELIVERY
MPB|)TtrGTS
I
ALSO AVAILABLE IN U.S.A. FROM ANIXTER PRUZANOIVISION OF CERRO CORPORATION
RMS CL.LhOO, A MAJOR C()NTRIBUT()R!That's r ight the CA-2200 t i l t attenuator makes aFCC standards.
1. Here 's how:FCC s tandards requ i re a ba lanced s igna l to yoursubscr ibers TV se t . The CA-22OO, ava i lab le in
5 db or 10 db va lues , compensates fo r h ighf requency a t tenuat ion on long coax ia l cab lenouse orops .
2 . The un i t p rov ides reverse t i l t f rom 5 lv lHz to300 MHz. l t a lso he lps prevent c ross modu la t ionprob lems when used w i th top o f the se t conver te rs .
mator contr ibution in helping you comply with
3. As we i l , i t ' s idea l fo r p rov id ing a ba lanced s igna lto the f i rs t ampl i f ie r inpu t when sweep tes t ingyour cab le sys tem, by compensat ing fo r t runk- l inecoax ia l cab le a t ten tua t ion .
RMScArv DrrlrsroN
50 Antin Place, 3ronx, N.Y. 10462. Call Collect (212) 892-1000. Canadian Representatives: Deskin Sales qorp.
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i u N E , 1 9 7 5
f MANUFACTURING COMPANY
wAco. TEXAS 767'tO
CATJ for
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OFFICERS/DIRECToRS
Kyle D. Moore, Prcsident
Bcn Campbel l , V.P.
C.I l . ( l tunk) Dodson, Scc/ ' l 'sr
Wi l l iam Risden, Director
Warren l . ' r ib ley, I ) i rector
Robert B. Cooper, Jr . , Bxec. Dir .
Richard L. Brown, ( len. Counsel
S'I'AI.'F
R.B. Cooper, Jr . , Edi tor in Chie fCeleste Rulc, Managing I ld i torJanet Carpenter, I ld i tor ia l Asst .Debbic Teel , Product ion Asst .S.K. Richey, Contr ibut ing Fid i tor
OF-FICES
42O9 NW 23rd, Sui te 106Oklahoma Ci ty, Oklahom t 7 3 lO7Tclephone (4O 5) 9 47 -47 7 7
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l ' h c ( i ) m m u n i r y A n t c n n a ' l e l c v i s i o n A s s o c i -a t i ( ) n , I n c . i s a n o n p r o f i t c o r p o r a t i o n u n i l c rC h a p l c r 1 9 , I i t l e t 8 o f L h c S t r t u r e s o f r h e
S t a t e o f O k l a h ( ) n l r . N o p r r t ( ) f t h c ( l o r p o r r r c
xssc ts ( ) r tDcon lc shr l l t )c thc p ropcr tv o f i t s
mc iJ rbcrs i such assets and ; r rconre sha l l l>c r le ,v o t e d c x c l u s i v c l y t r t h c p u r p o s c s o f t h eC o r p o r r t i o n -
C o p y r i g h r A f ) 7 5 b y t h c C o m m u n i r y A n -t e n n a I c l e v i s i ( ) n A s s o c i e r i o n , I n c . A l l r i g h t srcscrver l . Pcrmiss ion to rcpr in t anv matc r ia lo r por t ( )n thcreo f musr i )e g ivc i l t ) r ' CA l ) \ ,I n c . p r i o r t o r e - p u l ) l i L a t i o n .
A T JJUN.1975VOLUME 2N U M B E R 6
PUBLISHED MONTHLY, AS ITS OFFICIAL JOURNAL, BY THE COMMUNITYANTENNA TELEVISION ASSOCIATION, INC., OKLAHOMA CITY, OKLA-HOMA AS A SERVICE TO THE CATV/MATV INDUSTRIES SERVING THEAMERICAN TELEVISION VIEWING PUBLIC.
_CONTENTS_Modulated or CW Garriers?
C A L I B R A T I N G S L M ' S F O R A C C U R A T E _Mid Sta te Communica t ions has a new box tha ta l lows you to compare meter ca l ib ra t ion w i thboth modu la ted and un-modu la ted car r ie rs . . . . . . . . . . . g
Commie Weather ChannelCOLOR-ADDER MAKES lT RED - S teveRichey does i t aga in w i th a s imp le , one lC c i r -cu i t tha t tu rns your b lack and wh i te weather o rmessage channe l in to red , b lack , and wh i te . . . . . . . . . . 16Dipoles Are For The BirdsANTENNA BASICS - Par t One o f a summer-long ser ies on in tens ive CATV antenna theoryb e g i n s w i t h t h e b a s i c d i p o l e a n t e n n a . . . . . . . . . . . . . . . . . . . . 1 gHello Test
SADELCO 260-4 ANALYST - CATJ bemoanslack o f indus t ry acceptance fo r a mu l t i -purposetest set that we bel ieve deserves more universaluse by sys tems o f a l l s i2es . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2gSave Embarrassment
COMPUTER AIDS RATE INCREASES - Oneway to he lp bu i ld your case fo r a much deservedrate increase is to have al l of the facts at yourd isposa l . A South Caro l ina sys tem opera tor te l l sy o u h o w . . . . . . . . . . . . . . . . . . . . . . 3 8
CATA- tor ia l (Ky le D. Moore , CATA pres ident ) . . . . . .4
T E C H N I C A L T O P I C S ( C o r r e s p o n d e n c e ) . . . . . . . . . . . . . . 4 4CATA ASSOCIATE'S ROSTER (Suppt ie rs whos u p p o r t y o u ! ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 6ASSOCIATE'S SHOWCASE (New Products,s e r v i c e s ) . . . . . . . . . . . . . . . . . . . . . . . 4 6
No, L inda Lovelace is not loose in CATV land. But acouple of weird looking weather channels uround th"country now have red l ips p lanted on their weather in_strumentsdisplayed in red wi th a b lack and whi te cam_era! Find out how on Page 16. Weather channel byRobinson Engineer ing; l ips by Debbie.
3J U N E , 1 9 7 5
.T() R IAL KYLE D. MOOF|E, President of CATA,
WHAT'S IN A NAME?
Names. They used to be self explanatory.Take Standard Oi l Company as an example ;Standard Oil obviously was not in the homebu i ld ing bus iness . But EXXON. . .good gr ie f ,that could be almost anything. They couldgrow avocados or sel l penci ls on the streetcorner .
Or take the National Community TelevisionAssoc ia t ion . Par t fo r par t i t obv ious ly meanta na t ionwidc (Nat iona l ) Ioca l l y o r ien ted(Communi ty ) p ic tu res and sound (Te lev i -s ion) g roup o f en t repreneurs (Assoc ia t ion) .NCTA startcd off as the national CommunityTe lev is ion Counse l , in Pennsy lvan ia , bu tchanged Counsel to Associat ion in the processof becoming a legal enti ty. Of course that hasnot been the on ly change in the name; in the60 's the word Communi ty became a newword ; Cab le . Most who were around 10 yearsago, whcn the change took p lace , reca l l tha tsomc proponents of change at the t imewanted a more dras t ic changc in the name;severa l even wanted to e l im ina te the wordTelevision. A popular (or i f not popular, atlcast often bantered about) proposal had theNCTA becoming the NCCA; wh ich was tostand for National Cable Communications As-soc ia t ion . That one missed by a few vo tes a tthe t ime; bu t i t s day may ye t come.
Now let 's take CATA or Community Anten-na Television Associat ion. Community obvi-ous ly re la tes to the loca l i zed (o r cen t ra l i zed)area of operations. Antenna probably needsno exp lanat ion . Te lcv is ion cou ld bc a par t o fthe two-word phrase "an tenna ( - ) te lev i -s ion" o r i t cou ld s tand a lone; mean ing s imp ly"s igh t and sound communica t ions" . Aga in ,Assoc ia t ion necds no add i t iona l exp lanat ion ;i t is a voluntary col lect ion of people with simi-la r bus iness goa ls and ac t iv i t ies .
At CATA I am often asked ,,why did CATArevive the word community after NCTA haddropped i t many years p r io r , '? I am fu r therasked: Does "Communi ty Antenna" meanthat CATA represents only independent oper-a to rs ( tha t one leads to ,what i s an indepen-dent opera tor? ' )? Does , ,Communi ty Anten-na" mean tha t CATA represents on ly smal lopera tors (wh ich Ieads to 'what i s smal l? ' )?Does CATA represent only systems which donot o r ig ina te p rogramming (wh ich leads toca tegor iz ing o f p rograms)? Does CATA rep-resent only systems which do not originatepay movies or sports (which leads to the tele-vising of local high school sport ing events)?
4
Or, does CATA represent only systems whichnever intend to provide broadband services(wh ich once aga in leads to sys tems tha t mixin services normally associated with broad-band with their present off-the-air signals ont h e s t a n d a r d 1 2 V H F c h a n n e l s ) ?
CATA's fu l l name was chosen w i th the de-l iberatc intention of bringing not only theword but also thc concept of , ,community"back in to CATV. That may need some fu r therexp lanat ion . The NCTA, and the FCC, in anattempt to sel l their l ine that CATV has sreatp o t c n l i a l b c y o n d t h c " m c r c r e - t r a n s m i s s i o n "o f b roadband tc lev is ion s igna ls , has op ted fo rthe c l im ina t ion o f the word "Communi tv "and i t s d i rec t rcp laccment w i th the word"Cab lc" . And in th is word-game, many haveperhaps forgotten that the roots of CATV arein thc communi ty i t se l f .
CATV's operation is, in virtual ly everycasc, created at the local level. The local ter-rain, the local topography, the local distr ibu-t ion of people and homes along creek or r iverbeds or strung throughout val leys creates theneed. The need, for example, for school teach-er , Iohn L. Maxwell of Benton, Ohio to designand bui ld his Wired TV System in 1953 waslocal ly mandated. Nobody from Washington,or even Columbus conceived the need forBenton's Wired TV System. Local people inBenton did; and John Maxwell f i l led thatneed.
In virtual ly every casc, the services CATVprovides and rates charged for these servicesre f lec t communi ty s tandards , communi ty as-pirat ions and community economics. In thclong run, and in the day to day operations, i t isthe community in which the system operatesthat determines system need and system suc-cess. And i t is to this community that the sys-tem owes both al legiance and responsibi l i ty.
CATA was founded upon these recoqni-t ions ; and i t be l ieves s t rong ly tha t serv icesdelivered, rates charged, and provisions ofcontractural agreements between system op-erators and the communit ies served are pri-mari ly ( i f not total ly) matters of local con-cern; which must be individual ly tai lored tothe individual and unique requirements ofeach community. Such matters cannot be na-t ional ized or mandated from Washington, byany real ist ic stretch of the imagination.
And so too i t is and must be with any and aII"services" offered or carr ied by a communi-ty system. Broadband services, pay cablemovies, pay cable sports, access channels
CATJ for
and the l ike may well be desirable and evennecessary in many communit ies. Or none ofthese expanded services, or only some ofthese expanded services, may be appropriatein a neighboring community.
The needs of the community, determined onan individual basis by each and every com-munity, must be ref lected on a community bycommunity basis. The "big brother in Wash-ington knows best" approach always has asits objective "equalization of servicesthrough national izat ion of pol icies, rules, reg-ulat ions and even Iaws". However, the feder-aI government has recently determined thatthey cannot tel l ci t ies and states how to spendevery federal tax dol lar that si f ts back downto the local level; and slow progress is beingmade to return to the cit ies and states thealmost lost right of self determination.
And while CATA recognizes that certainfederal guidel ines may be appropriate andmay even be educational to the city or towngroping with the regulatory position it shouldtake with respect to i ts local CATV system,CATA also bel ieves that the federal govern-ment has no business or r ight or just i f icat ionto become involved in matters of purely localconcern which Washington has demonstratedtime and t ime again i t is not equipped tohandle with the same speed, or aptness aslocal people.
The community is the foundation of our en.deavors. As no two communit ies are al ike, sotoo are no two community antenna televisionsystems al ike. With each variat ion betweenCommunit ies there too must be variat ion be-tween each community's CATV system. Na-t ional izat ion of al l or most al l rules and regul-at ions concerning CATV can lead only to theult imate fai lure of CATV to be responsive tothe needs of the singular community which i thas been designed to serve. And when ourindustry is regulated out of being responsiveto the needs of our individual communit ies, infavor of being responsive only ult imately tosome Washington perceived national com-munications pol icy, we are as an industry aIIwashed up. And with our demise wiII go ourcommunity's only real hope and aspirat ionsto ut i l ize for the good of thecommunityourbroadly conceived potentials for communitygood and betterment.
If you believe that the decisions affectingyour system or systems, your town or towns,what your systems offer and what theycharge, are mainly of concern to you and yourcommunity, f i rst and foremost, then you un-derstand why CATA is called the CommunityAntenna Television Associat ion.
J U N E , 1 9 7 5
Glen ShaferGeneral Manager,1 3-years Manager\ bstern RegionalTechnical Operationsfor Jerrold
Joe E. HalePresident,
16-years inCATV engineer-
ing, veteranSystem Operator
Cable Dynamics Incorporated now offersrapid, high quality, low cost Repair Servicesfor :
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conhols 1of lo-ster set up, put lhe electfonics, ; iA - t in io rock conl jqurot ion lor heo. l enC
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s e e r n g t h o l y o u o r e , ( o n d y o u c d n t s e es p e n d i n s o b u n d l e o l d o u q h ) w e ' v e s o ly o u r n u m b e r s 1 8 5 0 o n r l l 8 6 0 S e n d { o rcomple te specr l i co l ion : r o f ca l l r . co l lec l
1 o d i s c u : r ; y o u r p d r l r c ! 1 o : p l o n l r n d r n1- .nsnce prob lems
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Y o , o n r . . W o v - l ^ k : , 8 5 0 . w e - p - r
o n d i 8 6 0 r e c e i v e r t o c h e c k o u t o n d m o r nlo rn cn opefo t ing CATV sys tem ond ihes u b s c r i b e r s w r l l p r o b a b l y n e v - . r s e e ot h n s B e c o u s e t h e 1 8 5 0 h o : t h e , ; o m e
i n c r e d i b l y i o s l ( l m s ) s w e e p p u l : e l h o t o u r
fj j J : : ;:";"""; :[?; l;:: i ; ]1,::: ; " ". \nAVe TE ]<has o tune, l RF c , .cu i t {o f t r iooe i lno oIND]ANA INCORPORATEDP O Box i90, 66 l lo: th Fr i t Avcnu.,B e e c h G r o v , - , I n d i o n c 4 6 1 0 7P h o n o ( 3 1 ? l 7 8 3 3 2 2 1 T V r ' X 8 1 0 3 4 1 3 2 2 6
6 CATJ for
'l[mr I ca,n harc a rcd-hot shrrwithout burninga hole in nryburlptS'
"Managing a CATV stationis a little like having threeheads. I'm the boss, the newsdepartment and the com-mercial production office allrolled into one. But even athree-headed man gets onlyone paycheck, and we haveto cut expenses wherever wecan.
"The one thing we don'thave to hassle with is thisKodak Supermatic 200 soundcamera. At less than $426,it's relatively inexpensive.And, let me tell you it's onesmart investment.
"I t not only shoots l ip-synch super 8 sound movies,but the built-in recordergives me on-the-scene voice-over capabilities. You canalso postdub a voice-over,music, or other effects on arecording projector. There'sa 200-foot magazine forcontinuous shooting and a5O-foot magazine for shorterstories.
"There are no lishts orcables. But I do keei an extrafilm cartridge and batteriesin the glove compartment in
"Whether you're on your way to a three-alarm blm or a three-legged race,the KodakSupermatic 200 sound camera can br ing i t home on economical suoer 8."
case the news of the centurybreaks on my way to work.
"Ifyou want to knowmore than I've told you, just
clip out this coupon. As forme, l've got a story to put onthe air."P r c e i s s ! b l e c t l o c h a n g e w t h o u t f o t c e
Company
City
llodak Sunermatic200sound Gamera.Eastman Kodak CompanyDepartment 640Rochester. New York 14650
fl Please rend me more infor-KEEEE mation on the KodaklJ Supermatic 200 sound camera.
Name
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J U N E , 1 9 7 5
CANTITEVER MOUNTS?So whot 's new !
e've been doing it for yeors !
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CATJ for
A New Approach
MIf)-STATECOMMUNICATIONS vs.
SLM/FSM CALIBRATION
Open Mouth*Insert Meter
During the months of October-Janu-ary just pasL, CATJ ran a four-partseries dedicated to exploring the pres-ent "state of the art" of field-strengthor s.ignal-level meters. In that serieswe investigated the various approach-es taken by manufacturers in develop-ing for industry use meters which ac-curately (or not so accurately) read outfor the operator the apparent or realRF (carrier) signal levels present.
The problems associated with accur-ately reading signal levels in the fieldunder often times adverse conditionsare many. Most were covered in abun-dant detail in the four-part CATJseries just referenced and will not bebelabored here again. Will not, that is,save one: the problem associated withmeters which employ a peak-type de-tector circuit to sum the apparent totalsignal power present from both thecarrier wave and the associated modu-lat ion.
As CATJ noted on Pase 29 for Jan-uary, "11 seems to us that one u)aA losettle the industry squabble aboutwhether Aou aUgn an SLM/FSM on anunmodulnted (CW) carrier or trg toutikze a modulnted TV signal is formanufacturers of reference signal gen-erators to prou'td.e sonxe simulnted uid-eo modulntion capability for the refer-ence signal generator."
The basic question? On a typical me-ter, what is the difference in indicated
J U N E , 1 9 7 5
level reading between a peak-readingdetector meter that is aligned on a CW(i.e. non-modulated) carrien and thatsame meter in use in the field readingnot CW carriers but amplitude modu-kt,ted uid,eo catriers? Is the difference0.5 db , 1 .0 db , 1 .5 db , 2 .0 db?
Is the di f ference the same ( i .e. is theratio between CW carrier readings andmodulated carrier readings'identi,cal)for eueru portion of the rmeter scal.e?To put it another way, if on a particu-lar meter you find upon testing analy-sis that the meter reads with a refer-ence carrier generator source + 10dBmV for a CW carrier and *9 dBmVfor a modulated (AM) video carrier,will that one db difference (lower formodulated signals) also hold true whenthe same meter reads a *1 dBmV sig-nal (CW), which would (you suspect)now be 0 dBmV for a modulated carri-er'/
Do not jump to any conclusionsabout these questions. The real factsmay surpr ise you just a tad! In fact,previous information generally circula-ted in other trade publications mayhave been ueru much ,tn error, as weshal l see.
Most ol the CATV industry asslLmesthat there is an auerage correction fac-tor of 1.0 db for CW carrier to modula-ted (AM) carrier readings. That is,most people assume that if the meterwas aligned to read *10 dBmV (real
I
MC-50 Specs
Frequency Range . .4 300 MHzOutputCapability . . . . +50 dBmV max
-10 dBmV minCon t ro lRange . . . . . . l dbs tepsAmplitude Accuracy . . . . .+ /-0.25 dbAmplitude Modulation . horizontal sync
pulse,50o/oCarrier Stability . . . . . .5 kHz drift maxLevelControl . . . . .closed loop system,
meter monrtorOu tpu t Impedance . . . .T5ohmsWeight .10lbs.Dimensions . . . .11"W, x 7"H, x 11.2"DPower Required . . .115 VAC,40 wattsPrice . . $695.00Manulacturer . . . . . .Mid-State
Communications, Inc.Rox 203, Reech Grove, Indiana
46107
level) with a +10 dBmV CW carr ier,then when you take that meter andreird an identical level moduhted TYcarr ier, i t wi l l read *10 minus 1 db or*9 dRmV. In other words, a carr ier,modulated, these Tteople tell you, sub-tracts 1.0 db level f rom the signal pres-ent over.a straight CW reference car-rrer reaorng.
Thi,s m,au not be crtrrect.Basical ly, one wonders uthy SLM/
FSM meters are aligned on CW car-rler.s for absolute (i.e. true-level pur-poses) values. How many t imes a daydo qou si t down and measure CW car-riersl Most of your readings are of(visrrirlly) modulated TV car-rier"s,whether they come from off-the,air TVsignals or local ly generated ( i .e. modu-lator-derived) sources. And with mod-ulat ion present, we have a normal si tu-ation where a carrier plzs amplitudemodulat ion is the norm-not the excep-tion. Yet most (if not all) meters appar-ently exit their respective factoriesaligned for absolute level reading ac-curacy with a straight CiV (unmodula-ted) carrier. Seemingly, this may bethe reuerse of real life. Why not alignmeters with a reference signal genera-
1 0
tor that has uideo modulntion present,which means that a *10 dBmV abso-lute level, to the SLM, would dove-tailor coincide with the kind of *10 dBmVreal-life signals you, the user, will bemeasuring in the field ? Then if youwant to add a correction factor foryour system-secure CW carriers (pilotcarriers for example), and your auralcarriers (FM modulated), such as add-'ing 1.0 db for any levels read to derivethe real-life levels on your meter face,you can do so. Measuring pilot carriersand aural carriers is in the minoritg ofal l measurements made; so why notLimit the correction factor to the minor-'i,t,u measurements, rather than the ma-ior i ty ( i .e. v isual carr ier with modula-t ion) measurements?
These questions raced through ourminds (some crawled rather thanraced!) back last fall as we preparedthe ser ies on SLM/FSM instrumentsfor CATJ. And as noted, we wonderedin pr int (aloud as i t were) on Page 29about these condit ions.
With our mouth open, one manufac-turer of CATV instruments took us upon the "chal lenge," and the result isthe new Mill-State Communications,1zr:. MC-50 Meter Calibrator.
The Basic TV Video Signal
Ver.y very basically, the relativeampli tude of a normal TV signal, amp-l i tude modulated, appears as shown inDiagram 1. The horizontal pulse/syncpulse levels are averaging higher inlevel than the highly varying video in-formation (modulation) content of thesignal. A white TV screen has a modu-lation depth (or percentage) of 87ol0.
DIAGRAM 1
CATJ for
L
Ilecausc picture content on any TVscene changes almost continuo-uslt1,you are experiencing constant ly chang-ing percentages of v ideo modulat ion onanv picture received (except of coursecolor-bar patterns, ID sl ides and soon). Therefore transmit ter engineersdeal in the world of averages, not ing asthe.y will that between 40 and 50o/onrodulat ion is present on the uueraga.
SLM/FSM manufacturers incorpor-ate into their instruments a peak-read-ins deteclor. which is a bi t of a mis-nomer r ight of f the bat. A true peak-reading detcctor would read only thepeaks and displav only the peak modu-laLion (* carr ier) levels present, rht'r.u,l tine.. However, real t' im,e is a bitI'ast for you or mc to track the meter-needlc movement (and a bi t fast for thenret,cr-nccdle movement to track inz'r,rr1 li lc), because of ther al'orcment, ioned constant ly changing picturr, 'content, , /v ideo modulat ion percentagepresent. So the peak-reading detector(a diode fypically) dnes reatl, peold:;, buLdirect,l.y o,l'ter'f,he detector that rend.sp e o,l t s is ir c h u,r q itt 11.c. op acit or ( D ia gram2) which hokls Lhe peak reading fromthc detector for some Deriod of timet s m l l l ) u n t i l t h t , n e x l p e a k c o m t ' s a l o n g(i.c. the ncxt cycle). ' lhe chargitt4J cep(r-c'itorin el'fect a,I)ereqes (maintains) thepcak, taking the peak present in onecycle i rnd hokl in,q r . l unt i l the next cycleoccurs. Thus the reol pea,k tl,etectoris zr combitrnt,irn. ol peak reading ando,uereqe sustaixlixl(J, through the cctm-ltinati,on of the detector (diode) and thecharging capacitor. And the basicproblem with this scheme is obtainings'u.l.l iciettt d,et,ectctr energA to chargethe capacitor and to hoki that charge inthe capacitor without bleeding off thedetected horizontal sync pulse beforethe next pulse is created.
The charging energy for the capaci-tor tied to the aft end of the detectordiode is a very imporiant source forerror. Most SLM/FSM instrumentshave a 20 db meter scale width (Sadel-
J U N E , 1 9 7 5
D ET ECTO RD I O D E
DIAGRAM 2
r . :o nretc 'rs hnve a 30 db + meter "win-
dow"). A 20 db r i lnge is a 10 to 1 vol tiigc change or range, through uthidtthc nreter detector must funct ion. Arr.rcl.t-'r with 1.0 volt on the detector atlL r l l sca le has 100 mV on i t a t m in imumst:alc, 1 'or cxample. To maintain an adc<lrratc r:/inrcle-hoklin91 tim,e peri,od (cyclc) lor the delector/charging cerpaci-tor, thc mc'ter designers try. to maintiiin ir ver.y high impedance Lood on thedcLcctor/charging capacitor combina-Lion. In the proccss of al l o1' this, thclincirrit,y ol' thc detector/capacitor<ronrbination is d.i,st.ortetl so that in reo.l.1ilc thc detcctor c'fl ' iciency (i.e. thc rater>l' corruersi.rnr of input RF level to outpul D0 voltage) is lower for lower input, (Rtr input) levels to the detector.' l 'h is is ono ol ' the major contr ibut ingI'actors which aflect ecc'uru,clt ol' absolutc lcvel mr)asurcments in prescntday CATV instrumcnts. And this is acontr ibut ins factor to the meter mnnula<:trrrers, urging all users to reatl, alt-sttl 'ule k:t;els in the top 5-10 db port,i,ortol any meter scale range the.y may hap-Jren to be using; in ef l 'ect, keepingrcadings which must be accurate in thetop portion of the scale (o.n rl scole.),wherc all meter design factors, ittclud,-itrq rlttect.or eJJici,en,ci;, are optimizedlor ar:curate performance.
The Basi,c MC-50
The basic MC 50 meter calibrator1'rom Mrd-Sta,t,e Communications, Inc.recognizes these inherent problemswith al l instruments. What Mid-Statehas done to make life easier, and moreaccurate, for you as a signal level me-ler user'/calibrator is to provide vou
C H A R G I N G
T
CAPACrroR
t l
P I NL E V E L +I l lODULATOR
LOW PASS
F I L T E RA T T E N U A T O R
DIAGRAM 3
with a tuneable reference signal generator that has both straight CW (A0)carr i ()r output, and at the push of ahutton, 50o/o (simulated) modulatedcarr i ( ' r output.
' fht ' MC 50 ut i l izes a high output( levcl) tuneable osci l lator that coversthc l ' ret luency range 4-300 MHz in twobands: from 4 150 MHz and from 150-ll00 MIIz. 'I 'he desired operating fre-( luoncy is selected by the user, by sim-lv select ing the proper band and rota-t ing lhe largc front-panel knob to thedesircd carr ier f rer luency where theSLM/F SM wi l l bc al isned. The whitecircr.r lar dial is marked in frequencies(5 MIIz increments) trnd in VHF chan-nels (plus mid-band and super-band).
Thc tuneablc local osci l lertor is mixedu, i th a f ixed frer luency (CW) osci l latorin a double balanced mixer. The f ixedfret luenr:y osci l lator is where the simulated 500/o video modulat ion takesplace (sec Diagram 3). A level ing loopcontrols a pin diode leveler, and theresultant s ignal is monitored by a hotcarr ier diode and displayed on a front-panel meter. Simi lar in concept to the
1 2
Bolonreter circuit on the Measure-rne?t ls 950 signal generator (see Pagesil,1 37 ior January CATA, the meterdisplav is a go no-go si tuat ion. As longas the meter displavs thc needle in ther:enlr : ' r port ion of the scale, the sel f-bal-ancing leveler circui t is operat ionaland thc cal ibrat ion ol ' the unit at theI 'a<' tory is maintained in operat ion. Anydcviat ion of the meter needle from theccnlcr port ion of the meter display iscausc lr l r concern; in ef lect, the meters('rves &s Lr u)Q.T"ni.nq sustem. that something has !{one awry in the unit .
The MC-50 Meter Cal ibrator has an)i ix inrum output level of *50 dBmVwith two l'ront-panel step attenuators(rotary). One rotary has six posi t ionsin 10 db steps (0-50 db of at tenuat ion),whi lc the second has 10 posit ions in 1db steps (0 10 db.of at tenuat ion).
The digi tal modulat ion circui t , dutycyclcd to represent 50olo aDerage mod-uktt iort keyed to the horizontal syncnulse. is connected into the level con-irol circuit to ensure that no changetakes place in the peak carr ier levelu;hen rtotl,ukttiltrt is stpitched on.
CATJ for
il
TABLE ONE
Five meters in the CATJ lab at the time the MC-50 anived were checked for themeter- indicaled dif ferences between an A0 (CW) carr ier, wi lhout modulat ion, and amodulated carr ier as provided by the MC 50. These tests were repeated at ful l meterscale, mid-scale ( i .e. L0 db lower), and low end of scale ( i .e. 20 db lower than the f irstlevel). Thus we repeated the test three t imes with each meter (six t imes with the B-TFSM-Z as shown) to get an indication of not only the meter-reading dif ference between aCW and modulated signal, but also an indication of how meter detector eff iciencychanges throughout the meter-scale range.
Meter Fu l l -Sca le D i f fe rence * Mid-Sca le D i f fe rence Bot tom-Sca le D i f fe rence
Je r ro l d 727 1 .1 db 1 .6 db cou ld no r measu reaccu ra te I v
B.T FSM-2(1 ) Peak 1 .3 db 1 .9 db cou ld no t measu re
accu ra te ly(2 ) Ave rage 2 .8 db 1 .9 db cou ld no t measu re
accu ra te t vBenco FST-4 3.0 db 3.0 db 3.0 ooSade l co FS-3SB 1 .0 db 2 .0 db 2 .2 dbM id -S ta i e SL IM 0 .1 db 1 .0 db 2 .0 db* Di f f erence was always lower indicated levels when modulat ion was added; theref ore tvpical users
wou ld add d i f f e rences shown above (when ve r i f i ed f o r t he i r own i ns t r umen ts ) t o ob ta i n t r uepeak read ings w i t h v i deo modu la t i on p resen t .
IF
Recause of the relat ivel .y high outputlcvc l p resent (+50 d l lmV max imum) ,thc MC 50 wi l l do duty not only as anSLM/FSM cal ihrator but as a general-purpose signal generator and as a var iable l rcr;uenc.y marker generator foryour swecp-system test ing.' Ihe' operat ing vol tages within theunit arer +/- 15 vol ts DC and */- 7volts DC. Thc */ 7 vol t DC supply ispr inrar i lv to run the clock refercncesyst( ]m; nrost of the innards funct ionlronr thc */ 15 vol t DC supplv l ines.Thc un i l d raws 40 wat ts on 115 VAC.
Q'ue s ti r ttt.s /An s u )er s
In our introductory remarks for thisreport , we asked quest ions aboutthings such as "what are the real- l i fedi f ferences between CW carr ier read-ings and modulated TV carr ier read-ings' /" And "how does the typical peak-rei iding detector meter handle thesedifferences at uurious detector input(RF input) uol tage leuels?"
J U N E , 1 9 7 5
When thc MC-50 was received atCAT,I, we promptly set up the unit tochcck the operat ion of four di f ferentinstruments we happened to havearound the lab. The results of thesetests are shown in table form. Notethat we made comparat ive checks ofLhe d.il'l'erentt: in intli,co,ted, a,bsolut,eIeuels I'or CW (A0) carrier and videomodulirtion carriers al" three po,ints f.or
M I D - S T A T E M C - 5 O M e t e r C a l i b r a t o r / S i g n a l G e n -e r a t o r f e a t u r e s b u i l t - i n s e l e c t a b l e v i d e o m o d u l a t i o n
1 3
each of the f ive instruments on hand.These checks are for indicated differ-ences in level for CW and modulatedcarr iers at -10 dBmV, 0 dBmV and+10 dBmV levels. These are notchecks of the individual meter 's abi l i tyto accurately read the absolute levels(we did that in November/JanuaryCA'1',Il; this check is onlu for the rliJfer'et tr : t ' in indicated levels for CW vs.nrodulated carr icrs.
A check of Table 1 clear ly indicateslhat given this type of test procedure,lht t:rrriott.s meters utun,t to read lessolt(l l,?ss o,t:curute (i.e. the diflerencebct,lver:n CW and modulated carrierbct:onrtrs greater) o,s the m,eter-scaleTxtr'l ' irttr ul' i l i.zed i,s retl,uced,, with rareexceJrt ion. In al l cases, the meter scalcr,r 'as l t . l ' t , intact; reading in the 10 to*10 dBmV resion. The tests translateinto dt' t t:cl rtr-efJi,ci,en cq errors, and theerrors tvpi t :al lv bc'come ol progressive-lv larger nragnitudc as the detector in-Jrtrt. volt,agc bt:contes ktuter and, ktuter.This is r t ,ol intended to be an acrossthe-board indictment of the meters(nrost nl l sul ' l 'er , in varving degrees);we did that on an individual basis inNovcmher/January CATJ. This is in-ternded rather to point up the utili,t-t1 oftht: MC-50, and hou; with this instru-ment, you can ei ther cal ibrate your me-ter properly for modulated TV carri-crs, or lacking the expert ise or t ime tore-cal ibrate the SLM/FSM, at least de-velop a pasle-on the- instrument cal i -brirtion correction table for that par-t.i t-.u.h r i,tt s l ru,m,ent.
S/A I)isple! Puzzling
Natural ly, we wanted to see whatthe cf lect of the CW carr ier vs. modu-lated carrier switching would look likeon a spectrum analyzer. So we trottedout, the Terscan VSM-1 (see JanuaryCAT,I, Pages 41 50)and checked for (1)carr ier stabi l i tv when modulat ion wasadded (Mid-State says i t wi l l stay with-in 0.25 db), and, (2) harmonic outputcontent of the MC-50.
1 4
V S M - 1 D I S P L A Y o f 5 0 M H z o u t p u t f r o m M C - s O( f a r l e f t ) , 1 O O a n d 1 5 O M H z h a r m o n i c s ; b o t h a r ed o w n m o r e t h a n 3 0 d b ( 4 0 d b l o g s c a l e )
When the MC-50 was connected toLhe VSM-1 and the carr ier level ad-iusted for ful l screen displav on theVSM 1, the modulated signal was ap-pl ied. Son of a gun, i t appeared to usthat thc carr ier level actual ly dropped,perhaps a db or so. Hummm. We tr iedi t several di f ferent t imes at di f ferentinput levels to the VSM 1 and f inal lydecided the MC-50 had a problem; sowc called Larry I)olan at Mid-State.
"Per.ft:ct.I.t1 notm,a,L, " said Dolan. "The
problem is in the VSM-L," he ex-plained. "Ifout's t,hril againl " we asked,patt ing our VSM-1 lovinglv. "Look, theVSM t hus tt, mu,qn,etir d,eflection, sus-tent, e,ni, tlte uolrc on the CRT clisphgrt,r:Luo,LLtt roLLs oJJ' the response so that, a15.750 lcHz mod,ulalion (which is whatthe MC-50 uses) ?l)o?re,/orm is d,outn ont,he response curue of the !.toke re-sponse. If you tru the so,m,e test, on auitl,e-ltcLn,d, sco1le uti,t.h just a quickie d,e-tector suclL as Steue Richeu tl,escribedin the Morch CATJ, " said Dolan, "you
u)o'uld, see that the carrier Leuel, utithmodulntiott presertt, rl,rtes not deuiatem.ore tho,n the 0.25 d,b ute spec the uni,ta t . "
Which we did, and which i t did. Butwe thousht we should mention thishere because sure enough somebodyout there would connect the MC-50 to aVSM-1 type machine and immediatelyassume the MC-50 was not holding a
CATJ for
constant output (+/- 0.25 db) when15.750 kHz modulat ion was switchedon.
Now Mid-State specs the harmonicoutput content of the MC 50 at -30 dbreference the desired frequency car-r ier, or bel ter. Because harmonic out-put content has some bearing on theuseful output energy level which theSLM/FSM sees for cakbration nur-poses. we che<.ked this with LheVSM 1. The photo shown here depictsthe pr imary output signal at 50 MHz,and the harntonics at 100, 150; no har,monics above the third at 150 MHzcould be detected on the VSM 1.
As Mid-State points out, the MC 5{)is cal ibrated on a power meter (as al lreference signal generators must be),and through adequate precaut ionswith bandpass [ i l ters between theMC-50 output and the power meter in-put, the effect ive power level present
from any harmonics of the fundamen-tal (desired) frequency is for all practi-cal purposes ignored by the power me-ter; such energy is just too far down onthe skirt of the MC-50 plus bandpassf i l ter combinat ion to have a consequen-tial influence on the accuracy of thepower meter indicated level present.
SArutpsis
At tr time in our industry when manysuppl iers are hesitant to invest in newproduct - research - and - developmenttime, it is refreshing to see not only thed,ereLopment of a new product such aslhc MC 50, but to note with some plea-srrrc that the whole project and prod-ucl t t rrned around from a CATJ queryon Page 29 'in Januarg to a working,production box in late Marchl Nowwith that kind of dedication and crea-t iv i ty, the CATV industry wi l l bearound for a long long time to come!
LOW COST S/A_IN JULY
The July issue of CAT,I wi l l includea detailed report prepared by JerryLnufer, Engineering Manager for Gi l lCable, Inc., San Jose, Cal i fornia, onbui lding your own spectrum analyzer.
No lti,q d,enL-Jerry has taken a Jer-rold RCS-3 home converter, a signallevel meter and a (we show you how)shop-bui l t sawtooth generator andplugged them all together into asmooth running package that withyour shop (DC) scope makes a spec-
trum analyzer. Total cost perhaps$50.00 i f you have the basic sub-parts.
The July CATJ wlll tell you all aboutthis reader-developed piece of tester luipment, including complete con-struct ion detai ls, board layouts andnumerous photos of the device, inter-connect ions and scope screen displaysof the box(es) in operat ion.
II you want to prepare for it, rundown .your local Jerrold man and talkhim out of an RCS-S converter for a
J U N E , 1 9 7 5 1 5
COLOR.ADDER CONVERTSWEATHERI MESSAGE
CHANNELSTORED,WHITE, BLACKDISPLAYS
Rerl Is Bright
If your black-and-white weatherchannel has been plugging along formonths or years with no more atten-t ion than most . . . and i f you are look-ing for a way to l iven up the channel(short of running "X" rated sl ides atthe end of the scan), here is a quick andc:rsy rainy day project that will turn.your whites nnd grays to a bettershade of pink (or red).
Tht> Color Adder is a simple "fool thetelevision set" box that plugs into thecoax l ine between the output of thevidicon camera (video output) and theinput to the CATV channel modulator.It operates on the principle that forthere to be color reaction in a colorreceiver, the "transmit ter" must radi-ate a ll.58 MHz (rounded off) sub-carri-er. So the Color Adder does just that:i t generates a 3.58 MHz carr ier whichis mixed (or added) to the vidicon cam-era video output on the way to thechannel modulator. At the customer'sreceiver, the receiver detects the pres-ence of the 3.58 MHz (sub) carr ier, be-lieves it is receiving a color sub-carri-er, And immediately turns on the colorguts of the receiver. In the process,anything the vidicon camera sees be-comes subject to the 3.58 MHz (sub)
bl-t,S.K. RicheyRichey Deuelopment CompangOklahoma Citg, Oklnhoma
1 6
Key lt Bright
carr ier; the net result is that the so-called gray scale from just a shadedarker than white al l of the way up todark gray becomes a shade of red (orp ink i f you w i l l ) .
In addit ion to gett ing a white (moreabout that short ly), pink to red andblack display Jrom o black-and-tohitecomer'(4 it is the observed opinion ofseveral system operators who havetr ied Lhis circui t that you can sharpenup the black and-white detai l of thevidicon camera picture display on acolor rcceiver by running the ColorAdder at a low level, too low to actual-lv provide zr color tint on the grays.
One IC
There is not much to the circui t ; i tgoes easi ly into a mini-box. The basiccircui t is nothing more than a 1702Qu.ad tu;o input positiue NOR gate ICdevice. Added to this (see Diagram 1)is a 3.579 (etc.) crystal (commonlyavai lable these days), and a smal lhandful of miscellaneous iunk-box-typeparts. A 500 ohm pot allows you tocontrol the level of 3.58 MHz injectionfrom the oscillator to the through lineof the vidicon camera video.
Construction is simple, and all partsshould be available locally. The type402 trimmer is a 5-25 pF mica compres-sion trimmer; any other variable capa-citor that will tune this range should
CATJ for
f rooor
I C I S 1 7 0 2 O U A D , 2 I N P U TP O S I T I V E N O R G A T E
DTAGRAM 1do the iob. I f you want to put togethera I 'C .board, a foi l s ide layout is in-cluded here, actual s ize. Simrr lv use i tas i t appears in CATJ to expose yourown board. O., you can wire the unitup as shown on i ln appropriate ICsockct with hard wir ing.
' fhe power requirements are veryminintal : 5 vol ts DG is required. Usethe schematic shown in Diagram 2, orvo l t i rge drop I ' rom an.y s landard 6 vo l tsupply you may have kicking around.Even a battery source wi l l do, al-though the battery life will not be veryh i s h .
I lR5f l [ , . -^, ,"13"%Bii^,"" ,
Installation is very simple: insertthe Color Adder into the uid.eo Linefrom the camera on .your weatherchannel, message channel, etc. as i tgoes to the CATV channel modulator.Thc 500 ohm pot in the Color Adder isused to control the amount of 8.58 MHzosci l lator s ignal that enters the modu-lator along with the vidicon cameravideo information. And this is anotherwa.y of sa.ying that as you vary the 8.58osr , i l l a to r s igna l leve l . upwards . theamount o1'color showing on the receiv-er increases. I t has bee-n noLed that i fyou crank in just enough 3.58 oscillatorto key on the receiver color circuits,buL rutt quite enouglr to start the tint-ing process, the qual i ty ( i .e. def ini t ion)ol ' the black-and-white (unt inted)image on the weather (message) chan-nel improves noticeably. Apparentlythe TV receiver l ikes the presence of
fx""r;"1 N 7 5 2 0 R
V O L T Z E N E R
DIAGRAM 2
tJ U N E , 1 9 7 5 1 l
a#JgnIthe 3.58 sub-carr ier, and the video de-tector and associated receiver videoamplifier circuits perform better withthe color osci l lator switched on. As yougo beyond the point where the 3.58MHz receiver osci l lator just keys on,the ermount of red tint to gray objects,backgrounds, etc. increases. You neverreach a ful l red (unless vou ki l l thevidicon camera video level and haveiust a blank raster; then you have abright red!) , but with the 3.58 level setby the 500 ohm pot in the Color Adderat a point where white areas.iust startt,o to,lte ort a pin,k tint, the gray scale(from light tiray or off white to darkgray, or almost black) tint up fromlight pink to dark pink, respect ively.
A really critical person would noticethat with the Color Adder on, white( i .e. pure white) is no longer possible;i t takes on a sl ight pink t int . This mayor may not be to your liking. Of courseyou control the amount of pink fromlight to dark with the 500 ohm pot, butthis is a subjective thing that everyCATV-connected set in town will haveto cope with on their own as they dis
DIAGRAM 3
cover your new toy and start crankingaround their own "tint controls" Iook-ing for blues and greens!
One way to make the whites comeback is to design a diode level detectorthat senses the presence of pure white(maximum video level) , and operates aFET switch to turn off the 3.58 MHzosci l lator when ful l white is diode de-tected. This would allow you to run thegamut from black to reds to pure whitewith not much more invested than thesimple Color Adder circui t shown here.This has not been done to date by theauthor, however, s imply because weare stil l in the "Gee, look at those redpictures" stage.
One fellow we know got so carriedaway when he bui l t up his own ColorAdder that he directed his secretary togo down and purchase some Hot Pinkl ipst ick. After applying the l ipst ick ( toher, not him!) he ordered her to plant abig set of lip prints on the face of sever-al of his weather instrument glass cov-ers. Now when the camera pans theinstruments, the background of thewhite meter is very sl ight ly pink, thelettering and needle are black, andstanding out there in front are two"Hot Pink Lips."
Whateuer tur-ns you on,!
The May issue o f CATJ. Page 1 1 . con ta ins a schemal icdrawing o f C C0R's bas ic s tandby power s ta t ion and thein te rconnect ion fo r same. In the d iode br idge, the d iode0n the sou lheas l quadrant (up is nor th ) i s reversed 180degrees . Turn i t a round or i t w i l l se l f -des t ruc t . Th is e r r0 rwas in CATJ dra f t ing , no t C-C0R presenta t ion .
1 B
The same May issue, Page 34 , g l ib ly d iscusses thepr0posa l tha t the 1 050 sweep mach ine cou ld be ex terna l l y' ' j acked" fo r d i rec t DC power ing f rom the cab le sys temampl iJ ie r . o r " jacked " fo r power ing f rom the 30 /60 VACl ine supp ly Ac tua l l y , DC power ing w i l l n0 t f l y becausethere is n0 60 cyc les I0 r the sweep hor izon ta l d r ive t0 thescope. But a manufac turer cou ld p rov ide a tapped 1050(e lc . ) AC t rans former in the i r un i t wh ich wou ld accept30 /60 VAC as we l l as 110 VAC and the scheme wou ldwork .
;I
I
00Ps
CATJ for
ANTENNABASICS(Part One)
vl44_!:Antennas play such an important
role in our everyday CATV l ives, abasic understanding of what they areand how they perform is essential forevery level of CATV personnel.
Most TV receivers have bui l t - in an-tennas. Many of our CATV-connectedhomes have (or had) rooftop antennas.And we have antennas. Short of cable-connect ing direct ly to the signal source(i .e. the transmit ter) , the antenna is anincscapable part of the broadcaster-to-rcceiver erluittion.
There are two antennas of concernin the broadcaster-CATV equation: theantenna utilized by the broadcaster tort-'ach us, and the antenna employed bythe CATV system to inter-connect thebroadcaster's signal with our cabledistribution facility. The broadcaster'santenna is fixed, and beyond our con-trol. Our antenna on the other hand isas flexible and variable as our financesand physical surroundings will permit.
Any antenna is an electrical circuitof a special function. An antenna is aresonant circuit; that is, the combina-tion of all of its physical parametersresults in the antenna providing peakor maximum performance in a specificfrequency range. In this regard it doesnot differ markedly from an amplifiercircuit. An amplifier circuit util izes acombination of inductance (coils), andcapacitance (capacitors) to determine aresonant (or operating) frequency for
J U N E . 1 9 7 5
Summer Antenna Series
the amplifier. There are broadbandedampli f iers ( i .e. covering a wide rangeor band of frequencies), and there arennrrow-band ampl i f iers ( i .e. coveringjust a single TV channel, as in CATV).The circuit designer of the amplifier"plays" with the parameters (induc-tance and capacitance) until heachieves the desired (design intended)results.
Now a coil and capacitor combina-tion resonernt on (say) channel 2 isrluite small. You can hold it in the palmof your hand with ease. Yet i t is de-sign- intended for channel 2. A channel2 antenna, on the other hand, is muchtoo large to be held in the palm of yourhand. And the di f ference is this.
The d,imensi,ons of the coil(s), capaci-tors, and connect ions in a channel 2(amplifier) resonant circuit are sosmaLl, as compared to the actual physi-cal length of the channel 2 wavelength,that radio frequencg (RF) energy inthe circ'uit is primartlg utilized in theperform,ance of the circuit goal (al-though some is dissipated as heat).
However, if the circuit designer be-gins to "play" with the characteristicsof the resonant circuit, increasing theinductance (L) of the circuit so that thephysical dimensions of the "circuit" be-come large(r) as compared to the actu-al physical length of the channel 2wavelength, some of the energA in the
t1 9
] P A I L O F
4 { i n I l o N s t z F
DIAGRAM 1
t:irt:uit. e,sce,pes from the circuit bq rad,i,-tr,tiort, ol electromtrgnetic waves.
( ieneral ly speaking, the amount ofsignal vol tagc intercepted by i tn untcnna slanding in the atmosphere is alrrnct, ion of l lLe si .ze ol Lhe antenna. Forour purposes, i t is convenient to visu-al ize lhe signal t ransmit ted by thebroudcastcr as being omnipresent (ev-c'rywhert- ' at the same t ime). We of( 'ourse know that broadcast signals nret ru l t ' t l r t t t l l r l p t ' ( ' s ( 'n l bch ind hu i l r l ings .hi l ls, or in val loys. But within tr smaLLorcn, such as at our headend si te orwithin the cone ol ' inf luence of our tower srrpport structure, we can J'or oI IpructicoL p'urposes conclude that thesignal we are desirous of receiving isavai lable anyplace we might happen tornount l rn "antenna."
So i t is also convenient to view ourreceiving antenna problem as one ofobtaining suff ic ient "signal l low" ( i .e.voltage) to meet our minimum require-ments for s ignal strength ( level) . Andfor our purposes, we can draw an anal-ogy between our antenna system and awater catchment system (see Diagram1). Visual ize each antenna as a pai l setout on the ground to collect rain water.The more pails, the more water collect-ed. Or, the more antennas, the moresignal collected. Or, if four small pailsmake less sense than one big pail,where the sum of the open-face diame-ter openings of the four pails would bethe same as the open-face diameter of
20
one larger pail, then it may be moreconvenient to catch our water (or sig-nal) with one large pai l (antenna) thanfour smal l pai ls (antennas).q!!l!41'
In an electrical circuit that has res-onance at a particular frequency, theinductance (L) of the circui t is pr imar-i l .y concentrated in the capacitor, andthe resistance of the circui t is spreadt,hroughout both of the L and C concen-traLions, plus throughout the connect ions of the circui t . This is cal ledlurrtyterl, ctnt,stonts, because two of thernost in iportant ingredients which de-ternr ine operat ing frequency arebunchcd (or lumped) together in singu-lar c ir<:ui t locat ions.
In an antenner circui t , the induc-lancer, the capacitance and the resistance tre spreerd rather uniformlyLhroughout the whole body of the an-tcnna. This is cal led distr ibuter l con-s Irnr l s.
In an antenna circui t lhere is bothrcsistance and reactance. 'I 'he largestreceived signal vol tages wi l l be pres-enl when the resistance of the circui t isLuned out, or minimized. Which is an-oLher wa;, of saying that largest re-ceived signal vol tages wi l l be presentin a given antenna system when thes.ystem circui t is tuned to resonance atLhe operat ing frequency.
Resonqrrce
If the voltage we desire from thesignal we are receiving is our pr imaryconcern (and i t is) , we need to know alittle bit about the resonance charac-ter ist ics of antennas.
- I / 2 R F C U R R E N T+ C Y C L E
/- -\-t\
/ / ' \1 / 2 ̂ L o N G
r l
DIAGRAM 2
f t\ \\ t\ )t l
A BS O F
L O N S I Z E
J I) tt /t lg B
4 P A I L
] G A I
iCATJ for
tl-"-l l-____ 1/2 wAVELENGTH
DIAGRAM 3
As shown in Diagram 2, the shortestantenna-conductor which wi l l tune torcsonance is a r/z wavelength antenna(the actual antenna mater ial may bean.y conduct ive medium, includingwire, tubing, etc.) . A r /z wavelengthantcnna is iust long enough so that theeleclr ical impulse on the desired fre-( luency wi l l t ravel f rom one end of theantenni l -conductor to the opposite end,and hack asain in the t ime i t takes forone I IF cvcle to pass.
Cal<rulat ion of this "shortest pract i -c r t l l cng th" i s r t ' l u t i vc ly s imp l t ' . For a l lpr i tct ical purposes, RF waves travel atthc spced of l ight, or 300,000,000 me-ters pcr second. ' fherefore the dis-t ,ant:c which Lhe signal wi l l cover alongI r pcr l i ' r ' t l rn l t 'nn l r s t ruc lu re i s cqua l tot h i s v t , l o r . i t v d i v i d e d b y l h e l r e q u c n c y :
% wavelength - 3oo.o-oo.ooo
whert- ' the answer is in meters and f isthe l ret luency in hertz. This can benumerical ly shortened by using the de-r ived formula:
72 wavelength = : ; !?,? :f ( M H z )wht-.re instead of meters we have theanswer in feet.
Now these formulae (rssume that theRF wirve will travel along the surfaceoJ' t,he cm,tenno utith the same uelocitgor speed as it will in air. The facts arethat this wi l l not happen, because thedielectr ic constant of the antenna ma-terials is trlways greater than theequivalent air constant. Which is an-other way of saying that the surfaceresistance of the antenna mater ial(s)acts to sktu; cloun the speed of thetrrnr.,e passing along it. The net result isthat when you design an antenna thatis corrected for the dielectric constantof the antenna materials. vou have an
J U N E , 1 9 7 5
antenna that is physically shorter(smal ler, etc.) than a paper-designedantenna that assumed ideal condit ions.
So you must correct for the effects ofthe antenna mater ials, and you do thisby modifying "492" in the llz wave-length formula iust given by some cor-rection faclor (call it k). The formulathen becomes:
4 9 2 x k% wavelength =
and now we mustv r t l u t ' t o l Lss ign to k .
f ( M H z )
determine what
K, as a physical- length-correct ion-factor, is dcpendent upon the rat io ofthe antenna surface conductor lensthto i t s d i l rmct t ' r vs . openr l ing f requen-cy. Sr:e f)iu,qrrtm 3. As this rati,o be-comes s'muller rnri, smnllet', the morcLhe ph.ysical anLenna we are construct-ing nirr.sl shtrtett tct t:ont,pensate lor anincreasing sur lace area of the antennae lement .
Another way of stat ing this is tonote that as antenna construct ion ma-ter ials incrc 'ase in physictr l diameter(size), the greater the shortening ef-fect on the physical length of the an-Lenna. i tsel f . In actual pract ice, anten-nas consLructed in the VHF/UHF ret{ ion with nntenna elements of 0.25 to2.0 inch diameter often are as much as1l-7olo shorter in real life than the sameantennas would be i f constructed from#12 wire ( for example). The f inal resultof taking into considerat ion the "k fac-Lor" is yet one more (and more f inal)formula for determining the actuallength o l a resonant an tenna fo r VHFand UHF frequencies. Because anten-na-elements lengths tend to becomequite smal l at VHF and UHF frequen-cies, it is usually more appropriate toreference lengths to inches rather than[eetlmeters and fractions decimal frac-tions thereof. The formula thereforebecomes:
Length ( in inche ' 5905 x kst = -lffiplr1
although this stil l leaves us unsure ofthe influence of "k." Reference is made
2 1
I +7 f
(p o .oe{r 0 . 9 4Y
1 . O
1 0 2 0 5 0 1 0 0 2 0 0 s o o 1 0 0 0 5 0 0 0 1 0 0 0 0
R A T I O O F I ] A L F W N V E L I N G T I I
T O C O N L ] U C T O R D I A M E T E R
TABLE 1
to Table t here which indicates a valuefor "k" based upon the ratio betweenthe antenna-element diameter ( ininches or fraction thereof) and the freespace r/z wavelength lor a particularfrequency. Table 2 here indicates thepract ical ef fects of 0.25, 0.50, 1.0 and2.0 inch outside diameter elements ona resonant r/z wavelength dipole forchirnnel 2 (55.25 MHz), 7 (175.25 MHz),i rnd 14 (471.25 MHz). As is evident,antenna physical length is progressive-l.y determined as the frequency risesb.y the diameter of the mater ial ut i l izedin the construct ion.
Final ly, i f a l l of this seems too purefor average everyday zrpplication,there is a formula which cetn be em-ployed t.o tl,etennine the length of thed,ipoLe elem.ent u;i,th reasonable accura-r-'?, which includes an "average" valuelor the k fuctor. I t is:
Length in inches =
Matching
f ( M H z )
A resonant antenna is, as we haveseen, resonant on one single frequen-cy. And that frequency is the sole fre-quency where RF energy, encounter-ing the antenna, will travel from oneend to the opposite end, and backagain, in precisely the time it takes forthe RF carrier wave to go through onecomplete carrier cycle. To put that intoperspective, at channel 2 there are
22
55,250,000 cycles of carr ier wave persecond (whi le at channel 14 there are471,250,000 cycles of carr ier wave persecond).
Flaving the antenna resonant is thef i rst reouirement. because resonancecorrelates with maximum energytransfer from the transmission med-ium (air) to the antenna col lector (di-pole). The next requirement is match-ing of the impedance of the antenna tothe transmission l ine. Antenna res-onance is important to the bransfer ofelectromagnetic energy from the air-transmission-medium to the antenna,and antenna impedance matching tothe impedance of the transmission l ineis et lual ly important for t ransfer of theantenna-captured energy to the trans-miss ion l ine l ink to our rece iv ing er lu ip -ment.
No barsic dipole antenna is just outo-rrLotit:ulltt 75 ohms, unbalanced. Yet ourmost standard transmission line for-mart is exactly that. Therefore toco'uple the m,ax'imum amount oJ anten-rtz-dipole energA out of the anten,rutorul'into t,he trrmsmission Line reouiressome lype o f impedance match ing ne l -work.
Impedance transformation projectsimmediately run into two separate butrelated problems. The first and mostobvious is the matching of a 250 ohmantenna impedance lfor example) to a75 ohm transmission l ine imnedance.The second, and no l qu iLe so ohv ious ,is the common antenna design practiceol bakmced antennas, and the almostuniversal-in-CATv employment of. un-bahnced transmis sion lines.
U
zzoUE
U
zF
2
E
I
TABLE 2Free
Space O.25" 0.50" 1.0" 2.O"
ch.2 8.90' 8.63' 8.59' � 8.54' � 8.46' �
ch. 7 2.81'� 2.10' � 2.68' 2.61' 2.61'
ch. 14 1.04'� 1.03' � 0.98' � 0.96' � 0.95' �
CATJ for
Inrpcdance t ransformat ion is a -transformer type of problem. You have 1/2rwrrH k FAcroRon one hand a known impedance of "X" I
value and on the other hand a known DIAGRAM 4
impedance o f "Y " va lue : and to coup lemaximum energy from "X"
to "Y," you f-- 14> ---|- r 4^ ------1need a ma leh ing t rans fo rmer no t un - -TNSUTAToRl ike those we hang dai ly on the back of ,custonler receivers. Or you need to - 1/2^wrrH kFAcroRemplov some special matching tricksthat are usually peculinr to
"antenna DIAGRAM 4-a
sttstems (i.e. they are not practical forbehind-the-set devices).
Btrlanced to unbalanced matching isI var iaLion of the f i rst problem. indoften both portions of the problem canbe tackled so that both are solved si-multaneously.
For now we wi l l stay with the basicantenna, the "dipole." See Diagram 4.This dipole antenna, adjusted to reso-nancg b.y tuning the length to exact lyr/z wavelength overall (with k factorincluded), is nothing more nor lessthan a straight metal rod of conductivemater ial . Connect ing the 75 ohmCATV transmission cable to the dipoleelement is no easy tr ick!
Wc have the fol lowing opt ions avai l -ab lc :
(1) Wt-' can break the 1/z wave-length rod into two exactlyet lual parts, placing an insul i rtor in the center as shown inDiagram 4-A; and treat each of
DIAGRAM 5
DIAGRAM 5-a
J U N E . 1 9 7 5
DIAGRAM 4.b
the two port ions as equals. Inthis case, equal l / tLh wave-length elements.(A) This can be fed with bal-
anced 72/75 ohm line,such as 75 ohm twin-lead,directly, and a good matchwil l result .
(B) This cannot be fed directlywith unbalanced 72/75ohm line, such asRG-59/U, .412, etc. be-cause the balanced anten-na will not present an un-balanced 72/75 ohm loadto the unbalanced 72/75ohm coaxial cable.
(2\ Or, we can leave the r /z waveelement intact and;(A) Connect the shield of the
coaxial cable directly tothe center of the t/z w&vE-length rod (same point asbroken at center in I1lahove), and through amatching arrangementknown as a gamma match(see Diagram 5), in effecttap along the dipole ele-ment until the correctnoint is found where the
23
DIAGRAM 6
unbaktnced impetlance ofthe transmission lineerluals or matches the un-bo.ktnced impedance of theoJf-center-fed dipole ele-ment.
'fo tune out residual reac-tance, a ser ies tuning ca-pacitor is added to thematching system asshown in Diagram 5-A; ca-pacitance values of 50-75pF are typical for low-band channels; 10-20 pFvalues are typical lor highband.
(B) lJsing an approach knownas Lhe T match, as shownin Diagram 6, the basicrt- 'sonant dipole is paral-lirl led for a portion of itsrun b.y a second set ofshorter antenna elements,which short or connect toLhe basic antenna elcmentwith sl id ing adiusl ingcl ips. The bottom, shortersection, i,s broken, in thecetfter antl Jed taith 300ohm. bakmced l;ine. Atsome point equidistantfrom the center of themerin antenna element,both shorting bars self ad-just to produce the bestmatch for the antenna ele-ment to 300 ohms, andmaximum energy transfertakes place ( i .e. bestmatch). Of course this st i l lleaves you at 300 ohms an-tenna - feed - impedance,but that happens to be a
value fairly easily dealtwith, using commonlyavailable 300 ohm to 75ohm matching transform-ers.
Actual ly there are probably a dozennrore "nratching schemes"; names l ikethe onrega match, the hairpin match,the beta match, del ta matching,<luarter-witve transformers, bird-cagedipoles, nratching stubs, and bazookasitre conrnronly found in antenna systemdesign l i terature. Al l have appl icat ionsin special ized antennas but are notconrnronl.y l 'ound in CATV antenna de-signs, for reasons to be discussed.
Any malching scheme is merely ant--lcctrical approach to what is basicallyrLntechrui ,cnlproblem. When we have a7l l ohm circui t in an ampl i f ier lookinginlo a 200 300 ohms circui t in a fol low-ing stage, we grab a torroid coi l , winda few turns and create a transformer.' fh is is not always the best mechanicale,n.s 'u)er ' lor the antenna, because of theproblems associated with maintainingantcnna performance in al l manner ofice and moisture loadins. So antennadt 's ignt ' rs mrrst work l t rouncl Lhe basieinrpedance and balanced/unbalanced"problem" whi le searching for a solu-t ion lhat wi l l hold up in foul weather.
Anv individual doing his own "anten-
na playing" has about al l that he needsto experiment i f he has a relat ive sig-nal level instrument (SLM/FSM) and aconstant signal source ( i .e. l ine-of-sightTV transmiLter). Simply tune for mar!
MuLti-Elem,ent Arraus
Unfortunately for us, a dipole anten-na is seldom ( i f ever) suff ic ient antennas.ystem for our needs. We usually need(1) more gain, and, (2) greater direct iv-i ty than a simple dipole antenna.
The dipole antenna has such lou;.clainLhat a good portion of the antennaindustry utilizes it as a reference. An-tenna literature which snecs model"XYZ" f tn tenna go in as td .3 db " to a
aI
II
\
I
l ^I
CATJ for
R E F L E C T O R
T
\ -- -- - ' t
DIAGRAM 9
antenna achieves most of its front-to-back rutio from the presence of one ormore reflector elements in the field ofan antenna. The addit ion of the direc-tor, on the other hand, sharpens theJ-orutard, pattern (i.e. through the direc'tor Lo the dipole element) through aneffect sim.iktr tct fctcusing. This processreshapes the receiving pattern of thedipole in the direction through the di're{:t{tr, but leaves the receiving pat-tern essentially unchanged throughthe rear (i.e. directly to the dipol.e ele-ment without passing through anyother element).
The addition of a reflector, or a di-rector, to the basic dipol,e antenna ele-ment is virtually guaranteed Lo louterthe real-life 'impedance of the dipole.How much the impedance of the dipoleis lowered depends to a large extent on
-_jTi_\'DIPOLE
I/ '
. . - . ---- . | . -t l / '
0 .05
E L E M E N T S P A C I N G W A V E L E N G T H
1 .15 .2 .25 .3 .35 .4
LOADRESISTANCE = /
./
T A B L E 3
the distance between elements oramount of coupl ing between the twoelements (whether the second, or para-sitic, element is a reflector or a direc-tor ) .
The addition of a director or reflec-tor is also guaranteed to have an effecton the length of the dipole element(and vice-versa, al though we wi l l ig-nore the effect on the parasitic ele-ments for now).
Consequently, the add,ition of euenone parasitic element into the field of adipole antenna becomes a compl icated,inter-related kind of cause-and-effectsituation. And all of the parameterschange each time you "play" with the(1) spacing between the two elements,(2) length of any single element. Infact, the addition of metal into the fieldof a parasitic antenna (or log/activeantenna) and associated effects is notconfined to the immedinte plane of theantenna, if you are looking for (or seek-ing to avoid) cause-and-effect relation-ships. A well-honed channel 4 antennasystem, for erample, joined on thetower by a channel 2 antenna array caneasily cause considerable changes inthe previously monitored and mea-sured channel 4 array performance;simply by placing the channel2 arrayabove or below (but stil l within thefield. ol the) channel 4 array.
/ t l/ l lt €
t - lt l
D I P O L E P L U SD I R E C T O R
+ 1 0
;F0 n
c
a - 5o
r l 0
;1 r s-
20
I
100 o
802;z
6 0 9F
o o Q
20
Ij
126
. - GAIN OVER
DIAGRAM 9_A
CATJ for
G A I N O V E RD I r c L E
E L E M E N T S P A C I N G W A V E L E N G T H0 . 0 5 . t . 1 5 . 2 . 2 5 . 3 . 3 5 4 point (or area if not a clearly defined
point) where for CATV purposes tbenumber of in-line elnments on a singleboom (stack) may result in less addedperformance than the additionalweight, wind surface area and mount-ing difficulties can justify. Experimen-talVHF and UHF communicatlon yagi-type antennas may have as many as B0elements on a single boom; few CATVyagl- type anto. nas venture beyondlen elements per boom. We wi l i ex-plore why this is so next month.
As you move beyond the second ele-ment (whether reflector or directorwas the second element added). theusual practice is to end up with oneeuch reflector, dipole, and directorwith a three-element parasi t ic array.
The addition of the first parasitice lement i s usua l ly fo r (1 ) inc reasedl'ront to-back ratio (add a reflector). in-creased gain (add either a reflector ora director-both end up about thesame) or increased forward patternsharpness/selectivity (add a diiector).In any case, the addition of the secondelement is usual ly calculated for opt i -mum perlormance in the desired aiea.wh ich may be in ju r ious to ob ta in ing a
LOADR E S I S T A N C E l l
t lI +
l f -t l
D IPOLE PLUSR E F L E C T O F
r o o I
ze o 9
F
Io
4 0 <
20
2 5
T A B L E 4
Tables 3 and 4 and 5 indic: ,r te whathappens to one part icular form of two-element antenna (parameters) whenthe extra element (sel f resonant para-si t ic) is a director, or ref lector; and i fthe spacing between the dipole ele-mcnt is var ied with respect to the new-lv added parasi t ic element. I t is nowonder that basic antenna design iso l ' len cons idered to he a b lack mag iclurt l
Thrt:e Elem,ent Arru..u
Most of the mo.ior chunges in thedipole characteristics t;rke place withthe r rdd i l ion o l ' the / i rs1 paros i l i c e le -mcnt . Whi ih i s ano iher way o f say ingthat after the first bite, the additionalbi tes have less and less effect on thebasic array as tuned to that point. St i l l ,even with very long experimentalyagi arrays of 10 or more elements, thedes igner cont inues to exper ience com-plex re-tuning procedures each t ime hedecides to expand the array l:y a singteadiitionol element.
Naturally it is wise to determinewhy you would want to continue toincrease the size of an array. Basically,you are trying to increase the capturearea of the antenna, which is anotherway of saying "add gain." There is a
J U N E , 1 9 7 5
P .oo
d
o
o
E .oo
q
4s l0^
.05 .1 . r5 20 25
DIPOLE TO FEFLECTOR SPACING WAVEL€NGIH
A t h r e e e l e m e n t y a g i t y p e a n t e n n a , w i t h a d j u s t a b l er e f l e c t o r t o d i p o l e s p a c i n g ( b o t t o m l i n e o f c h a r t )a n d a d j u s t a b l e d i r e c t o r t e n g t h ( t e f t h a n d e d g e o ic h a r t ) o n a b o o m 0 . 3 w a v e l e n g t h s l o n g w i l l p r o d u c ea 7 O ( 7 5 ) o h m d i p o l e f e e d i m p e d a n c e w h e n t h e r e -f l e c t o r t o d i p o l e s p a c i n g i s a p p r o x i m a t e l y 0 . 2 1w a v e l e n g t h s , a n d t h e d i p o l e t o d i r e c t o r s p a c i n q i sO . O 9 w a v e l e n g t h s ; w i t h a d i r e c t o r l e n g t h o f O : 4 2w a v e l e n g t h s .
l-
TABLE 5
27
U
zo
=o
FzE
;o6
E L E M E N T S P A C I N G W A V E L E N G T H
. 0 5 . 1 0 . 1 5 . 2 0 . 2 5 . 3 0 ings eibher side of the dipole element of0.15 and 0.20 wavelengths. Obviouslymatching to a 75 ohm transmission l:tneis compLicatecl by the addition of angsirtcluktr extra eLement.
I lowever, when the antenna hasa ref lector, dipole, and director, thereare spacing combinat ions where thedipole impedance can actual ly bebrought back very close to 70 ohms(see Table 5). This is not to say thatachieving a 70'75 ohm dipole feed im-pedirnce is the onl'u utnsiderution wemust be concerned with; frankly, ftmtu lte the eusiest to r:rrrect with an-lennit "pruning" etf ter we haveachieved the desired (1) front- to-backrat io, (2) l ' ront- to side rat io, (3) gain,(4) control of minor antenna lobes.St i l l , iL i l lustrates that i / you thouoht't1o'u hrul, u, lur,n,dJ:ul oJ utrrfuiltles to pknl'uri.th., uti,l h o. tu;o-element antenna,your var iablcs iust increased by 2X-3Xwhen you added the third element!And irn.y one of these variables canspel l disaster, or success, for the de-sisncr who knows how to make themal l plav to his advantage when he is outto solve a part icular receiving prob-t cn t .
Next month we shal l discuss beam-widths, bandwidths and pract ical an-tenna construct ion pract ices.
7 d B
6 ir8
I5 0 i
IiI D I P O L E /
I - o t R e C t O n/ G A I N
7 0 ;
s o t
5 d B
4 d a
3 d B
2 d B
l d B
0 d B
6z
oz
il'ii:bj'")')F e e d l m p e d a n c e a t c e n t e r o f d i p o l e e l e m e n t , f o rt w o e l e m e n t Y a g i - U d a , a s a f u n c t i o n o f i n t e r - e l e -m e n t s p a c i n g s , A l s o s h o w n i s g a i n o f d i p o l e p l u se i t h e r r e f l e c t o r o r d i r e c t o r , a s f u n c t i o n o f i n t e r -e l e m e n t s p a c i n g .
CHART 3
good match lrom the two-element an-tcnnir to tlr,e trrm,smission l:ine. For example, zrs shown in Chart 3, the opt i-mum gain for a two element antennawith director is achieved when the di-rcctor is between 0.1 and 0.15 wave-length in front of the dipole element.And opl imum gain for a two-elementanlenna with ref lector is achievedwhen the ref lector is 0.15 to 0.2 wave-lengths behind the dipole element.However, the impedance of the dipoleelement, as shown in Chart 3, witheither director or reflector added, hov-ers between 20 and 42 ohms for spac-
CATJ CONTEST F( )R READEBS
H o w w e l l d o y o u r e a d C A T J e a c h m o n t h ? C o u l d y o u h a n d l e a s i m p l e q u i z 0 n w h a twas conta ined in th is tssue? How wou ld you score?
W o u l d y o u l i k e t o f i n d o u t ? W e w o u l d . A n d t o m a k e t h e " g a m e " j u s t a I i t t l e m o r etan t i l i z ing , we are go ing t0 g ive away pr izes . Not your everyday hum-drum pr izese i t h e r , b u t b i g p r i z e s . T h i n g s l i k e a m p l i f i e r s , t e s t e q u i p m e n t , a n t e n n a s , p r 0 c e s s i n ge 0 u i D m e n t .
S o u n d t o o g 0 0 d t 0 b e t r u e ? W e l l k e e p y 0 u r h a t o n , y o u r p e n c i l s h a r p a n d y o u r m i n da ler t because lus t a round the corner (and down the lane) the CATJ READER C0NTESTi s l u r k i n g : r e a d y t o p o u n c e u p o n y o u r b o d y .
We are cur ren t ly c lear ing th is "scheme" w i th the Pos t 0 f f i ce au th0r i t ies (you th inkt h e F C C h a s r e d t a p e l l ! ) a n d w e e x p e c t t 0 a n n o u n c e t h e f i r s t c o n t e s t i n t h e A u g u s tissue oJ CATJ.
K e e o t h e f a i t h .
28 CATJ for
Expand Your Test Abi l i t ies
SADELCO 260-4 ANALYSTISALOTOFMACHINE
Uyt: llyyASisnol Generator
In the January CATJ, in the wrap-up port ion of our four-part ser ies onlh t ' p rcs t 'n t s l l r le o l ' the i r r t fo r SLM/I, 'SM devices, we began a review of thcStrt l t l t . , t nrodt ' l 260 A Slr t ,<. trum Anirl v s t . A t l h u t t i m t ' w t ' n o t e c l l h i r l w ewcrer pr imari ly deal ing with the refcr-cnce signul level I 'uncl ions of the 260 Aand that in the future we would revisi tthis inLerest ing piece of test equipmcnt .
' fhe luture is now. And in the inter-inr I 'ew monlhs we have had the oppor-tuniLy to work extcnsivel_y with the260 A and to tal l< with operators abouti t . Frankly, af ter using i t , and t ;r lk ingwith others about i t , we wonder whvs.ystem operators have so far manageclt o l v o i d t h e u n i t s o e x t t ' n s i v e l v . T h eI'at:ts are thert most system operatorsdo no t l rppeur to know wha l the 260 ASpectrum Analyst does, or why i tshould probably be the first piec"e oftes t e r l r r ipment they look ser ious ly a tr t l ' t t ' r uc r lu i r ing a r lua l i t y SLMzFSM.Now th i r t i s ed i to r ia l i z ing , und we rea_l i ze i t ; bu t the l 'ac ts a ie qu iLe p la ina l ' te r work ing w i th the 260 A, and wehe l ieve you w i l l lg ree a f te r read ingtnls reDorl .
One of the users of the instrument (avery wel l -known Canadian consult inggroup) uses the 260 A for checkins ouTnew {and o ld ) sec t ions o f CATV p- ian t :they use the broadband no ise ou tpu tmode { l ' l a t to w i th in + / - 0 .7 db on iheunit we received for test and review.
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ovcr the range 50 300 MHz) as a sisnalr . iorrr( ' ( ' , p lugging lhe 260-A noist ,
'out.
put into the sect ion of plant they arechccking, and then ad. just ing the re-sponso o I th i r l p lan t sec t ion an anrp l i f icr at a Linre with ei ther an SLM or :rpr l r table spectrum anal.yzer, such asl h t ' V S M l .
Another operator in Cal i fornia toldus that his underground crew carr iesthc 260 A around with them to checklor cublc faul ts in new sect ions ofplant, using the 260-,{ with an SLM tocal<:ulate where shorts or opens exist .' fh is is a procedure that involves usingI ro lh the 260 A and an SLM/FSM tonleusure the frequency di f ference be-tween standing waves on an open (orshorled) l ine, applying that f requencydi l ' l 'crence as a number to a chart sun-pl ied with the 260-.4 to ascertain thedistance from the measurement pointLo the cable faul t .
A service facility toitd CATJ thevused the 260-4. as a noise source witirtheir FSM to check noise fisures forpre-ampl i l ' iers and broadband ampl i f icrs they service.
A fel low in Oklahoma checks out an_tenna match; numerous operators wetalked to use the 260-A as a referencelevel to check calibration for the SLM/FSM units.
Yel for every person we found usingthe 260 A, we found perhaps ten oimore who were not even aware of its
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applications. Many mistake the Sadel-co phrase "Spectrum Analyst" to meanthat the unit is similar to the VSM-1spectrum analyzer (it i,s not). Othersthink it is merely a complicated SLM/FSM calibration source. One distribu-tor we talked with volunteered that hehas had three 260-4 units in stock forseveral months, and "no movement in-dicated."
Finally, we talked at Iength in NewOrleans with the 260-A's designer,Harry Sadel, and learned that he wasseriously considering removing someof the functions from the 260-4' (suchars the bridge) as at least an alternativeor option for the prospective buyer."They are selling well in South Africa,"noted Mr. Sadel, "but here they seemtoo complicated for the average sys-tem operator."
Recal l ing that television was br:rndnew in South Africa and that anyone inthe distr ibut ion business there wasbound to lack our twenty-five-year(plus) backlog of technology, i t seemedincredible to us that Sadelco mightconsider redesigning the "box" be-cause the U.S. (and Canadian) CATVmarket was having a hard time appre-ciating what a versatile test instru-ment could be purchased for under$600.
Briefly
The 260-A is a source box. It pro-duces two types of signals; one is aprecise (self-calibrating) 73.5 MHzcrystal-controlled carrier at 1,000 mi-crovolts (1 mV) Ievel. This precise lev-el is used as a reference source for bothmeter calibration alone and as a refer-ence source to adjust precisely thesecond source generated by the 260 A.The second source is a wideband noisesource: sort of an "everyplace at once"slDeep kind of signal. Noise is an excel-lent reference tool, if you know (1) theexact level of the noise, and, (2) if thenoise is spread out in frequency so that
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S A D E L C O 2 6 0 - A S p e c t r u m A n a l y s t h a s s e l f c a l i -b r a t i n q C W c a r r i e r m o d e a n d w i d e b a n d n o i s e m o d e ;b a t t e r y c h a r g i n g s y s t e m -
it covers all of the frequency rang(,'that interests you. That is basical lywhat the 260-A wideband noise sourceis; u precise leuel noise source that ex-tcnds from 4.5 MIIz to 300 MHz, withincredible flatness (Sadelco says t/-0.25 db over the range; in the 50-300MHz ra,nge we were most interestedin, we found */- 0.1 db f latness to bethe case).
A sweep signal has about the samecharacter ist ics for many appl icat ions,except the sweep source requires ascope for accurate display, and it is notreally spread all across the spectrumconstantly; rather it "sweeps throughthe spectrum" at some pre-determinedrate. A sweep display system dependsupon the persistence of the phosphorof the CRT display tube to make itepf)eor that it is all across the desiredspectrum at the same time. A wide-band noise source simply is euery plnceQ,t OnCe.
A sweep signal, even from the newWavetek 1050. requires a little ingenu-ity to move around quickly any place inthe plant. The 260-4., operating fromits own internal rechargeable batterysource, goes with you any place thatyou require a wideband signal to pluginto a section of plant.
The 260-4 will:(1) Calibrate field strength/signal
level meters;
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(21 Measure ampl i f ier gain, passiveloss and act ive or- passiue re_sponse curves with a conven_t ional SLM/FSM as a read_outtool;
(3) Generate the aforementionedwideband noise source for am_plifier tilt and gain checkout,again with an FSM/SLM as aread-out tool:
(4) Measure return loss and al lowyou to calculate VSWR with thesame SLM/FSM as a read_outdevice;
(5) Determine the location of cableopens or shorts, from as muchas 500 feet of cable awav:
(6) Measure the noise figure ofbroadband or single_-channelamplifiers, again with the indis_pensable assist of a SLM/FSM;
(7\ Provide a erystal-control led sis-nal source of TB.5 MHz (otheisare available if ZB.b MHz both_ers you) to plug in at the head_end for checking your systemradiation compliance for innualFCC tests.
. Tlat, briefly, is uthat the 260_A cand0 Jor Aou.
Substitute For Staeep?
invest ing in (1) a sweep, (2) detector,and (3), a scope.We talked about this in the Mav CATJ(see Wauetek 1050 Review, page 31,Muv) '
A fairly powerful argument could bemade for the'260-4 in the same vein. Inpractical use, the 260-A calibratedwideband noise source can do many ofthe things which the sweep generitorcan do. The detector and scope youneed with a scope are already on hand,in your FSM/SLM. Now it
-should be
noted that a sweep, detector, andscope u' i l / let you sec ond detect l l t inosthal you connol see and delect with a260 A, and the pr imary reason for thisis the 1imilo tions of the SLM/FSM as aread-out device. Close (t ight tolerance)work, such as measuring the preciserate of roll-off of a bandpass filter, forexample, is 6;oing to be a lot cleaner,r ;uieker, and perhaps more accuratewlt f a sweep, detector and scope thanwith a 260-.4 and FSM/SLM. Thebroad (relatively speaking) i.f. re_sponse o f the SLM/FSM is the cu ln r i there: i t I imiLs the . ,def ini t ion. '
.you canmeasure accurately wi lh the 260_4 as awidehand signal souree.
So there ii a trad,e-off in the mind ofanyone considering the usefulness ofthe 260 A versus Lhe l im i ta t ions : and
Maly of these functions possiblysound suspiciously l ike the "r tru -"o_surement assists you get when you ex_pand your own system's test equip_ment to include a wideband sweep testse l un .
Although we have never discussedthis with Harry Sadel, we suspect that' the same thoughts occurred to hi-dur ing the course of his developmentperiod for the 260 A. On the ariu-p_
.. !i_o1_that you already have an FSM/SLM in your shop, and on the pre-sumption that you find situationswhere.the signal or field strength me_ter is just not enough test equ-ipmentto maintain your plant properlv. vou
, probably have given some ft ougi to
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T y p i c a l V H F n o i s e g e n e r a t o r . J a c k s J 1 , J 2 a l l o wm e a s u r e m e n t o f d i o d e c u r r e n t ( 2 m A m a x t y p l c a l _l y ) . M o u n t 7 5 o h m l o a d r e s i s t o i d i r e c i l y t " 6 r i p u tj a _ c k w i t h v e r y s h o r t l e a d s . M o u n t n o i i e d i o d e t o7 5 . o h m l o a d r e s i s t o r w i t h v e r y s n o r t l e a d s , a n Jb u t t o n ( m i c a ) 5 0 O p F i s a t s o m o u n t e d w i t h v e r ys h o r t l e a d s . t N 3 4 d i o d e n o t s a t i s f a c t o r y f o r V H iu se .
It
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500pfBUTTON
DIAGRAM 1
3 1
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the expense of adding the 260-4 versusthe expense of adding whatever com-ponents you need to be in the sweepbus iness .
As a Wide Bund So'ut'ce
Many of the straightforward applica-tions of the 260-4, revolve around theol ' t -mentioned wideband noise source.In the simplest form of noise genera-tor, a diode is made to draw current,and it therefore creates noise. Thenoise generated by a "diode drawingcurrent" is in the main l imited by thecircui try employed with the diode. Asampl,e (not 260-A) wideband noisesource schematic is shown in Diagram1 .
A diode drawing current emits control lable amounts of noise, over a con-trol lable spectrum width, through cir-cui t t r icks, the f latness of the wideband noise generating diode circuit canbe held to very t ight tolerances. Thelevel of the noise can be controlled bycontrol l ing the amount of currentdrawn by the diode. Or, the diode canrun wide open at a fixed current, andthe actual output level of the noisesource can be step attenuated in 1 dBsteps with precision step attenuators.
The 260 A has a maximum widebandnoise output of *10 dBmV (for a .5MHz SLM i . f . bandwidth): this is con-trol led down to -10 dBmV in 1 dBsteps with the front-panel step attenu-ators. For most applications, a wide-band level of *10 dBmV would be ade-quate. For those special circumstanceswhere it is not, the noise can be fedinto a post amplifier to achieve addi-tional level (amplification) to whatever
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level is desired and the post amplifi-er(s) can handle. It should be notedthat if you are going to use the 260 Afor line amplifier balancing, the *10dBmV is in the right ball park for manyamplifier recommended inputs.
Calibration (if exact level calibrationof the wideband source is required) ishandled by switching the 260-4 to thenarrow-band (CW) position. Here itproduces a self-calibrated (+/- 0.25dB) 73.5 MHz carrier which is util izedwith the aid of your SLM/FSM to cali-brate to a 0 dBmV reference level.From here it is simply a matter of slid-ins attenuation out of the slide attenu-ators to reach the desired level (up to*10 dBmV or down to -10 dBmV).
Diagram 2 indicates how the 260-4plus SLM/FSM is connected to cali-brate the signal level meter. Measur-ing gain, loss, and response is shown inDiagram 3. The procedure for Diagram3 is almost the same in each case.
(1) The wideband source ischecked for its own level, asread out by the SLM/FSM;
(2) The wideband source is thenfed into the device under test,and the SLM/FSM connectedto the output port of that de-vice:
(3) I f you are measuring gain (am-plifier) or loss (filter, DT, split-ter, etc.) , s imply note the di f fer-ence in reading between the260 A direct to the SLM/FSMand the reading through the de-vice under test. If the device isfrequency sensitive (i.e. selec-t ive), s imply tune the SLM/FSM either side of the device'sdesign frequency and, note thedifference in readings. You canplot this on a piece of graph pa-per to compose a quick and sim-ple chart of the "response
curve" of the device being"swept" with the 260-,{ and theSLM/FSM.
sLtvl / FSM
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(4) If the device under test has abuilt-in tilt, the wid,eband, flntoutput of the 260 A fed into thedevice will allow you to quicklyverify the true tilt of the de-vice. Simply jot down the SLMreadings made through the un-der-test device as you "sweep"
the SLM/FSM from 50 to 220MHz (or over whatever range isof interest) and jot down-thelevels. Transpose these to apiece of linear graph paperfound at the corner drug itore,and you have a visual presenta-t ion of the device response.
The same procedure will work forpre checking out rol ls of cable; drop orplant. Simply feed the 260-.4 into oneend of the reel and connect the SLM/FSM to a connector on the oppositeend. PloL the readings on a piece ofgraph paper. Because the output of the260 A is flat, any deviations from a flatoutput as read through the rol l of cableare due to cable tilt (roll-off) as fre-quency increases, or dips and val leysare due Lo co,bl.e continuitg problems.Better to f ind out at the shop thanal'ter installing 2,000 feet of the stuff!
Arul A Britlqe
In a transmission system at VHF(i.e. trrtnsmitter loading into a trans-mission, Line connected to an antenna\.lhe eJf ic ienc4 of the Lransmission l ineancl antenna are commonly determinedby insert ing into the transmission l inea device known as a "bridge." A bridgeis an instrument that (usually) me-asures the amount of transmittei powerflowingfrom the transmitter to tie an-tenna, and also measures the amount(or pereenlage) of power not acceptedby the ontenno, and returned baek Lothe transmitter. The returned, pouer iscalled standing u)eues, the analogy be-ing that "waves" (or power) not atcep-ted by the antenna and radiated infothe atmosphere "stand" upon the
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ara'raa, I o3
*o...o,..OMilil), R E S P O N S E
DIAGRAM 3
t ransmission l ine. Of course theu dor t t t l . s l t rnd any p la< .e ; they are mou ingwith the speed of l ight ( less the slow-down factor of the dielectric constantof the cable), and they in fact end upprimarily back in the transmitter pow-er ampl i f ier, where they cause addi-l ional heaLing of the ampl i f ier stage.
The pract ice of measuring [her rn rount o f power re tu rned by the"load" on a transmitter has developedinto something called VSWR measllre-ments; or measurement real ly of theefl' iciency of the transmission line/an-tennu system in communicat ion svs-tems. This is olten expressed ur u p"u"-centage, and we have simi lar ly adop-ted the practice in CATV by referringto match (i.e. impedance match be--lween two separate component parts)as so many dB. We commonly note thatthis or that box has a 20 d.B match.wh ich is s imp ly another way o f say ingthat according to VSWR measu"emenTcri ter ia, the amount of power ref l ,e 'ctedor retuntecl from the "load" at the endof our transmission line (or the input oroutput port of the device we are mea_suring) is 20 dB lower ( i .e. less) thanthe leve l o f power wh ich is sent in tothe device or line. In real life, a 20 dBmatch is the same thing to us as aVSWR of 1.22 is to a coirmunicat ionsperson. Both mean the same thing.
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33
tittt
DIAGRAM 4
Both also mean that in terms of powerinitiated, 4.4olo of that power is re-flected away (i.e. not accepted) by thedevice which has a 20 dB match/VSWR ol 7.22. These are not magicnumbers that require extensive matchbackground to calculate or formulate;charts abound which spel l out al l ofthis and more, and i f you know (forexample) that the match is 20 dB, thecharts quickly al low you to determinewhat the equivalent VSWR is and theequivalent percentage of power not ac-cepted by the load or l ine.
Match or impedance matching be-tween two separate devices or com-ponents is one of the important factorsthat all CATV people must learn tocontend with. In a nutshell, the "better
the match" the more efficient thetransfer of input power going into adevice (any device, including transmis-sion cable) and therefore the more in-put power that actually goes into thedevice. Every CATV component hasmatch (input and output) criteria. Apre-amplifier on the tower with a 10 dBinput match wi l l lose ( i .e. not even ad-mit) approximately 30o/o of the anten-na-delivere d signal uoltage to the inputof the pre-amp, for example. Anotherdevice, with a 30 dB "match," will ef-fectively lose just over 3o/o of the deliv-ered signaL uoltage at the input to thedevice.
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Obviously, we are nof anxious togive away ualuable pouer (signal volt-age) any plnce in a CATV system. Andevery conductor, every splice, everyinput and output port, even every footof cable, if it has a "poor match," givesaway power (signal voltage).
There is one more reason to be con-cerned about match: that is the previ-ously referenced "standing waves."Again, the waves don't stand anyplace, they move about very rapidly.But along a specific length of cable(where waves are said to "stand") theyappear to stand stil l. That is, theg haueuoltage and current martmums andminimums along a specific piece of ca-ble (the amplitude of these voltage andcurrent peaks and nulls is directly re-lated to the VSWR); simply becausethe standing waves appear to alwaysbe current or voltage peaking at thesame po'int along the specific (unchang-ing) lenglth of cable. These "standing
waves" are signal components that didnot make it into the normal forwardflow of signal. In effect, they are out of.the "mainstream" of travel, becausesome device (connector, etc.) has said,"No, 3o/o of you guys have to stay outof my connector innards (match of 30dB referenced)." Now when you plugthis l ine, with a standing wave on i t ,into something like a teleuision receiu-er, the receiver sees not only the for-ward-flowing wave (the 97olo of thepower that is accepted), i t ako sees(weakly, or less strong than the 97oloforward-flow signal) the standing'tDCLues. These "delayed-in-time" sig-nals, as displayed on the television re-ceiver, show up as slight ringing (orghosts) on the picture tube.
So not only are we concerned withmatch and standing waves becauseprecious power can be lost (power losttranslates into decreased amplifierspacings, which translates into morebucks per mile of CATV plant), we areconcerned because our customers lookat their $800 color receiver connected
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to our cable and say, "What are thosefunny, faint lines outlining the man'sface just to the right of his face?" Andthat translates into unhappy custo-mers, which translates into bucks lost.
All of which leads up to the need forat least one system-available methodfor checking component match. The260 A will let you do this, with theassistance of the omnipresent SLM/FSM. Sce D iagram 4 .
In use, the 260-A uses the SLM/FSM to read forward-going power (asa relerence), and using somethingcal led a br idge (the device that detectsreturned power present in the form ofstanding waves) the SLM/FSM thenmeasures the returned power. I f youstart out with a 0 dBmV reference sig-nal (wideband noise from the 260 A)and find that in the retunted-powermeasurement mode you have _20dBmV level present, you match is 0minus 20 or 20 dB. That i s a l l there isto i t ! I f you want to change this topercentage of transmission loss orVSWR, a handy chart with the 260-,{does i t for you. The process is quickand simple and can be appl ied to anyact ive device ( to check input or outpuiport match), any DT (to check input,output ports or tap ports), any passivedevice such as a spl i t ter, bandpass f i l -ters (you may discover somethineher t ' ! ) . o r a ro l l o f cab le .
By using the wideband noise source(flat from 50 300 as noted) to check arol l of cable you can measure lhe ca-bLe's actual loss, tilted as it will be.from 50 300 MHz, and Lhen turn theprocess around with one simple con-nection change on the 260-A and mea-sure the match of the roll of cabl.e. Todo both on a roll of cable where youhave access to both ends of the cibleshould take you about two minuteslonger than it takes to put the connec-tors on. That is a fair investment forspotting cable problems before youhave spent hours installing that rbll!
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An open line (no termination) or ashorted l ine (crushed cable, etc.)would, as you might suspect, havethose nasty standing waves sittingaround, if RF power is applied into oneend. After all, with an open or short.the l ine is not terminated in Z5 ohmsany longer, and when the inward-bound signal runs into that non-25-ohmter.mination (or open), it is going tore.iect some portion of the inward-bound signal and set up standingwaves.
The 260-A, again with the able assisto{ an SLM/FSM, can help you locatethe area along the cable where theopen or short is located. To v'erify thatyou have a short or open, simply iollowthe out l ine for checking on match (seeDiagram 4). Once veri f ied, you can usethc 260-4. to pin down where along thel ine the short or open should nc, wit t rprettv decent accuracy, in about 500leet of cable. This means that you canactual ly handle 1,000 complete feet ofcah le in a s ing le span by 'go ing a t i tfrom both ends.
The pr inciple is this. I f there is ashort or open, there are standingwaves. Standing waves are frequencycoherent; that is, they set up or standup (if you will) at precise points alongthe cable medium based upon the dis-tance between the transmitter source(the 260-.4) and the short or open. This"precise distance between standingwave peaks" (vol tage peaks) is alwayia function of the distance betweensource and fault. And you can readthese peak-and-valley voltages by tun-ing an SLM/FSM through a relativelynarrow range (usually within a TVchannel span or two) and note on yourSLM/FSM the frequency on the dialwhere these voltage peaks appear. TheMHz difference betuteen peaks tellsgou something: it tells you the distanceto the short or open, if you happen toknow the dielectric constant ofihe ca-
Opens and Shorts
35
DIAGRAM 5
ble. The 260-4 gives you a chart forthis that tells you, for example, that ifyou find you have 10 MHz betweenvoltage peaks as tuned on your SLM/FSM, that the short or open is 31 feetaway from you in polyethelene foamcable. I f you happen to have a spl icedown the line 31 feet, you know uthereto start your search for trouble!
This is done with the 260-4. an SLM/FSM, and simple-to-read chart orgraphs. I t is, in a sense, a poor man'sTDR.Noise I'io'ure
Most people think measuring noisefigures is a back-room black art. Thefact is that with a wideband noisesource such as the 260-A. an SLM/FSM and reasonable intel l igence youcan not only measure (and spec) anybroadband or narrow-band ( i .e. s inglechannel) ampl i f ier noise f igure with re-spectable accuracy, you can do i t withrepet i t ion and have correlat ive results.
Why bother, you ask. Let 's take sin-gle-channel pre-ampl i f iers. They si t upthere 200'600 feet above ground andperk away for years. But you have thegnawing feel ing that the signal- to-noise ratio "looked better" two yearsago when you put the unit into the air .Maybe some moisture has gotten intothe unit ; perhaps a ser ies of l ightningstr ikes on your tower has slowly cre-mated the input F f i t t ing on the unitand i t s imply no longer has a decentmatch (which means antenna energy isbeing reiected, which means signal- to-noise has suffered). You could take theunit down and replace it with a newone. You could take it down and look
36
for cremated parts, signs of moisture,and what have you. Or you could takeit down and check the gain, responsecurve, and noise figure (oll with the260 A and an SLM/FSM).
In the noise figure game there arenumbers, and then there are numbers.Any supplier that produces noise-fig-ure-sensit ive units ( i .e. pre-amps, pro-cessors, etc.) has a spec on his datasheet (or even imprinted on the uniti tsel f , such as many pre-amps now do).The chances of your taking your 260-.4and SLM/FSM and measurins theno is t ' f igure o f your un i t (even i f b randnew right out of the box) and matchingl.he imprinted on the unit-noise-figurefrom the supplier are slim at best. Youmay measure higher, or you may mea-sure lower. But you will sekl,om, ifever, mealure the same.
This is not to say that the supplierhas cribbed on you. His noise-figuretest setup is probably considerably dif-ferent (read elaborate) than vour260 A and SLM/FSM. He -"oru.".precise noise figures, on his test setup,al lday long f ive or six days a week. Hisnumbers are his numbers, and whilethey may (or may not) have sometraceability to real world noise figures,they are in truth relntiue more thanprecise.
So too will yours be with the 260-,{.If you start out with a neto pre-amp (orprocessor) and measure noise figurebefore installing the unit, record themeasurement you make for later refer-ence, and then check back on the unitone, two, or three years hence to seehow it is doing; then your originalnumber means something, providedyou are stil l using the 260-A and thesame SLM/FSM for the subsequentcheck .
Or you can reference the unit youpulled off of the tower against anotheridentical, spare (not necessarily samechannel, but i t should be the sameband such as low or high) type of unit.If the tower unit is considerably higher
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in indicated noise figure than thespare, suspect that you do have a prob-lem.
Summaru
The 260-A does so many things thatit is hard to find fault with it. Rather, itis our studied view that if there is faultto be found, it is with an industry thatruns around crying and screamingabout plant problems or supplier-de-fective equipment which could be spot-ted and corrected quickly and aciur-ately for not very many test-equip-ment bucks, with the 260-'{.
If there is fault to be found withSadelco for the 260-.4, it is the manual.The manual is al:rnost too comprehen-si.z,e for the average CATV system op-eratcir. The instrument itself is easu tooperot.e and simpl,e to und.erstand.. )hemanual makes long, lengthy cases forthe use of higher-math equations forsimple things l ike locat ing where ashort or open is, or how to measurenoise figure. The material presented isclose to flawless, but the approach is.scorzl because the average CATV typewho takes the t ime to look at the man-ual before buying the instrument will,we feel, come away shaking his headand mutter ing that he never got be-yond tenth-grade algebra (and most ofthat he has forgotten!) .
Yau tlon't need any m,ath to operatethe 260-A. The manual, whi le being ex-haust ive to the point of losing every-one but Archer Taylor or SrukiSwitzer, ends up most of the explana-tions with a table or chart that anuonewho ean draw a s t ra igh t l ine w i th " theaid of a ruler can comprehend and use.
In short, don't be scared au;au bu theSadelco passion for long, d,etdited,hiq hLu mathematical explnnations. Ona pole, in a ditch or even on the towerwith you and your trusted SLM/FSM,the 260-4 will provide instant and sig-nificant measurement results for eventhe novice.
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Sadelco 260-4 Specifications
Wideband GeneratorA) White noiseB) 4.5-300 MHzC) Min output *10 dBmVD) Flatness +/- 0.25 dB
Narrow-Band GeneratorA) 73.5 MHz crystalB) Output level 1 mVC) Accuracy +/- 0.25 dBD) 75 ohms, VSWR 1:1E) Harmonic levels, -35 dB
Return Loss BridgeA) 75 ohms impedanceB) Ba lance -40 dB minC) Unterminated ref level -1 mVD) Flatness +/- Z dBE) Open,/short rat io 1 dB or better
AttenuatorA) 1 each 1, 3, 6, 10 dBB) continuous +/- 1 dB
Operating TempA) +60/+85 degrees F, negl igible
variat ionfl) +32/ +I00 degrees F, +/- 0.5
dIl varial,ion
BatteryA) 13 Eveready CH500T or equalB) 6 hours on charge, widebandC) 36 hours on charge, narrow
bandl)) 10 hours charging t ime
PhysicalA) 4-3/8 x 81/z x 11 inchesB) 9 pounds with caseC) Price - $595.00D) Manufacturer:
Sadelco, Inc.299 Park Ave.,Weehawken, N.J. 0?08?(20r/866 0912)
37
Even Small Systems
Today nearly every cable system inthe country is faced with a lack offunds. There are as many causes asthere are systems, but some of the ma-jn. contributions are inflation, in-creased technical reouirements. soar-ing in te res t ra les and the inereases inlabor expense with the cost of l iv ing.Rates which were f ine in 1967 simnlvwon't pa.y the bi l ls today.
Asking for a rate increase is a lastresort. First, a system owner or manager must make sure that he is makingthe hes t use o [ ever .y do l la r he has andthat he explores every option availa-blc. This takes time and effort, and inmany cases an accountant 's know-ledge.
Up unt i l now I 've made al l too manydecisions on a "gut feeling" or "experi-
encc." This wasn't by choice; i t s implytook too much time to prepare a com-plete projection. I think I was rightmore often than not, but then I'mlucky.
One way to get the information thatyou need is to make a complete finan-cial projection for each option. This canbe done quickly and easily by letting acomputer handle most of the time-con-suming, tedious jobs. The system man-ager is then free to explore which op-tion should be followed, and to makedecisions based on the best projection.
Basically, there are only two waysprofitability can be improved. You canreduce expenses or you can increaserevenue. That sounds simple, some-
COMPUTER TECHNOLOGYAIDS RATE INCREASE
PRESENTATIONS"Mr. Mayor, members of the ci ty
counci l , ladies and gent lemen. Mvname is John Turner, and as you know,I 'm the Manager of the cable system.We need a rate increase.We've been charging our customersthe same rate for seven years and iustplain can' t l ive on $4.95 a month. Wewere thinking about rais ing the rate to$5.95 a month and increasing the in,stallation fee from $15 to $25. I hope toput the new rates into effect June 1stand wi l l answer any quest ions you mayhave. "
At that point he was interrupted byshouts from the audience. I t seemedthat everyone there knew more aboutthe financial status of cable than thesystem manager. The Citizens Lobbgfor Pubkc Access wanted a televisionstudio with color capability and staffmade available. The Leaque AgainstViolence wanted fewer murders andmore football. The Decencu in Medingroup wanted less sex and more soapoperas. They all wanted the rates re-duced and a new franchise hearing,with competitive bids and minorityparticipation.
This is a scene many of us will faceover the next few years. It's not pleas-ant, but it can be productive.
oa:James A. RichardsonPLANTATION CABLE/RESEARCHo/o Plantation Cablevision. Inc.One Park DriveHilton Head Island, SC. 29928
3B CATJ for
thing everyone knows, but how you dothat is a little more difficult.
Running a cable television system ispu-ch like trying to maintain an ecolog-ical balance. You can't make changes ina vacuum. Everything you do must berelated to its middle- and long-term ef-fecL.
First, consider how a computermight be used to help reduce expenses.In most systems the largest singleitem is debt service. Debt service itselfdepends on just about every action youcan take. In addition to the obviousone, revenue available, there are otherimportnnt but subtle factors.
Of major importance is how muchplant you build, and when you build it.By rescheduling construction, it is of-ten possible to improve the overall pic-ture. Reschedul ing is not without haz-ards however. You will lose the rev-enue from whatever subscriber youwould have hooked up in the delayedarea. You will also increase the cost oflhe plant by whatever effect inflationhas on the cost of labor and materials.Changing the amount of plant youbuild in a given period will also affectyour operat ing expenses, the numberof techs and instal lers required, taxes,and insurance and franchise fees.
Ry hand, this would be a major job.With a computer you simply changetwo input l ines, mi les of plant bui l t peryear, and additional homes passed.The machine wi l l then handle al l thecalculations; you look at the resultsand pick the most promising.
Another major factor in debt servic-ing is the loan itself. Over the pastyear, interest has increased over sixpercent. Now it is beginning to decline.!i-p]V refinancing a loan might help.For those ofyou who have a loan basedon prime rates, it is essential that youknow what effect changes in the p.i-erate have on your system's cash-flowposition.
If your system was financed at ahigher interest rate it might be profit-
J U N E , 1 9 7 5
able to explore refinancing. If interesthas come down, you could save thou-sands of dollars. A drop of only onepercent on a $150,000 note would mean$1,500 a year to your system. If yourloan is larger or if you can refinance atmore than a percent less than you arepaying now, you could save even more.The computer lets you find the overalleffect on your system quickly and pain-lessly.
As expenses increase and sources ofmoney become scarcer, new forms offunding must be explored. Leasing isone of them.
Leases come in many types. Beforeanyone decides to lease a system, heshould thoroughly explore the effectson his system. Who takes deprecia-tion? Is there a set purchase price forthe system at the end of the lease?What about maintenance and replace-ment of plant? Who pays taxes andinsurance? All of these factors may besimulated with a financial planner. you
Computers? Good Grief!
Author Richardson proposes thatCATV systems and systems-to-beequip themselves with sufficient factsand figures to be able to make a co-herent presentation to (1) ci ty counci ls,(2) lending inst i tut ions, when the needarises. One way to have the data avail-able is to laboriously compute it all byhand.
Richardson, mindful of the growinguse of computer technology in allphases of business, urges system oper-ators to consider how much quicker,nicer, and more accurate computer-comparison studies can be. He doesn'tindicate at what system size such ap-proaches become too expensive for con-sideration, but he assures CATJ thatLhe program he has written has beenextensively used in the development oflhe P lan ta t ion Cab lev is ion sys lem a lHil ton Head Island (1150 subs at ores-en t ) . The program i tse l f i s wr i l ten andavailable, and we review its functionsseparately here.
f39
can compare a lease, lease-purchase, orconventional financing package beforeyou decide.
So far we have only talked aboutdebt service as a rvay to reduce ex-penses. There are other factors whichshould be investigated. Fortunately, acomputer model lets you try ideasquickly. Are there any items whichwould significantly affect your profit-and-loss position? How large an inven-tory are you maintaining? Often peopleare amazed when they stop and add upthe dollars in their storeroom and ontheir trucks. How about your over-head? Are there any places where youcan cut costs without harming service?A computer can't give you the an-swers, but it can certainly help yougather the information to make achoice.
The other way to improve your fi-nancial position is to increase your rev-enues. You can do that by increasingyour number of subscribers, or by in-creasing your rates.
You can increase your subscribersby selling more people or by buildingmore plant. The first choice is usuallythe best but the most difficult. Thesecond approach, building more plant,is easier but requires that you haveadditional plant to build and that alarge chunk of money be spent at thefront end.
To find out which method wouldwork best, you try them on the compu-ter. If you are attempting to increasepenetration in your existing plant, youmust consider several things. You willhave to t ry harder Lo make each sa le .Most of the people left to sell havealready decided not subscribe. You willhave to change their mrnds. ' l 'h is mighttake the form of incentives such as freeinstallations, free service, or someform of premium. You may have toincrease your advertising budget to at-tract new customers. At the least, youwill have to knock on more doors be-fore you get a sale. These costs willhave to be considered. Fortunatelv the
S C H E D U L E 1
CUSTOMER PROJECTION
'1975 1976 1977 1978 1979 1980 198.1 19A2 1983 1984
23000 23000 23000 23000 23000 23000 23000 23000 23ooo 230009000 9000 9000 9000 9000 9000 9000 90oo gooo gooo
2 4 0 4 0 4 0 4 0 4 0 4 0 0 0 0 o240 280 320 360 400 440 440 440 440 440
1 1 6 0 0 1 3 6 0 0 1 5 6 0 0 1 7 6 0 0 1 9 6 0 0 2 1 6 0 0 2 1 6 0 0 2 1 6 0 0 2 1 6 0 0 2 1 6 0 04350 5250 6150 7050 7950 8850 a850 8850 A85o 8850
44 49 53 56 59 60 62 63 64 6460 68 72 "15
78 81 84 86 88 8952't9 6699 8279 9959 11738 13037 13437 13736 13935 140342610 3584 4431 5324 6261 7243 7512 7692 7a26 79157429 10283 12J10 15283 17999 20280 20949 21428 2176't 21949
ilI
H O M E S I N F R A N C H I S E D A R E AA P A R T M E N T S I N F R A N C H I S E D A R E AA N N U A L M I L E S O F P L A N TT O T A L M I L E SH O M E S P A S S E DA P A R T M E N T S P A S S E DS Y S T E M S A T U R A T I O N H O M E SS Y S T E M S A T U R A T I O N , A P A R T M E N T SP R O J E C T E D C U S T O M E R S H O M E SP R O J E C T € D C U S T O M E R S A P A R T M E N T ST O T A L C U S T O M E R S
The CABLEVISION FINANCIAL PLANNER is a computerized f inancial model designed toprovide the system operator with vital information you need, along with options whererequired. The complete financial plan for any given system is approximately a dozen pageslong, and it covers all aspects of the system's growth, financial requirements, cash flow andrate requirements. Although the sample page from the example system shown here is for afairly extensive system (23,000 potential homes), the system is cash-cost viable for very smallsystem potentials down to as few as 500 homes.
CATJ for
computer program is set up to handlesuch problems. Two of the normal en-tries are percent-fre e-installntians andthe cost to add a new subscriber.
Building new plant is also easy tocalculate. Once you enter the cost permile, mi les of plant to be bui l t , and thenumber of homes passed, the computerdoes the rest. It will calculate the num-ber of subscribers you should get, therevenue created, any additional ex-penses required such as more instal-lers, tech or office help, increased loansor payments and all the other thingstha t w i l l a l fec t your f inanc ia l p ic tu re .The result is two tables: one showingvour prof i t -and-loss posiLion, the otheishowing cash flow.
The other major way to increaserevenues is to raise your rates. That,at least, is obvious, but how do youdetermine how much is enough, orwhir :h rates to increase? Well , voucould si t down and work out a com-plctc budget, but i f you have ever
lnirdc onc project ion-much less sev-cral vur iat ions on a theme-vou knowhor , r n t r r< ,h work tha t invo lved.
Much of what you need is already inthe program. It was designed to in-crease rates to offset inflation. If voute l l the mach ine to inc rease your ra lesever.y four years, or whatever periodyou think wi l l be reasonable, i t wi l lautomatically calculate the effect of in-f lat ion on labor and mater ials, and thenraise your rates to compensate. If youwish to raise only certain rates, sayprinary rates and advert is ing rev-cnu( ' . you jus t inpu l thc new ra tes .Then you ei ther increase or decreasethe rates unt i l you f ind the opt imumrate schedule. Using the computer,you can try several variables in lesst ime than i t would take you to prepareonc proiect ion by hand.
So lar we have only talked aboutusing a computer ized f inancial pro,g ranr to he lp an owner o r manager inan exist ing system make his day-to-
SCHEDULE 3
REVENUE ASSUMPTIONS
M O N T H L Y R A T E , P R I . O U I L E T . H O M E SM O N T H L Y R A T E . P R I . O U T L E T A P T S .M O N T H L Y R A T € S E C . O U T L E T H O M E SM O N T H L Y R A T E , S E C . O U T L E T . A P T S .C O N N E C T I O N F E E . P R I M A R Y . H O M E SC O N N E C T I O N F E E P R I M A R Y A P T S .% F R E E I N S T A L L A T I O N P R I M A R YC O N N E C T I O N F E E . S E C O N D A R Y H O M E SC O N N E C T I O N F E E . S E C O N D A R Y . A P T S% F R E E I N S T A L L A T I O N . S E C O N D A R YM O N T H L Y R A T E - P A Y T VP A Y T V D E P O S I T R E O U I R E DP E N E T R A T I O N G R O W T H . H O M E SP E N E T R A T I O N G R O W T H . A P T S .
1 2 3 4 5 6 7 I I 1 05 . 9 5 5 . 9 5 5 . 9 5 7 . 1 0 7 . 1 0 7 . 1 0 1 0 . 1 0 1 0 . 1 0 1 0 . 1 0 1 7 . 1 01 . 5 0 1 . 5 0 1 . 5 0 . 1 . 8 0 1 . 8 0 1 . 8 0 2 . 6 0 2 . 6 0 2 . 6 0 4 . 4 01 . O 0 1 . 0 0 1 . 0 0 1 . 2 0 1 . 2 0 1 . 2 0 1 . 7 5 1 . 7 5 ' t . 7 5
3 . O O' 1 . s 0 1 . 5 0 1 . 5 0 1 . 8 0 1 . 8 0 1 . 8 0 2 . 6 0 2 . 6 0 2 . 6 0 4 . 4 0' 1 0 . 0 0
1 0 . 0 0 1 0 . 0 0 1 1 . 9 s 1 1 . 9 5 1 1 . 9 5 1 7 . 0 0 1 7 . 0 0 . l 7 . O O 2 8 . 7 5
1 0 . 0 0 1 0 . 0 0 1 0 . 0 0 1 1 . 9 5 1 1 . 9 5 1 1 . 9 5 1 7 . 0 0 1 7 . 0 0 1 7 . 0 0 2 A . 7 50 0 0 0 o o o o o 0
5.O0 5.00 5.00 6.00 6.00 6.00 8.s5 8.55 8.55 14.455.00 5.00 s.oo 6.00 6.00 6.00 8.55 8.55 8.55 14.45
o 0 0 0 o o o o o o6 . 0 0 6 . 0 0 6 . 0 0 7 . 1 5 7 . 1 5 7 . 1 5 1 0 . 1 5 1 0 . 1 5 1 0 . 1 5 1 7 . , 1 5
35.00 35.00 35.00 41.70 41.70 4.t .70 59.20 59.20 59.20 1oO.O50.45 0.50 0.55 0.60 0.65 0.65 0.65 0.65 0.65 0.650.60 0.70 0.75 0.80 0.85 o.9o O.9o O.9o O.9o O.9o
Th.e primary advantage to the computerized technique is not the slick appearing computerprint-out of the numbers, but the immediate flexibility which the system operitor has inanalyzing changes in the input numbers. Fgr example, i f the system study is bui i t upon a $5.9brate initially, what happens if the rate is increased to $7.10 in the fourth year? The answer islaborious to calculate, and very time consuming. With the assistance of a computer, it isalmost instantaneous and the computer run time is usually far outweighed, as a cosi factor, bythe immediate answers and the accuracy of the answers.
J U N E , 1 9 7 5 41
day decisions. What about a new svs-tem?
- Any new system faces unique prob-lems. The first and most impoitantproject is to develop a complete plan ofexactly what you want to do. Morethan at any other time it is essential toplay "WHAT IF." What if plant costsgo up ? What if our penetration growthis a few percentage points better? Orworse? What rates will we need? Whattype of equipment can we afford?Should we add local origination at firstor wait unt i l we have bui l t up a sub-scriber base? What effect will inflationhave? What type of loans can we han-dle'/ How much capitalizaLion will berequ i red?
Al l of these quest ions must be an-swered even before yov apply for afranchise. If you already have a fran-chise, you must live within it, but yousfu.ll have options available.
Sooner or later you'll reach the pointwhere .you have to sit down before thepeople with the money and show themhow you expect to make a profit. If youcan show them a complete proformawhich considers all facets of buildingand operating a system, they will bemore likely to ksten to your proposal.If you can also show them that youhave considered alternatives such asvarious financing packages or what ef-fect changes in saturation, inflation, orvarying interest rates would have onyour system, they will be even morelikely to fund your project.
When planning a system you shouldstart as early as possible. Often a fran-chise is offered on a "bid" basis. Gener-ally the city issues guidelines outliningwhat they want and sometimes evenspecifying rates. Usually the rates aresimply a number pul led out of the airor used because "everyone else gets$4.95r" If you develop your proposaland find that the system simply can'tbe a financial success at those rates,you are faced with three choices. First,you can agree to the conditions, try to
42
live with the rates, and lose monev.Your second choice is to agree to theconditions, build your system, andthen fail to live up to your obligations.This has been tried in the past, butnow cities are starting to get a Uttlehuffy. They expect us to start deliver-ing some of that blue sky we promised.
The third option is to try to eonvincethe franchising authority that eitherthey are asking too much or the ratesare too low. This is a difficult thing todo, and you risk losing the franchise tosomeone who promises the world, butit's the best approach. All the data youcan get is just .not enough though.Here particularly, a compuierized pio-forma is a necessity. If you can showthe franchising authority in trlack andwhite what the problems are and whatsolutions are possible, they will knowtwo things about you. First, that youplan to make a success of the system intheir town, and second, that you haveseriously considered what is requiredto bring the best cable service to them.
Once you have decided on your sup-plier and have located funding, you areready to build. As your system grows,you will find even more uses for a com-puterized proforma. By regularly up-dat ing the data input to the computerand recalculating your projections, it ispossible to keep track of exactly whereyou stand. You can spot trends devel-oping before they become problems,and take advantage of changes.
Today a system manager must bepart politician, part engineer, partfather figure, and above all, accoun-tant. To make a system succeed, everydollar must go as far as possible. To dothat, the manager needs all the infor-mation he can get. By using a compu-terized financial planner, even thesmallest system can afford to explorethe options available. Now, the timethat was spent trying to put togetherbudgets and projections can be spentmaking the decisions needed to makethe system more profitable.
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Time, temperaturA, barometr ic pressure,wind veloci ty , wind di rect ion and four (4!)card di$play spots vf i th a Sony AVC-1400(2:1 inter lace) camera. Uni t f eatures unid i -rect ional c lockwise-scanning sequence and isdesigned for long torm, 24 hour per dayusage and a minimum of maintenance.* - Deluxe model wi th Texas Electronics in-struments avai lable at addi t ional cost .
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IJ U N E , 1 9 7 5 43
WHAT A FEW PEOPLE HAVESAID ABOUT THE MARCH/
APRIL ISSUES OF CATJEdilor 's Note: CATJ received several hundred letters
from broadcasters, educators, iournal ists, Congressmen,CATV people, etc. lol lowing the March and Apri l issues olCATJ. Most were purely laudatory, and while we d0appreciate the nice commenls, we see no useful purposein f i l l ing valuable CATJ page space with letter after lel teratter lel ler 0l congratulat i0ns. We did not acknowledqeeach one individual ly, so al low us t0 d0 so here with a"thank you for your kirrd comments" lo al l who wrote.
We wil l share a few ol the letters received. here.however, where lhey are ol an informalional nature.
Editor:
Your March 1975 issue, w i th the in -depth s tudy o f thebackground o f TV a l loca t ions , g laddens my hear t . For on?age 42 | Iound in p r in t fo r the f i rs t t ime acknowledge-ment of a TV/Radio I irst which I inst igated and sawthr0ugh success fu l l y . Th is p r0gram was, I be l ieve , thesa lva t ion o f many smal l marke t UHF s ta t ions .
I was General lVlanager f0r D0nrey lVedia Group, opera-to rs o f KFSA AM/F lV l and CP h0 lder lo r UHF channe l 22 in.F0rt Smith. Arkansas. 0ur problem was gett ing networkprogram delivery from AT&T. We wrote to the tele0h0nec0mpany in S t . Lou is t ime and t ime and t ime aga in ask inglo r re l ie { . They never answered a s ing le le t te r . Theyalways sent a man down to talk with us, so there would be"n0 permanent record o f h is te l l ing us 'n0 ' on the mat te ro{ mic rowave re l ie l " .
So I requested 0f the corporati0n president, and re-ce ived h is permiss ion , t0 ins ta l l a 0 .1 wat t Ray theon mi -crowave unit on our own midway belween Lit i le Rock(where netowrk service was avai lable) and Forl Smith. ontop 0 f a 3 ,000 foo t mounta in . 0n the mounta in too wepicked ofl the Lit t le Rock network signal from a Lit t leRock s ta t ion , and then beamed i t on to F t . Smi th 47 mi les .The gran t lo r the "exper iment " came th rough jus t in t imefor the World Series. 0ur demodulator was an ordinarvte levrs ron rece iver and we went in to i t to b r inq aud io andvideO oul f0r lhe microwave tranSmitter.
I am 0n the cable side n0w, alter 40 years as al lroadcaster. I 've copied a lot of good ideas other peoplehave originated. But I lust wanted someone to know thisone or ig ina ted w i th me, and lam proud o f where i t led .
H. Weldon Stamps
Basical ly Fr iendly
Presidenl I bel ieve the cable television industry is curreni ly over-Jeky l l Cab le , lnc . regu la ted by the Federa l Communrca t ions Commiss ion . InJeky l l l s land, GE. o rder to a l lev ia te th is p rob lem, I have ins t ruc led my s ta l f
Editor:
Some confus ion fo r me 0n "CBS be inq an o f fshoot 01RCA . This may be true, way. way back-. But I seem torecal l that either the red or blue network became ABC(rad io ) ; no t CBS. Am I wr0ng? Inc identa l l y , tha t was agreat . g rea t j0b on the FCC "conJus ion" th rouqh theyears . I w ish every subscr iber . government o f l i c ia l ( loca l )and Congressman cou ld read Vour l \ Ia rch /Apr i l i ssues .
Jac k SandstromFayette TV Cable, Inc.
Un ion town. PA.Reader Sandstrom is correcl; ABC (not CBS) was the
creal ion ol the radio network spl i t t ing 0f the early NBCmull iole radio networks.
Ed i tor:
Having just read your Apri l 1 975 issue of CATJ, I f ind i td i f f i cu l t t0 comprehend your log ic ; log ic dea l ing w i thdegradation 0f television broadcasting, networks, et al.l \4y question is Where would Cable TV be today withoutte lev is ion br0adcas t ing? Ac tua l l y , where wou ld you andCATJ be with0ut lelevrsion broadcasl ing and Cable TV?
She ldon F . S tor r ie rSec retary-Treas u rerWKTV Channel Two,
Cent ra l New york Cab le TV. Inc .Ut ica . New York
The same place you would be; l istening t0 lhe red 0rblue radio nelworks 0n our Atwaler-Kent l iv ing room con-sole. Arguend0, where would Hii ler be without World WarTwo?
Ed itor:
Unti l the Apri l issue of CATJ arr ived, I had no idea thatthe television stat ions owned by the three major networkshad succeeded in obtaining such an exorbi lant prol i ll eve l . 0u i te f rank ly , i t does appear tha t the FCC has been0verzea l0us in the issuance o f unwar ran ted and un ius t i -f ied regu la t ions .
Senator Henry Be l lmon
Edi t ' r : wash inq ton ' D C '
CATJ for44
t0 under take a s tudy o f cab le te lev is ion and i l s needs . Wewi l l inves t iga te ex is t ing Commiss ion ru les govern ing theindus t ry t0 de termine wh ich measures are in the bes tin te res t o f bo th cab le sys tems and the pub l ic wh ich theyserve . In add i t ion , we w i l l look a t whether cab le shou ld beregu la ted on the federa l , s ta te o r loca l leve ls , and whetherth is regu la l ron has impa i red the growth and deve l0pmento f CATV. H0pefu l l y , the recommendat ions o f the Subcom-mi t tee w i l l ead to the in t r0duc t i0n 0 f leg is la t i0n tha t w i l ld rect lV address the problems t0 which CATJ refers.
Torber t H . MacDona ld . M C.Cha i rman, Subcommi t tee on
Communica t ionsEditor 's N0te: CATJ/CATA received m0re than 130
similar letters lrom Senators and Congressmen fol lowingthe March and Apri l issues ol CATJ.
Editor:
I wou ld l i ke t0 p rOtes t the cover 0J the Apr i l /5 CATJ,usrng a q !01e t rom the B ib le in a jok ing manner . Cer ta in lyyour pe0p le nave be t te r resources fo r use in the Journa lthan o f fend ing Chr is t ians w i th such abuse o I God 's word .
Roder ick LuomaWJBK TV
Det ro i t , lV ich iganProlesl acknowledged. Respectlul ly, the quotation was
not intended as a j0ke. Nothing could be more seriousthan the surv iva l o l CATV t0 10 ,000,000 U.S. cabte-served househo lds . As fo r a be t te r resource . . . lhan theBible ?
C L A S S - l - C A T R A T E S : C t a s s i f i e d a d v e r t i s i n q s p a c ei s a v a i l a l l l e a t 8 c e n t s p e r l e t t e r o r s p a c e b e t w e e nw o r d s . T y p e o r p r i n t i n s e r t i o n r e q u i r e d . a d d t h et o t a l n u m b e r o f t e t t e r s a n d s p a c e s b e t w e e n w o r d sa n d m u l t i p l y b y B c e n t s . E n c t o s e f u l l p a y m e n t w i t ha d v e r t i s e m e n t . T h e d e a d t i n e i s t h e 2 O t h o f t h em o n t h p r e c e d i n q t h e p u b l i c a t i o n i n w h i c h y o u w i s hy o L r r a d t o a p p e a r . C A T J b o x n u m b e r s ( f o r t h e f o r -w a r d i n q o f r e p l i e s ) a r e a v a i l a b l e a t $ 5 . O O p e r i s s L t e .S e n d i n s e r t r o n s t o C A T J C L A S S - I - C A T S . 4 2 0 9 N W2 3 r d S t r e e t , S u r t e I O b , O k t J t r u m J C i t y , O k . 7 J l O , / .
HELP WANTED-Manager/Chief Techni-cian wanted to run small CATV system (un-der 1,000 connects) in southeastern USA.Musl be malure, responsible, self start ingindividual. Send complete data in confidence,including resume and salary requirements, toBox J1, o/o CATJ, 4209 NW 23rd. Suite 106.Oklahoma City, Oklahoma ?3107.
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wHo CARES. . .To pro tec t your CATV head end orCATV p lan t f rom t rans ien ts andsurges caused by l igh tn ing , s ta t i ccharges , o r sw i tch ing . . . you needMin i -Mizer p ro tec t ion .
M i n i - M i z e r h a s a f u l l o n eyear guarantee , pa ten ted c i r -cu i t ry tha t rese ts a f te r eachsurge/ t rans ien t ac t i va tedevent , and a counter tha t re -por ts the number o r events .BROWN ELECTRONICSArtemus RoadBarbourville, Ky. 40906(606) s46-5231
if the f i rst t ime wipes out yourhead end or a section of CATVplant !
M i n i - M i z e r i s a v a i l a b l e i n t w o n e wheavy-duty mode ls (SP-500/3600w a t t s ; S P - 3 0 0 / 1 8 0 0 w a t t s ) o l u ss t a n d a r d - d u t y m o d e l s . A m o d e l t of i t every load cond i t ion , f rom headend to p lan t power ing s ta t ions !
Ava i lab le fo r po le mount ing(w i th cover ) , head endm o u n t i n g ; 1 2 0 V A C , o r 1 2 0 /240 VAC s ing le phase powerc i r c u i t s . H u n d r e d s i n u s ethroughout the count ry inmore than fo r ty CATV sys-tems! Wr i te fo r da ta sheets .
IJ U N E , 1 9 7 5 45
An ix l e r -P ruzan . I nc . . 1963 F i r s t Ave . S . . Sea t t l e , WA. 98134 (D ' .Avan lek . l f c . , 3175 Bowers Avenue , San ta C la ra , CA . 95051 (M8 )Be lden Co rp . . E l ec t r on i c D i v i s i on , Eox 1327 , R i chm0nd , lN .4 /3 /4 (M3 )BROADBAND ENG NEERING. lNC . , 850 0 l d D i x i e H ighway , Lake Pa rk , FL . 33403 (Dg , r ep tacemen t pa r t s )Bu rnup & S ims . Box 2431 , W. Pa lm Beach , F1 .33401 (S2 , S7 , S8 )[ ] , r l l l e [ )V fan l cs . I nc .501 F0 f i ] es Bvd . So San F ranc i sco , CA 94080CABLE NEWS. 2828 N 36 lh S t ree l , Phoen i x , AZ . 85008 (56 )0e r r0 Con rmunca l r0n P roduc l s . Ha l l s l i l i l l Road . F reeh0 ld , NJ 0 i 729 (M3 , M5 . M7 )00 lV l \ 4 /SC0PE C0 IVPANY, P .0 . Box 2406 . H i ck0 ry , NC .28601 (M3 )Je r r y Conn & Assoc ia tes ,550 C leve land Ave . , Chambersbu rg , PA . 17201 (03 ,05 ,06 , D7 )C -C0R ELECTRoNICS , I nc . , 60 Dec ibe l Rd . , S ta re Co i l ege , PA i 6801 (M t )DAVC0 . I nc . . P0 Box 861 , Ba tesv i l e , AR . 72501 (D l , S1 , 52 , 58 )UEV NES Trai ers & Accessor ies, Grantv i le, PA. 17028 (M9, cable l ra i lers)ENTB0N. I nc . . / 0 31 84 th S t ree t , Genda le . NY 11227 (M4 , M5 , 04 , 05 , S8 )l iA l v (10 N I I I JSTR tS , INC , 317 Ccx S t . Rose le NJ . 07203 (M5 )JERB0LDE lec l r on i csCo rp . , 200Wi tme rRqad . Ho rsham, PA .19044 (M l , M2 , M4 , M5 , M6 , M7 , D3 ,08 , 51 , 52 , 53 ,S8 lKay Een le l r i c s Co fp , 12 Mape Avenue , P ine 8 rook , NJ . 07058 (M8 )Microwave Fi l ler Co., 6743 K nne St . , Box 103 E. Syracuse, NY. 13057 (M5, bandpass l i t ters)M ID STATE Commun ica l i ons , I nc . , P .0 . Box 203 , Beech Grove ,1N .46107 (M8 )PrO Com Electronics, P.0. Box 42l , Pauqhkeepsie, Ny. 126010E Manufactur ing C0., BOx 227 New Ber l in, PA., 17855 (M9, t00ls & equipment)BMS CATV D i v i s i on ,50 An l i n Pace , B ronx . NY . 10462 (M5 , M7 )TEXSCAN Co rp . . 2446 N . Shadeand Ave , nd ianap0 l i s , lN 46219 (M8 , bandpass f i l t e r s )The la -Com, P 0 . Box 9728 , Phoen i x . AZ 85068 (M1 , M4 , M5 , M7 , M8 , 51 , S2 , 53 , 58 , AML M ic rowave )T imes W i re & Cab le C0 . , 358 Ha l l Avenue , Wa l i ng fo rd . C f 06492 (M3 )T 0 N E R E q u i p m e n t C 0 . , 4 1 8 C a r e d e a n D r i v e , H 0 r s h a m , P A 1 9 0 4 4 ( 0 2 , 0 3 , 0 4 , D b , 0 6 , D 7 )WAVETEK Indiana, 66 N. Fi rst Ave. , Beech Grove, N. 4610/ (M8)
N0TE: Supp ie f a reas are keyed a t the end 0 f each is l inq , as f0 lows
Distr ibutors:
D l Fu I CATV equ pmen l l i neD2 CATV antennast l3 CAIV cableI)4 CATV ampl i f iersDb CATV passrves116 CATV hardwareD/ CATV conneclofsDB CATV l es t equ ipme f t
Manulacturers:
l \41 Ful CATV equipment l inel \ .42- CATV antennas[43 CATV cablel \44 CATV ampl i f erslV5 CATV passivesM6 CATV hardwarel \ / l7-CATV connectorsl \ / l8 CATV test equipment
Service Firms:
S1 CATV conlracl ing52 CATV consl fuct on53 - CATV l i nanc lng54 CATV sof twareS5 CATV t l r l l rng servtces56 -CATV pub l i sh i ngS/ CATV drop instal at tonSB CATV e fg i nee r i ng
N E W R M S U N I T A P - ' R M S E l e c t r o n i c s , I n c . ,
5 O A n t i n P l a c e , B r o n x , N e w Y o r k 1 0 4 6 2 h a s
i n t r o d u c e d a n e w i n l i n e m u l t i - t a p c a l l e d U n i t a p .
T h e n e w t a p u n i t h a s " 1 3 n e w e n g i n e e r i n g c o n -
c e p t s f o r i n l i n e m u l t i - t a p d e s i g n u n i t s " a c c o r d i n gt o K e r w i n M c M a h o n , G e n e r a l S a l e s M a n a g e r , T h e
u n i t s a r e a v a i l a b l e f o r s t r a n d o r p e d e s t a l m o u n t i n gw i t h i n t e r c h a n g e a b l e t a p p l a t e s .
46
A c c o r d i n g t o R M S " i n i t i a l c u s t o m e r a c c e p t a n c eo f t h e n e w t a p h a s b e e n s o b r i s k t h a t o r d e r s f o r t h en e w u n i t c a n o n l y b e a c c e p t e d f o r a g O d a yg u a r a n t e e d d e l i v e r y b a s i s , i n i t i a l l y " . F u l l i n f o r m a -t i o n o n t h e n e w t a p i s a v a i l a b l e f r o m R M S .
J E R R O L D l S B U S Y - J e r r o l d E l e c t r o n i c sC o r p o r a t i o n , 2 0 O W i t m e r R o a d , H o r s h a m , P a .1 9 0 4 4 h a s a n n o u n c e d a n u m b e r o f c h a n g e s i n
CATJ for
b u s i n e s s p o l i c i e s r e c e n i l y , w h i c h d i r e c i l y a f i e c tJ e r r o l d c u s t o m e r s w o r l d w i d e ,
T o p r o v i d e f a s t e r , i m p r o v e d p a r t s a n d r e p a i rs e r v i c e s , J e r r o l d h a s e x p a n d e d i t s p a r t s a n d R e _p a i r D e p a r t m e n t s ; a n d C O N S O L T D A T E D t h e s ed e p a r t m e n t s a t K a n s a s C i t y , M i s s o u r i .
A c c o r d i n g t o R a y m o n d p a s t i e , J e r r o l d ' s N a -t i o n a l S a l e s M a n a g e r , t h e n a t i o n a l h e a d o u a r t e r sf o r r e p a i r a n d p a r t s i s n o w l o c a t e d a t ( J E R _R O L D E L E C T R O N T C S C O R p O R A T T O N / F A C _T O R Y P A R T S A N D S E R V I C E F A C I L I T Y ) . 1 3 2 2A T L A N T I C A V E N U E , N O R T H K A N S A S C I T Y ,M I S S O U R I 6 4 1 1 6 . M a n a g e r o f t h e e x p a n d e df a c i l i t y i s H a p W a m p l e r a n d t h e t e l e p h o n e n u m b e ri s ( 8 1 6 ) 8 4 2 - 1 1 3 0 . T h e e x p a n d e d K a n s a s C i t yr e p a j r f a c i l i t y / p a r t s f a c i l i t y r e p l a c e s t w o o t h e r l o -c a t i o n s f o r p a r t s a n d s e r v i c e l o c a t e d i n R e d w o o dC i t y ( C a l i f o r n i a ) a n d C h i c o p e e ( M a s s a c h u s e t t s ) .T h e R e d w o o d C i t y f a c i l i t y c o n t i n u e s t o h a n d l ew e s t c o a s t s a l e s .
J e r r o l d ' s W i i l i a m L a m b e r t , v i c e p r e s i d e n t a n dd i v i s i o n m a n a g e r o f J e r r o l d ' s C A T V S y s t e m s D i v i -5 t o n , n a s a n n o u n c e d a n e w , , d e s i g n s e r v i c e f o r n e wS y s t e m s , s y s t e m r e b u i l d s a n d s y s t e m e x t e n s i o n sf o r B i l l - o f - M a t e r i a l ( d i s t r i b u t i o n ) s y s t e m s ' , . U n d e rI n e n e w p r o g r a m , J e r r o l d w i l l c o n t i n u e t o d e s i g nS t a r l i n e 2 0 a n d S t a r t i n e 3 O d i s t r i b u t i o n s y s t e m s o na n o - c n a r g e b a s i s . A s a B O M s y s t e m i s c o n s t r u c t -e d , a n y c h a n g e s i n e q u i p m e n t l o c a t i o n o r c a b l er o u t i n g i s n o t e d o n t h e d r a w i n g s s u p p l i e d b y J e r _r o l d , b y t h e c o n s t r u c t i o n p e r s o n n e l , T h e n , a f t e rc o n s t r u c t i o n i s f i n i s h e d , i f t h e s y s t e m w i s h e s t oh a v e t h e c o n s t r u c t i o n d r a w i n g s w i t h c h a n g e s i n -c o r p o r a t e d - d u r i n g - c o n s t r u c t i o n f i n a l i z e d i n t o a s e to f " a s - b u i l t " m a p s , t h e m a p s c a n b e r e t u r n e d t oJ e r r o l d i n H o r s h a m f o r r e - d r a w i n g , A f e e o f$ 3 5 . O O p e r m i l e f o r r e - d r a w i n g w i l l b e c h a r g e d ,a n d f o r a n e x t r a $ 1 . O O p e r m i l e , 1 1 x l 7 i n c hr e p r o d u c i b l e s c a n b e s u p p l i e d i n b o o k l e t f o r m .
F u l l i n f o r m a t i o n o n t h e n e w p r o g r a m i s a v a i l -a b l e f r o m W i i l i a m L a m b e r t a t J e r r o l d ' s H o r s h a mof f i ce .
J e r r o l d ' s R o b e r t D . E i s e n h a r d t , J r . , p r e s i d e n to f J e r r o l d E l e c t r o n i c s , l n c . h a s a n n o u n c e d t h a th i s f i r m i s i n t r o d u c i n g a C h a n n e l C o m m a n d e r" E " , a s p e c i a l h e a d e n d p r o c e s s o r t a i l o r e d t o t h e( l a r g e l y ) E u r o p e a n C C I R s t a n d a r d s . T h e n e w . , E ' ,v e r s a o n C o m m a n d e r i s s i m i l a r t o t h e n e w C h a n n e lC o m m a n d e r l l t u n i t r e c e n i l y s h o w n i n t h e U n i t e dS t a t e s a n d C a n a d a . h e a d e n d u n i t f o l l o w so n t h e h e e l s o f t h e i n t r o d u c t i o n i n E u r o p e o f t h eS t a r c o m - 3 3 c o n v e r t e r ; w h i c h h a s a l s o b e e n e n g i -n e e r e d t o C C I R s t a n d a r d s . J e r r o l d s a l e s a n d o t h e rE u r o p e a n m a t t e r s a r e h a n d t e d b y J E R R O L D l N _T E R N A T I O N A L , 7 0 C H A U S E E D E C H A R L E R O I1 0 6 0 B R U S S E L S , B E L G t U M .
AN ANSWER TO YOURREPAIR PROBLEMS...
NOW!C-COR of fe rs comple te repa i r and tes t_ing o f a l l manufac turer ' s CATV amol i_f i e r s . C - C O R s e r v i c e f e a t u r e s i n c l u d e :
. R E P A I R S E R V I C E .
. C A B L E T V A M P L I F I E R S .
. A L L M A N U F A C T U R E R S .
. O U I C K T U R N A R O U N D .o T E S T E D : N O t S E , R E S P O N S E . G A t N .. X M O D , 2 I M , 3 I M .
R E P A I R E D T O O R I G I N A L S P E C S .
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*A R ichey Deve lopment CompanyModu la to r to pu t the weather ma-c f i ine on the VHF channe l o f vourc h o i c e
.A R ichey Deve lopment Company Co l -o r -Adder (makes a b lack and wh i tec h a n n e l r e d , b l a c k a n d w h i t e ! )
THAT'S WHAT Y()U GETFoR $1250 .00 ! ! !
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We have enough fa i th in our products,our people and our customers to put i t inwr i t ing. Not just a warranty, but a wr i t tenperformance guarantee. The only one in
the industry. When you buy the Super-Connector , the Superwarranty
comes wi th i t , for no addi t ional charge.We tell you what you can expect and
guarantee that you' l l get i t .
We thrnk thrs rs the way everybodyshould do business. Someday maybeeveryone wi l l . lv leanwhi le, isn t i t n ice toknow that somebody th inks enough of theirproduct to put i t in wr i t ing?
We also say this: You can pay a lot moretor your connectors. You can't buy abetter connector.
Cambridge. The Superconnector .
GambridqeProducts-
1 0 1 F o l e y S t , S o m m e r v r l l e M a s s 0 2 1 4 5 , ( 6 1 7 ) 6 6 6 - 3 3 4 3A t l a n t a , G a . S r m r V a l l e y C a l i f . T o r o n t o . C a n a d aI n E u r o p e H - G D l t a l r a . C i s t e r n a D i L a t / n a . l t a l y
A substdiary ol Cambildge Scrcw Company, a HrG Company. cII
