Latour's Patents Control Radio Weather Controls Radio Alai

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May 1, 192515 Cents a Copy

A Selective Honeycomb Hook-upBy HORACE V. S. TAYLOR

Keep Your Tubes in Good HealthLatour's Patents Control Radio

Distortion a Good Thing---Some-timesWeather Controls Radio Alai

YOU WILL UNDERSTAND THISMAGAZINE__ AND WILL LIKE IT

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PUBLISHED TWICE A MONTH

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Which is BetterA Cheap Set for Cash ---orA GOOD Set ON TERMS

The Good Set is Cheapest in the End

Bay State specializes on the better gradesets, like Radiola. DeForest, Adler Royal,Magnavox, and sells on Convenient Terms.

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RADIO PROGRESSHORACE V. S. TAYLOR, EDITOR

Volume 2 Number 4

Contents for

MAY 1, 1925

PAGE.

A SELECTIVE HONEYCOMB HOOK-UP

AMERICAN RADIO RELAY LEAGUE 8

WEATHER CONTROLS RADIO ALARM 9

EXIT-MICROPHONE FRIGHT 12

KEEP YOUR TUBES IN GOOD HEALTH 13

LATOUR'S PATENT'S CONTROL RADIO 17

DISTORTION A GOOD THING-SOMETIMES 20

EDITOR'S LOUD SPEAKER :

FOOLING OLD MAN STATIC 23

NEW RADIO COLLEGE FOR WOMEN 25

RADIO-THE DOCTOR OF THE DEEP 2 7,

DR. RADIO PRESCRIBES 29

FONE FUN FOR FANS 30

RADIO PROsuEss is issued on the 1st and 15th of each month by the Oxford Press at 8 Temple Street,

Providence, Rhode Island. John F. O'Hara, Publisher. Yearly subscription in U. S. A., $3.00. Outside

U. S. A., $3.50. Single copies, 15 cents. Entered as second-class matter, April 4, 1924, at the Post Officeat Providence, R. I., under the Act of March 3, 1879. Address all communications to RADIO PROGRESS,8 Temple Street (P. 0. Box 728), Providence, R. I. Title registered at United States Patent Office.

The publishers of this magazine disclaim all responsibility for opinions or statements of contributorswhich may at any time become subjects of controversy.

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QUALITY and distance are what a radio set must give. To insure Quality,amplification without distortion is essential. And to insure Distance, lowlosses are essential. That is radio in a nutshell.

People in whose sets Acme Transformers are used, are sure of hearingconcerts "loud and clear" so a whole roomful of people can enjoy them.

The Acme A-2 Audio Amplifying Transformer is the part that givesquality. It is the result of 5 years of research and experimenting. It givesamplification without distortion to any set. Whether you have a neutrodyne,super -heterodyne, regenerative or reflex, the addition of the Acme A-2 willmake it better.

To get the thrill of hearing distant stations loud and clear, your set musthave low losses, for it is low losses that give sharp tuning to cut through thelocals, and it is low losses that allow the little energy in your antenna to cometo the ampifier undiminished. That's what the Acme condenser will do forany set. And it will do it for years, because the ends can't warp, the bearingscan't stick and the dust can't get in and drive up the losses several hundredper cent.

The Acme Reflex (trade mark) owes its success and its continued popu-larity to these two outstanding parts in the radio industry, for low losses andamplification go hand in hand.

Use these two parts in the set you build. Insist on them in the set you buy.

Send 10 cents for 40 -page book, "Amplification without Distortion"

WE HAVE prepared a 40 -page book called "Amplification without Distor-tion." It contains 19 valuable wiring diagrams. In clear non -technical lan-guage it discusses such subjects as Padio Essentials and Set -building; How tomake a loop; Audio frequency amplifying apparatus and circuits; Instructionsfor constructing and operating Reflex amplifiers; How to operate Reflex re-ceivers; Antenna tuning circuits for Reflex sets; "D" Coil added to Acme fourtube reflex; "D" coil tuned R. F. and Reflex diagrams; and several more be-sides. It will help you build a set or make your present set better. Send us10 cents with coupon below and we will mail you a copy at once.

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Some of the Good Thingsfor May 15

A loud speaker is always a problem. They have been far fromperfect in the past. A new style has just been invented which bidsfair to take a leading place. It is not built like the old ones. The con-struction is quite different and it is described by Vance in "A BrandNew Type of Speaker.

What are the popular sets these days? Three or five tube? Whatproportion of people use their sets in the summertime ? Are storagebatteries more popular than dry cells, and if so how do they comparein numbers? All the questions and a lot more like them are detailedat length in "Six Best Sellers of Radio."

You hear a great deal these days about short waves, or high fre-quency vibrations. Most sets can not get below 200 or 250 meters.Those that can usually are of no use for broadcasting. "A CombinedLong and Short Wave Set," by West, describes how the two may be

united into a single radio.

Doubtless you know that the government inspectors are check-ing up on the air all the time to get rid of undesirable sending stationsand to reduce interference. Many people do not understand how thisis brought about. An article by Koch, "How Radio Inspectors CatchTrouble," give the details of the method.

When you cross the ocean on a big liner, in spite of all its com-passes and logs, do you realize that the time signals are depended onto a considerable extent to find out whereabouts in the ocean thevessel is? Arnold explains how radio waves help the captain keephis bearings, in "Sailors Depend on Time Signals."

Explorer MacMillan is going up into the Arctic regions again.When he wants to hear from home he will use special short waveradio equipment. Do you know why that is required around theNorth Pole? See "High Speed Waves for Frozen North."

In wiring a set there are apt to be losses in the conductors con-necting the different units. There is a lot of mis-information on this

point. Many so-called tests are absolutely unreliable. Taylor ex-plains the reason for this in "Low Loss Wiring in a Set."

RADIO PROGRESS" ALWAYS ABREAST OF THE TIMES "

Vol. 2, No. 4 MAY 1, 1925 15c PER COPY, $3.00 PER YEAR

A Selective Honeycomb Hook -UpHere is a Sharp TunedSet Which is Easily Built

By HORACE V. S. TAYLOR

WHAT is the password in radiothese days? A year ago it was,

"Distance". Everyone was fishing foraway across the continent and the elec-tric companies reported that they wereearning extra dividends on the lightswhich were burned from eleven o'clockon up to one, two or three in the morn-ing. Two years ago, "Loudness" wasthe cry. Each chap tried to outdo hisneighbor with the amount of deafeningdin which he could throw from themouth of his loud speaker.

At the present time there is no doubtabout it-"Selectivity" is what every-one is after. This follows from the factthat there are now so many loud sta-tions going that a set which lacks thesharp tuning necessary to cut throughthe local station and pick up a distantprogram is losing a lot of the enjoymentwhich might otherwise be had. Thisquestion of selectivity is being empha-sized more than anything else by thesalesmen of high priced factory builtradios.

Has Two Advantages

The radio fan who builds his ownset is naturally interested in how hecan get results which compare withthose of the manufactured instruments.The basis of most sharp tuning dependson two things-first small distributedcapacity and second loose coupling. Theset which we shall describe, which isbased on the use of honeycomb coils,has both of these advantages.

When honeycombs are first mentionedsome of you may throw up your handsand exclaim, "Why, they passed out

two years ago." To be sure, they werequite popular and then later they fellout of style and were not used somuch. This is an illustration of howradio fashions run. It oftentimeshappens that a new piece of apparatusor a new style hook-up will be verypopular for a while and every maga-zine will carry one or two articles about

vFig. 1. A Honeycomb Coil is Like a

Banked Winding Developed

it. Then as such publications feel theneed of getting new stuff they drop thatparticular idea and rush off full tilton some other one. The latter may notbe as good as the old one was, but theneed for something original will dis-card the old standby and bring in thenovel, but inferior device.

Following Bank Coil Idea

As a matter of fact a honeycombcoil is a very efficient piece of appara-tus. As no doubt every broadcastlistener is aware, it consists of a wind-ing in which the turns do not lie snuglyside by side, but are spaced about one -eighth of an inch apart and across eachother at a slight angle. The idea was

developed from the improvementnoticed in a bank coil.

Fig. 1 shows a sketch of a two layercoil, in which a special method of wind-ing is used. It is called, "bank" andconsists in winding on a turn of thefirst layer and on top of that a turnof the second. This is repeated overand over again so that the end turn ofthe entire coil does not lie over the be-ginning. Such a method of winding re-duces the distributed capacity to a smallfraction of what it otherwise would be.

Waves Think it a CondenserThis question of distributed capacity

may be understood better if we realizethat a condenser consists of two separ-ate conductors with insulation between.In the ordinary two -layer coil the start-ing turns of the first layer serve thepurpose of one plate and the finishingfor the other. The insulation betweenconsists of the cotton or silk coveringof the wire. Since the radio waves thinkit is a condenser when they strike sucha coil they naturally behave as if con-denser capacity had been connected intothe circuit at that point.

You can readily see that this capacityaction from the first to the last turnwill not be quite the same as from thesecond to the next to the last ones. Allthe way down the line the action stillcontinues but loses force more andmore as the middle turns are connectedtogether (it being the same wire) andso no condenser effect results. Sincethis action is varying as just described,and is stretched out along the wholelength of the coil it is called "distri-buted" capacity.

6 RADIO PROGRESS MAY 1, 1925.

Makes the Tuning BroadThe effect of such action on the sharp-

ness of tuning is bad. Instead of tun-ing to single sharp frequency, as is doneby the regular condenser, which is inyour grid circuit, it has the bad effectof bringing in various frequencies and inthis way makes it hard to cut out un-wanted stations. Besides this such cap-acity is not under control as is the regu-lar condenser and so by turning the dial

AsItIAL

.0005Cp

GPr'

Fig. 2. Connections for

a primary, which is tuned by a seriescondenser, a secondary adjusted by aparallel condenser, Cs, and a ticklerwhich is advanced back and forth tovary the amount of feedback and socontrol the regeneration.How to Make a 40 -Turn HoneycombReferring once more to Fig. 2, the

primary usually is a fifty turn coil. Thisvaries, however, with the length of theaerial. If your antenna runs about 100

Honeycomb Set. Selective Because of LooseCoupling

no chance is had of adjusting for thevalue desired.

A banked coil is rather hard to windif it consists of more than two layers.It also requires a considerable amountof collodion or other dope to hold it inshape after it has been wound. To getaround these two difficulties the honeycomb coil was invented. While it is noteasy to wind by hand, automaticmachines called "universal winders"spin them off so fast that the motionis hard to follow with the eye. Theyare also self-supporting, and so do notneed very much to hold them together.

Why Sets Are SelectiveOwing to the fact that the turns are

spaced some distance apart, the con-denser action between turns is small.This combined with the fact that thecoupling between two adjacent coils issmall helps make the set, which useshoneycombs, a selective one. Even arather simple hook-up will give good re-sults for these reasons.

The hook-up which appears in Fig. 2,is a modification of a standard circuit,which gives very good results. It uses

feet or so in length, fifty turns will beright. A longer one up to 150 feet willwork better with a forty turn honeycomb. This cannot be bought but maybe easily made by unwrapping tenturns from a standard fifty turn coil.

On the other hand, if your antenna israther a short one, say fifty or sixtyfeet long, then the best results will behad by buying a 75 turn coil and un-winding ten or fifteen turns. You seethe series condenser, Cp, is able to in-crease frequency (decrease the wavelength) but can not work the otherway. When it is turned so that theplates are fully in mesh this gives youthe lowest frequency or highest wavelength which can be had. To go beyondthis point it is necessary to use morewire in the primary.

Tuned Primary is BetterOf course, it is not absolutely neces-

sary to tune this first coil to the wavefrequency coming in from the aerial.The set will work well with a so-called "untuned" primary of 35 turnswithout using the series condenser, Cp.However, considerable increase both in

sharpness of tuning and volume will re-sult by using the connections as shown.

The way you can tell whether theturns are correct in this coil is byobserving in what position of the con-denser the majority of stations come in.Perhaps you will find that the dial hugsthe zero for most stations. This meansthat the plates are turned way out ofmesh, giving as low a capacity and ashigh a frequency as possible. In thatcase take off five turns from the coiland try again. You will notice an im-provement, but if it is not enough thentake off five more turns.

When to Use Larger CoilOn the other hand you may discover

that with the condenser turned fullyinto mesh most of the stations are loud-est. This signifies that the combina-tion of aerial and coil is not big enough.If you can increase the length or heightof your antenna this is a good way toremedy the trouble. But if you havealready put up the best aerial thatyour locality permits, then the way out isto get the next larger size of coil anduse it instead. Since it is impossibleto add turns to the honey comb, buteasy to take them off, it is well tostart with a coil which you think isprobably too large and then reduce thesize a little at a time. When the rightamount of wire has been found you willget the low kilocycle waves at one

end of the dial and the high frequencyvibrations at the other, and they willbe spaced fairly well apart, so that itis easy to turn them in.

The secondary coil should be 75 turns,if you are using a condenser at Os, whichhas a capacity of .0005. The same reason-ing applies to this unit, however, as hasjust been explained in connection withthe primary. In other words, if thecoil is too big you will have to use thecondenser at the small end and con-versely. The spacing of the stations overthe dial of condenser Cs should be fairlywell apart, so that it is easy to turnthem in.

Even Spacing of StationsThe secondary coil should be 75 turns,

if you are using a condenser, at Cs whichhas a capacity of .0005. The same read-ing applies to this unit, however, as hasjust been explained in connection withthe primary. In other words, if thecoil is too big you will have to use thecondenser at the small end and eon -

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MAY 1, 1925. RADIO PROGRESS 7

versely. The spacing of the stationsover the dial of condenser Cs should befairly uniform.

The tickler will be a 35 turn honeycomb. This should be ample to getenough feedback to pull in any stationwithin range. The number of turns onthis coil has very little to do with thewave length. The more wire there isin this unit the farther apart it willhave to be spaced from the secondary inorder to prevent oscillations and squeal-ing. On the other hand, if this coil istoo small you will not be able to makethe set oscillate, even when it is pushedright up tight against the secondary.The remedy of course in such a case isto use more turns. However, if youfind that a 35 coil does not get the re-sults, it is better to look over the restof the set before using a bigger unit.

Trouble in the TubeAt this point it might be stated that

the tube itself naturally plays a veryimportant part in the amount of ticklerneeded for regeneration. If the tube isa poor one, or has not a good vacuum,or if it has the coating burned off thefilament, either from excessive voltageor from old age, then it will not oscillatereadily and a particularly big ticklercoil will be required. Instead of such alarge unit it would naturally be betterto scrap the defective tube and put agood one in its place.

Another point to be looked after incase the set does not oscillate as itshould is the bypass condenser, Cb. Thisis oftentimes omitted in many sets andas a matter of fact is not strictly nec-essary, provided that the telephonecords themselves furnish enough cap-acity so that the high frequency whichoperates the tickler is able to get tothe "B" battery and filament withoutbeing forced to thread through the biginductance or electrical weight of thephone windings. It is well, however,to use a .001 mfd. capacity here evenif not absolutely necessary, as it addsto the smoothness of operation andoftentimes reduces the tinny noise whichsome phones are known to give.

As regards the connections of thecoils the polarity or difference betweenthe two ends cuts no figure for pri-mary and secondary. It is customaryto connect the outside of the second-ary to the grid and the inside to thefilament, but this as explained will workeither way. However, when this has

once been determined then the polarityof the tickler must be made right. Aslooked at from either end the wiresleaving the grid and plate must turn inopposite directions in these coils. Thatis, if the wire from the grid spins aroundclockwise, as you look at it from theright, then the wire from the plate mustturn round its coil in the counter clock-wise direction. However, the importantpoint is not whether the grid wire goes

(This completes the primary cir-cuit.)

4 Grid condenser and leak to grid.5 Grid condenser and outside of -ec-

ondary to stator of condenser Cs.6 Inside of secondary to rotor of Cs

and over to eithe~ filament ter-minal of the tube.

This finishes the secondary circuit.7 Plate to inside of tickler.8 Outside of tickler to phone conden-

Fig. 3. This Shows the Path of Waves Through Wiring of Fig. 2

to the left or the right, but that the twocoils must be in opposite directions.

Many people prefer to get the properpolarity by trial, rather than by trac-ing out the wiring. To do this it is onlynecessary to bring tickler and second-ary coils up close together while vary-ing the secondary condenser. If variousstations are on the air you will get aseries of squeals or whistles in thephones as you rotate dial Ss. If you donot get any such whistles, then turnthe tickler coil the other way round orelse reverse the two leads. The latteris usually the easier method. If youstill get no whistles, it means that thereis something wrong with the set or tubeand you must receive, as explainedabove.

Making the Connections

As will be seen from the diagram,this is an unusually easy set to hook-up.Make the connections in this order:

1 Rotor of condenser Cp to aerial.2 Stator of Cp to inside of primary

honeycomb.3 Outside of primary to ground.

ser and phones.9 Other phone lead to plus of "B"

battery and condenser Cb.10 Minus of "B" battery

battery.Negative of

rheostat12 Rheostat to filament.13 Filament to positive of

tery. (This completesment circuit.)

Wave Paths Through the SetIt is interesting to see how the radio

waves run in such a circuit. As it issimple it is easy to grasp the path. Re-ferring to Fig. 3, the primary wavescome in at radio frequency labelled "P"and are tuned by Cp through the coil toground. The secondary waves also atradio frequency are tuned by condenserCs and fed to the grid. The outputwhich the detector tube has reduced toaudio frequency leaves the tube by theway of the plate. However, it alsocontains some of the radio frequency,which is shown by the slight ripple on

Continued on Page 8

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American Radio Relay League2,000 FREE RADIOS FOR BLINDCo-operation of a mast practical sort

is to be furnished to the AmericanFoundation for the Blind, of New York,in its plans to place radio receivingsets in the homes of blind peoplethroughout the United States. TheAmerican Radici Relay League, withheadquarters in Hartford has agreed tosupervise the installation of sets by itsmembers in the communities where theidea is to receive its first tryout.

The American Foundation for theBlind hopes to complete the installationof 2,000 radio receiving sets throughoutthe country if the% results attained inthe tryout seem to warrant it. Thus itis that members of the league werecalled in to contribute their knowledgeof radio to give the sets every chanceto prove their efficiency.

By the agreement between these twosocieties, the technical knowledge ofgood radio men in each community willassure the blind broadcast listeners thatthey are getting the most possible outof their sets. Of great importance in amovement of this sort is the fact thatthis service will be furnished free ofcharge by the League members. This willpermit the American Foundation for theBlind to apply all of the funds avail-able for radio work to the purchase ofparts, sets and material.

The plan of the foundation calls fortest installations at several strategicpoints in each state to demonstrate thevalue of it. The first work will beundertaken in twenty-four cities with atotal installation of thirty-six radio re-ceiving sets.

F. E. Handy, acting traffic managerof the Radio League, is providing theservices of members in the followingcities for this work:

Hartford, Conn.; Augusta, Ga.; Rome,Ga.; Gardiner, Me.; Herman, Mo.;Omaha, Neb.; Nebraska City, Neb.;Portsmouth, N. H.; Charlestown, W. Va.;Pittsford, Vt.; Salt Lake City, Utah;Richmond, Va.; Gould, Okla.; Greens-boro, N. C.; Lena, Miss.; Providence,R. L; Birmingham, Ala.; Davenport,Ia.; Kansas City, gas.; Grand Rapids,Mich.; New Orleans, La.; Columbia,S. C.; Fairview, Wyo.; and New Haven,Conn.

RADIOS CAN TALK CHINESEThere is a great deal of doubt as to

the legality of importing radio receivingsets into China. But in spite of it, thatcountry has twenty privately ownedbroadcast stations and 5,000 listeners,as reported by the American RadioRelay League. "The Chinese Press,"after making a thorough investigationon behalf of its readers admits franklythat it does not know whether import-ing completely assembled receivers is

legal or not.It is said that the Chinese government

issued an edict against the importationof "military" equipment, and in somequarters this term has been applied toradio sets. The customs authoritieshave refused to admit assembled sets,and it is rumored that a considerablestock has been seized and held by them.However, several companies in Shang-hai are selling receivers openly upon in-structions of consular and diplomaticofficials that the government cannotclassify radio sets as military equip-ment. The number of persons inter-ested in radio is increasing constantlyaccording to the "Press," which statesthat it receives inquiries upon the sub-ject almost daily. It does not attemptto explain how the several thousand re-ceiving sets now in use got into China,or how they were obtained by local com-panies. The assumption is that theparts have been imported as "electricalmaterials" and assembled by the dealersthemselves.

In order to keep up with the publicdemand, which is insistent, magazinesand newspapers following the exampleof those in the United States and manyother countries are printing no end ofhook-ups and instructions for buildinghome-made sets.

A SELECTIVE HONEYCOMBHOOK-UP

Continued from Page 7top of the slow audio wave. This out-put runs through the tickler coil, wherethe radio ripple reacts with the second-ary coil to cause the feedback. The audiofrequency has no effect in this coil ow-,ing to the small number of turns.

From there both radio and audiotravel along to the point X. Bypass

condenser Cb allows the radio vibrationto be short circuited around the phonesbut the slow audio oscillation can notpass such a small capacity. Instead itis forced through the phones where itmakes the diaphragm vibrate to give usmusic. The two frequencies unite againat Y and after passing the 'B" batteryreturn to the filament.

To operate this set adjust the ticklercoil until it is close to the secondary.This will cause the set to oscillate, asshown by a slight roughness or squeal-ing. Move the secondary immediatelyaway again until the oscillations juststop as otherwise you will be disturb-ing your neighbors. Then turn Cs

until a station is heard. The primarycondenser Cp may now be adjusted togive loudest volume. A slight shift ofcondenser Cs will then bring the stationout clearly.

Loudness vs. SelectivityThe primary coil is to be placed up

close to the secondary to give the loud-est volume. However, this position isnot best for selectivity. The sharpesttuning may be had by separating thecoils P and S by an inch or two. How-ever, what you gain in selectivity isbound to be lost to some extent in loud-ness. After making changes in the set-ting of the coil it is well to readjustcondensers Cs and Cp to the best posi-tion.

In conclusion, it may be said that foran easily built set, which possesses goodselectivity and an adjustable volume,it is hard to beat this hook-up. Themost serious disadvantage is that ad-justing the amount of feedback andtickler action by changing the positionof the tickler coil is not as neat or aseasily made as the more customary wayof changing the rotor of the vario-coupler.

HELPING HONEY HARVESTOne hundred and twenty-five broad-

casting stations are assisting the UnitedStates weather bureau in the transmis-sion of weather forecasts, storm andflood warnings and special forecasts fororchardists and bee -keepers.


Weather Controls Radio AlarmSetting Up Exercises WhenWarm - Stay in Bed When Cold

By OLIVER D, ARNOLD

T_T AVE you seen pictures of the Swiss± -I- girl clad in a bathing suit as shestands on a cake of ice about to plungeinto the freezing waters of the river?She may enjoy such cold weather butmost of us do not like to get up out ofa warm bed into the shivering air of azero temperature.

////////b ra////../////stee/COLD

long

HOT

shortFig. 1 Brass Expands with Heat

and Bends Steel

On the other hand, there is nothinglike setting up exercises to put pep intoyou for a day's work or a day's fun.And several of the big broadcasting sta-tions are now sending out music for suchexercises together with snappy descrip-tions by a physical director telling youwhen to bend your arms and flex yourlegs and how to stand on your head.Such setting up exercises over the radioare quite popular as is proven by theflood of letters of praise sent to thebroadcasting station.

But how can you combine these twoideas-that of doing fifteen minutes ex-ercise on a warm day, but sleeping thatextra time if the temperature is frigid?In the past one has had to set his alarmclock and then throw a shoe at it in thehopes of stopping the ringing, if theroom seemed cold. Furthermore, this"cold" stuff furnished a good alibi fornot getting up and doing the exercisesbut instead for rolling over and takinganother snooze. Some way was sought

which would get you up in time, if thetemperature were right, yet which other-wise would let you sleep.

The Same Old AlibiOf course, there was invented long ago

the device known as a thermostat. Ithas been used for some time in the house-hold as an oven temperature indicator.It is often used to regulate the draftsof the furnace in the cellar, so that itis not necessary to keep running downevery hour or two to open and close thedampers. The operation of such a de-vice is rather simple.

Why is Brass Like Little Girl?It depends on the fact that metals ex-

pand a small fraction of their lengthwhen they are heated and different met-als have different, rates of such expan-sion. You have all seen a little girl inhot weather stretch her arms and standon her tiptoes and yawn, while in coldweather she huddles up into as small aspace as she can. Brass does the samething-gets longer when it is hot andshorter when cold. Steel also has thesame charactericties, but in a consider-ably less degree.

It is a peculiar thing that if you al-loy steel with about 30% of nickel, thenthe resulting metal has a temperaturecoefficient (or rate of expansion) ofpractically zero. It has an invariablelength and so is called Invar. Steeltapes made of Invar are used by sur-veyors in measuring plots of land, sincewith its use it is not necessary to cor-rect for errors due to changes in tem-perature. Of course it is not at allclear why this proportion of steel andnickel is not affected by the weather, butsuch is found to be the case and in thethermostat this property is made use of.

Two Metals in StripSuppose we weld a strip of brass to a

strip of Invar, in the way shown in Fig.1. Since it consists of two parts, it is

called a bi-metallic strip. When it iscold both metals will have the samelength, as shown in the upper drawing.

John A. Spencer

Fig. 2. The Inventor of the SnapThermostat

When it is warmed up the brass expandswhile the Invar does not, as just ex-plained. Since the two pieces (brass andInvar) are welded together along theirwhole length, it is impossible for theformer to have its ends slip by the latter.However, it is now longer than its neigh-bor, so what can it do?

If you have ever seen horses or auto-mobiles run around a race track, youwill realize that the outside of the trackis longer around than the inside. Thatis why the racers all want to hug theone side, and the phrase, "the insidetrack" means that one has an advantageover his rivals. Perhaps the Invar strip

10 RADIO. PROGRESS MAY 1, 1925.

has seen a race-at any rate it seems torealize that the inside is the shorter andso the hi -metallic strip, when heated,bends into the shape shown in the bot-tom of Fig. 1. You see that the brassis now quite a bit longer than the Invaralthough the ends are still opposite eachother.

Curves Up or DownThis bending takes place more and

more as the temperature is raised. Thisis reasonable because the hotter the brassgets the more it increases its length over

EN.

when bolfomis pressed)

usual posiftonFig. 3. Snap Action is Like Bottom

of Oil Can

that of its companion. By the sametoken as the strip is cooled clown belowthe temperature at which it was flat, thebrass shrinks to a shorter length thanthe Invar and as a result it curves withthe latter on the outside.

Such a bi-metallic strip may be usedas a thermometer by fastening one endand attaching a pointer to the other.If the motion of the free end is not greatenough it may be magnified hy a systemof levers. Another use for such a stripis to open and close an electric contact.By fastening one contact to the free endof the strip and another one fixed rightbeside it the two may be made to openand close depending on the temperature.If the contact is carried on the brassside, then since the end moves towardthe brass when cold, the contact will bemade as the temperature falls. On theother hand, if the contact is soldered

on the Invar side, then rising tempera-tures will close the electric circuit.

Keeping the Room at 70°In the ordinary thermostat which works

your furnace there is a contact solderedto each side of the strip and two corre-sponding mates, one just above and theother below. When the temperature ofthe roam rises the strip bends upwardsand closes the contact which makes anelectric circuit down in your cellar. Thisoperates a device which closes the damp-ers. As the room cools down again andgets below 70 degrees, the lower contactsare closed and another contact is madewhich opens the dampers again. Thisaction is repeated indefinitely and soyour house keeps within a degree of 70all the time.

It is easy to see that such a thermo-stat will have a ve.y slow motion. Asthe room gets warmer the strip will bendupwards, but its rate of movement is soslow that you almost need a microscopein order to see its motion. That meansthat the contacts when they first touchhave such a very light pressure that theamount of current they can carry isquite small. Fortunately, only a smallfraction of an ampere is necessary towork the damper in the cellar whichcontrols the draught. Such action wouldnot do, however,. to carry the currentsfrom the "A" 'battery to operate a radioset. For such use it is necessary that aswitch be provided, which turns the cur-rent on and off with certainty and speed.

Making It SnappyUp until recently no thermostat had

ever been devised which would besnappy in its action. However, Mr. JohnA. Spencer, of Revere, Mass., Fig. 2, hasrecently invented one of these deviceswhich is so quick in its action that it push the bottom and it suddenly yieldsmay be used as a snap switch to con- with a snap, so that it takes up the posi-trol a radio set or indeed any other elec-trical device.

The principle on which the Spencerthermostat acts is so novel that it hasreceived the first basic patent on quickacting thermostatic bimetal devices thathas ever been issued by the UnitedStates Patent Office.

The story of this invention well illus-trates the old adage, "Opportunities lieseverywhere if you have but the eyes tosee them." In Mr. Spencer's case, itwas being able to apply his observationsof the action of a steam boiler which hetended years ago in a Maine lumber

camp that resulted in his recent inven-tion.

Took a Fireman's JobThe boiler was located in a lumber

mill in the northern part of Maine.Spencer, a boy about fifteen years old,was employed on the night shift in themill, and in addition to making periodi-cal tours of inspection, he had to main-tain the fire in the boiler. The task offiring kept him particularly busy as, theweather being cold, the wood refuse usedas fuel burned quickly. Therefore, heconstantly had to run to the boiler roomto see if the fire needed replenishing.

The peculiarity of this boiler lay inthe fact that it had a rounded cleanout

supporhilto rheos7671

rin7

Fig. 4. How Contact is Made by NewThermostat

door which was constantly changing itsshape with a loud snap or click. Attimes this door would be convex; then itwould snap into a concave shape; andonce again it would bulge out and be-come convex.

Try This on Your Oil CanThis same thing happens every time

you use an oil can-Fig. 3. The bottomis made so that it bulges out somewhat,normally, but when you wish to squirtsome oil on that squeaking hinge you

tion of the dotted line in the sketch.This action was well known to every

one in the mill, but no one, exceptSpencer, gave it the slightest seriousthought. The young watchman, how-ever, was interested by the action andby careful observation he soon dis-covered the cause: When the door washot, it rounded inwards; and as it be-came cool, it reversed its shape andcurved outwards. Being of a mechanicalturn of mind, Spencer rigged up a deviceby means of which a heavy log wasleaned against the door when it wasbulged in; thus he was able to engage


in other duties until the noise of thefalling log warned him that the fire waslow.

Several years ago, after Mr. Spencerhad acquired a knowledge of mechanicalprinciples, he recalled the action of theboiler door and was impressed with thefact that no one had utilized the pecu-liar action. He therefore decided to in-vestigate it in order to learn if it hadpractical value, and after a series ofexperiments, worked out a formula fora combination of metals that best suitedhis purpose.

0

11111

bafteryFig. 5. Hook-up in Set for Radio

Alarm

They Jumped Into the AirHis first practical application of the

new principle was a toy. He stampedout little convex discs which, whenheated in the hand and then placed upona cool surface, would suddenly changetheir shape with a click and spring sev-eral feet into the air.

The idea here is not to use a narrowstrip, but a round disk. After formingto shape, it is bent out like the bot-tom of an oil can as shown in Fig. 3.The brass being on the top wants to ex-pand with heat as already explained. Asthis disk is heated up the center partcannot creep up gradually as it did inthe strip, Fig. 1, as it is held as an archin the curved down position. As thetemperature keeps rising the pressurewhich it exerts increases more and moreuntil finally, at a certain degree of heat,the whole disk yields with a snap justas the oil can bottom does and it as-sumes a curve up in the opposite direc-tion.

Why the Contacts ActIf the upper edge of this disk, as

shown in Fig. 4, carries a contact, whichmates with another one on the bottomof the regulating screw, then a sharppositive contact will be made at thetemperature for which the disk is set.

The way this device is used for theradio alarm is shown in Fig. 5. Noticethat it is inserted- in series with the"A" battery. When the contacts areclosed it puts the current through thetubes' filaments in the regular way. Byinstalling the disk outside your bed-room window it will respond with musicon a warm day, but will let you sleepon a cold one. An electrical contactmade by your alarm clock times the ope-ration.

Other uses of this device have seemedso important that the WestinghouseCompany has paid a large sum of moneyto the inventor to acquire the patent.

Fast as a Rifle ShotElectrical engineers have long sought

for some effective means to regulate thetemperature of an electrically heatedappliance, such as a flat -iron, by turn-ing the current on and off automatically.Certain devices for this purpose havelong been available, but they are notentirely satisfactory, because they ope-rate so slowly that an arc forms be-tween the points and in time will cor-rode the contacts, eventually makingthem useless. When the Spencer discis used as a thermal switch, it clickson or off in less than .00018 second (aspeed comparable to that of a rifle bul-let) which is so rapid that no arc forms.Hence it can be used for heat controlwith entire success.

Westinghouse engineers state thatelectrical heating apparatus will be revo-lutionized by the use of the Spencerthermostat. An iron in which it is used,for example, will heat up to the mostefficient temperature and then with asharp click the current will be auto-matical y cut off. The iron will thenstart to cool, but before it gets too coolfor satisfactory use, the current againwill be clicked on. This process is re-peated indefinitely, so that the iron isalways kept at the proper working tem-perature and cannot get dangerouslyhot. Similarly coffee percolators, waterheaters, etc., using this device, can beboiled dry without damage, for as soonas the temperature begins to rise, thecurrent is cut off. It is also planned

to use this new thermostat on motors,generators, and other electrical machinesto prevent overheating.

COMPARING WGY AND KGO

By Martin P. Rice, Manager of Broad-casting, General Electric Co.

Radio programs are slowly but surelyimproving. The listening public is be-coming more discriminating and exact-ing.

The advertising program is beingweighed in the balance of public favorand it is doubtful if it will be accepted.More skill, art, and talent are neededto make advertising by radio successful.

Un-noising the JazzGood music is appreciated every-

where and the stations broadcasting itare always popular. Jazz still has aplace on programs, especially for danc-ing, but it is not so noisy as it usedto be and is more melodious.

Western programs include much highgrade material, but in general they lackunity. Educational programs of realvalue seem to be further advanced inthe West, particularly at KGO, thanin the East.

The radio dramas developed by WGYand carried on- by KGO and KOA al-ways bring large and appreciative re-sponses. No example of drama writtenexpressly for radio and utilizing all itspossibilities has yet appeared.

Talks Short and SnappyTalks seem to be in favor at many

stations and the studio managers arefairly successful in convincing speakersthat radio talks must be short and,above all, interesting. It is usuallyeasier to tune out than to tune in aspeaker.

The linking of several stations tomake the broadcasting of an importantpublic event available to the largest au-dience is making progress and is a realpublic service. The expense of thusconnecting stations is so high that itis not warranted except for events ofnational importance.

Wiestern audiences are more respon-sive to the request of stations for re-ports on reception. More letters andtelegrams are received by western thaneastern stations in proportion to thepopulation reached.


Exit ---Microphone FrightA Combination Mike, LoudSpeaker and Movie Screen

By VANCE

D1D you ever have an attack of stagefright? Perhaps back in your

school days you stood up on the plat-form to recite, "The Curfew Shall NotRing To -night." Sure enough, it didnot do any ringing for your tonguestuck to the roof of your mouth, andyou were unable to say a word.

Stage fright like this is bad enough,and many speakers are affected by iteven though they may have addressed,audiences many times before. But it isa strange fact that even veteran speak-ers, who can go out on the stage andface an audience of a thousand peoplewithout a tremor, will oftentimes bethrown into confusion when they stand

before a microphone to broadcast. Hereit is not the audience, but the tack ofan audience that embarrasses them.

Wanted,-A Live MicrophoneStudio directors sometimes arrange to

have a few of their friends in the roomat the time in the hope that it willmake the speaker feel more at home.It doesn't seem to have that effect,however. The trouble is that when aperson stands up before a steel drum,he can not visualize any audience andhis mind seems to rebel instinctively attalking to such an object. If some waycould be found to make the microphoneseem alive, or to represent a real audi-

Fig. 1. Explaining the Merits of the Scoreless Mike to Commander Mac-Millan

ence, it would go a long way towardsremoving the tightness in the throatwhich the broadcaster is apt to feel.

With this idea in mind there has re-cently been invented a new style whichconceals the microphone behind a screen.It is called the Micro -speaker -phone. Be-hind the grill work is a thin screenwhich allows the voice to penetrate iteasily, but which permits a movie camerato project on it. By using one of thesmall home -movie outfits, with a film ofan audience, any lecturer may be giventhe impression that he is speaking toa crowd of living human beings, insteadof a mechanical contraption.

Audience Must MoveOf course, an ordinary stereopticon

picture of a theatre could be used. Itis found by experience that a movingpicture conveys the atmosphere con-siderably better, however, as this givesthe impression of a live audience. Somepeople find it easier to address a vastthrong, while others prefer to talk to asmall group. Whichever it is, the speak-er can take his choice and insert a filmshowing the character of audience heprefers. This is found to go a longway in removing the microphone frightwhich has affected so many seasonedlecturers.

Our photograph shows CommanderDonald D. MacMillan at the left, as heinspects this new device. On the rightis seen E. F. MdDonald, Jr., who is thepresident of a National Association of,Broadcasters. He is instructing theArctic explorer as to the way the newmicrophone works. This unit is nowbeing installed at Station WJAZ, theNew Zenith studio in Chicago.

It Talks as Well as ListensAnother thing of interest in this de-

vice is the standard on which the mecha-nism is supported. Notice that thisconsists of a square tapering wooden

Continued on Page 19.


Keep Your Tubes in GoodWhy Your Neighbor's BulbsLast Twice as Long as Yours

By W. S. STANDIFORD

YOUR friend, Bill, has been runninghis vacuum tubes now for over a

year, and they are still going strong.Yours are 'beginning to get a little bitfrayed around the edges, although theyhave been in the set for a little less thansix months. What is the reason?

Various articles have appeared in themagazines concerning radio receivingoutfits using vacuum tubes for detect-ing and amplifying signals, but littlehas been published in regard to the careof these devices. Yet they are of vitalimportance in transmission work, aswell as for picking up radio concerts.

An ever increasing army of amateurwireless enthusiasts in Canada and theUnited States are constantly joiningthe ranks of those more experiencedfans in the radio field, and are to amore or less extent, ignorant as regardsthe care of radio appliances. A fewpractical pointers on the care of thismost expensive and important part oftheir receivers will enable any radiofan to enjoy the utmost satisfaction andpleasure from his outfit.

Sometihng Like Light BulbsAs detector and amplifying tubes re-

semble ordinary electric light bulbsin some ways, many amateur radiooperators who are new to the game,think that they can handle this appara-tus) with roughness of ordinary bulbs.Due to their construction, the latter aremade so as to work with their filamentsnear a white -heat, so as to obtain theutmost light possible.

This in itself makes it easier on thefilament. When the wire is at nearlywhite heat it becomes soft somethinglike the way hard rubber will softenwhen it is put into hot water. Youcan easily see that if a hard rubbercomb were dropped on a concrete floorit would be pretty apt to knock a fewteeth out. On the other hand if youhad just pulled this comb out of a boil-

ing water bath, it might bend the placewhich strikes first but owing to the factthat the material would he quite plasticit would not break.

How to Stop Its BreakingSince an ordinarY electric light bulb

runs at a temperature, which makes thefilament plastic, there is small dangerof its breaking when hot. Many yearsago when Tungsten bulbs were firstmade, the wire was very fragile andbreakage was high, even from the smalljars which were received when cleaningthe glass. For that reason the manu-facturers always used to specify thatthe current should be turned on and thebulbs lighted when any cleaning of theglass ware was to be done. This wouldprevent the filament from snapping.

The UV -200 tube has a pure Tungstenfilament, which runs at so high a tem-perature that it has something like theaction described above. But the othertubes each have some kind of coatingon the wire which gives the same elec-tron emission or plate current at amuch lower temperature and for thisreason such tubes have not the protec-tion against jars when hot that theUV -200 has.

Vacuum Tubes Don't Give LightElectric lamps are also made very

rugged in construction as compared withdetector and amplifying tubes. Thelatter are not intended as light givingapparatus, but they are much more sen-sitive for an entirely different purpose.On this account, and also because of theirhigh price and fragility, as contrasted,with ordinary light bulbs, it is best totake the utmost care of them so thatthey will have a long life.

In order to make your tubes last aslong as possible, you must keep thefilament inside at as low a temperatureas is practicable. Detector and ampli-fier tubes require that the voltage im-

Health

pressed across their filaments be kept atan exact value for best results.

When a piece of metal is heated itevaporates just the same way as waterdoes, but of course at a very much slowerrate. Perhaps you did not realize that asolid could evaporate. However, a pieceof ice, even in cold weather will slowlydisappear. The temperature may beway below the freezing point, but inspite of that, water vapor is continuallybeing given off 'from the surface of theice so that in time it will he all gone.Naturally this action is very muchslower with the cold weather, but itexists just the same.

'A' BATTERYFig. 1. Proper Way to Use Meter in

Adjusting Filament

UV -200 Much Hotter than OthersIn the same way the filament of your

tube is gradually giving off part of itssubstance, especially when it gets nearthe red hot temperature. The UV -200,as just explained, has to have such ahigh heat that it gives off electrons(which form the plate current) from thetemperature effect alone. The otherstyles of tubes, however, do not need tobe hotter than the glowing end of amatch stick to give excellent results. De-tecting and amplifying tubes requirethat the voltage impressed across their


filaments should be right, so that theymay work at their utmost efficiency andlast as long as possible.

Most people probably do not measurewith a meter the electricity supplied totheir tubes. Of those that do take areading, some use an ammeter in serieswith the filament to measure its currentand others a voltmeter to determine thevolts impressed on the tube. To meas-ure this pressure the voltmeter is con-nected as shown in Fig. 1. The phisterminal runs to the positive and theminus to the negative of the tube. If

that its resistance is higher as the tubegets old, then the voltage needed toforce this same current through thehigher, resistance will naturally begreater than what it was at the start.This increased pressure on the filamentmakes it run at a higher temperaturethan it was designed for and so the lifeis shortened.

If the voltage is kept constant on theother hand, then as the resistance goesup through old age the current will falloff slightly. However, there is now notso much filament to heat as there was

fire 9,9qe

ciusi anal dirfin lire

Fig. 2. Why Constant Pressure Beats Constant Current in PreventingDamage

the rheostat is connected in the negativeside of the battery, as is standard prac-tice, then the voltmeter will be at-tached between the rheostat and thefilament. In this position it measuresnot the pressure of the "A" battery butthat directly across the tube itself.

Volts to be Kept ConstantThe scheme of measuring the voltage

is better than that of current. Thereason is that if you keep the pressureon the filament constant throughout itslife it will work as well and last con-siderably longer than if you keep thecurrent constant. That is because thediameter of the wire is gradually re-duced as the tube is operated owing tothe evaporation of the surface as hasbeen explained. Because of the reduceddiameter the resistance goes up just asthe resistance of a pipe carrying waterincreases if it gets partially stopped upwith sediment.

If the current is kept constantthrough the wire in spite of the fact

before and so the smaller current willkeep it at the same temperature as inthe beginning. Because of this the tubewill work just as well, and yet will lastquite a bit longer.

Filament Like Auto TireTo see how this action goes on, look

at Fig. 2. Suppose we have an auto-mobile tire which we wish to keep wellinflated. We could use one of two ways.The usual idea is to put a tire gaugeon the valve and keep the pressure upto say 50 lbs. Another way would beto measure the quantity of air in thetire and keep this constant. Naturallythis would be a hard thing to measure,but it could be done. Either way wouldgive the same result as long as the tirewas new.

After it has run six months let usassume that it is partly filled with roaddust as shown in the illustration. If wekeep it inflated by the pressure method,then we shall put in the right amountof air to maintain 50 lbs. per square

inch. But if instead we measure thequantitiy, then by crowding the sameamount of air into the space which isnow considerably smaller you will easilysee that the pressure will necessarilyrun up to 60 or 70 lbs. and may causea blow out. Quite obviously the con-stant pressure method will be much su-perior. The same reasoning applies tothe vacuum tube.

A Voltmeter is Worth WhileFor this reason fans will find that a

small voltmeter (which is an instrumentfor ascertaining the amount of pressure,or voltage) will save them its cost manytimes over in prolonging the life of thetubes. 'Indeed, it is one of the best in-vestments that any person interested inradio work can make. It also comes inhandy for finding out the strength ofnew dry batteries when purchased, assome of those that have stood on dealersshelves for sometime, may be weak inpressure.

For testing dry cells an ammeter isslightly better than a voltmeter, as thereading changes more with increasingage than is the case when a voltmeteris used. The latter instrument, how-ever, while not quite so accurate willpick out old or used cells very easily.When new, a dry cell has a pressure of11/2 volts. This gradually drops off asit is used until when it has fallen toone -volt it should be thrown away.

When Detector is Not AmplifierMany broadcast listeners think that

a detector and an amplifier tube arethe same thing. This is true about allthe styles except the UV -200, which canbe used as a detector only. It is prob-ably the most sensitive device made forthis purpose. It will not work well,however, as an amplifier. All the othertubes may be employed equally well asdetector or amplifier.

The chief difference between the UV -200 detector and the other tubes is theamount of vacuum. The former has asmall quantity of gas run in after ahigh vacuum has been formed while theother tubes are sealed off at the highestexhaustion which the vacuum pump willgive. It is termed a "soft" tube as con-trasted with an amplifying one, called"hard." As a matter of fact, either typeaf tube may be used for detector. Butan amplifier is best suited for amplifica-tion use as it is specially designed for


that purpose. Such a tube has a highervacuum and on this account, it can usea higher voltage "B" battery.

A Poor Way to Tune InSome amateurs try to get distant sta-

tions by tuning more current into theirtubes, thus heating the filament hotterthan it is intended to be. This is a dan-gerous practice and it shortens a tube'slife. It will readily be seem from theabove, that a person having a three orfour tube radio set has a neat sum ofmoney invested in tubes alone, so as itis advisable from a financial standpointto make them last as long as possible,and not try any experiments in extra -hot filament heating so as to cause dis-tant stations to come in louder.

It is hardly necessary to add, thatonly inexperienced amateurs overheattheir tubes. But large numbers of themare making and purchasing outfits, whonaturally know very little about the insand outs of radio, so this informationis timely and will save them money.Another pointer; a vacuum tube afterit has been in use a certain length oftime, say about three months, may be-come either softer or harder than be-fore, the matter depending upon con-structional factors that vary. Thiscauses a radio novice to blame the manu-facturer for marketing an inferior ar-ticle, which is not the case. All makersare doing their utmost to get theirproduct as uniform in quality as possi-ble.

Sometimes a tube that has changedits hardness after several month'susage, will become noisy, and while localstations can be heard, out-of-town broad-casts will not be received very well. Ifboth the "A" and "B" batteries testhigh and are in good condition, it ismost likely that a tube has changed.You will want to find out whether suchis the case, or the fault is with someother part of your set. It is a goodplan for a radio enthusiast to try outany tube which refuses to work wellin a friend's set-one that is operatingsatisfactorily. By doing so, you willthen be able to tell the condition of yourtube.

If it is a hard tube, more "B" batteryvoltage may be used in order to makeit operate best. Should it prove to be"soft," use lower potentials so as to en-able it to work well. A few experimentsalong the above lines will save many

a tube supposed to be defective from be-ing discarded when it apparently re-fuses to give good service. The writerran across an interesting case sometimeago. An amateur had a new WD -11tube, which failed to operate after us-ing it three hours per day, for a periodof three weeks. As it would not workeven with the rheostat arm turned awayround to "on", he concluded that it wasburned out and was about to discardit and buy a new one.

Where the Trouble LaysI suggested that he test the tube by

removing it from its socket and con -meeting the two filament prongs acrossthe terminals of a single dry cell. Whenthis was done it lighted up brilliantly.The fault was found to be in the rheo-stat contact arm, as it had been bent upslightly and was not in contact withits resistance wire (See Fig. 3.) Whenthe switch arm was bent down again soas to press against these wires firmly,all trouble vanished.

Fig. 3. This Explains a FrequentCause of "Static"

Some radio fans do not like a wire -wound type of rheostat, but prefer thecarbon disc style, as they think that itgives less trouble. As a matter of fact,both give excellent service in radiowork if they are well made. As rheo-stats play such an important part intube current regulation, it will be ofinterest to the ever increasing armyof novices to know what to look forwhen they purchase rheostats so as toobtain the very best-it being an axiomthat a high-grade article gives the leasttrouble; this applies with double forceto radio parts owing to the rapid way,the art is advancing at the present time.

Picking a Good RheostatA first-class wire -wound rheostat

should have the following characteris-tics: Its wire ought to be tightly woundin place so as to prevent any looseningof its coils during expansion and contraction. The wire should be of suffi-cient thickness so as not to get too hotwhile carrying the current. A rheostatto work with a UV -200 will be requiredto carry one ampere, while the unitcontrolling a single UV -199 takes but1/16th of an ampere. That explains whythe wire for the two different capacitiesof rheostat must be of such differentdiameters.

The contact arm should be made insuch a manner that its pressure on thewire coils can be adjusted. In order toreduce wear to the lowest possible ex-tent, hard phosphor bronzefor contactarm's is better than brass. All wiresought to be spaced as closely as practic-able. Close wires coupled with a widecontact arm give a more sensitiveadjustment and prevent a tube fromflickering. The switch arm knob shouldbe firmly fastened so as not to workloose. The resistance wire must fittightly in its groove, and lastly, the in-sulating base of the rheostat should beaide to withstand the heat given off bythe wires without softening.

Buying Cheap JunkSometime ago, I thought that I would

try out a rheostat bought in a cut pricestore; the cost was ten cents per partor thirty cents in all. It didn't givegood satisfaction, being too badly andloosely constructed and got out of orderquickly. It was soon discarded, a wasteof money resulting; but as my objectwas to find out what kind of radiomaterial is sold in those stores. I wassatisfied with my experiment.

Another pointer; do not leave yourrheostat (which controls the tube's heatrange) set at the same position when itwas last used and expect it to heat thefilament to the same degree of rednesswhen you listen -in on the followingnight. It will be found that you mayhave to alter its resistance in order tokeep a tube's brilliancy at the properpoint. There are two reasons for this.In the first place a battery which is part-ly run down will have its voltage lowerthan normal owing to this use. Afterstanding for some hours it partially re-gains the pressure that was lost. If


you keep a volt meter connected up toa battery after snapping off the filamentswitch, you will find that it may riseas much as ten percent. by the next day.For this.reason the pressure on the fila-ment will be too high and so the rheo-stat should be turned farther toward the"off" position when starting up the tube.

The second reason for this shift is thatall metals when hot have a higher re-sistance than when cold. This appliesnot only to the rheostat wire, but also

adjusted if so desired, is shown in Fig. 4.Due to its construction, this detectorcannot be thrown out of contact with thegalena or other mineral nor will its ac-tion stop if the point of the wire isburnt off, as sometimes is the case withthe ordinary pattern. Instead of touch-ing the crystal at one place the wirebears against it at numerous spots;there are plenty of sensitive grainspressing against it. Any vibration oc-curring simply shifts this wire to differ-

ISSMINNIMINSIMINNIMMINIMMI

Witt.4',A.1%*4\Te.0.41.0;1V..;Mtv,%V.4:4

Fig. 4. A Crystal Detector That is Especially Suited to a Reflex

the rest of the circuit. The rheostatwas adjusted the night before after theentire circuit had been warmed up by acouple of hours current flow, and owingto the higher resistance of all the partsthe rheostat was set at a loweri value thanwill be needed the next day when every-thing starts cold again. This againmeans that the rheostat should beturned around slightly when starting topick up a program. Of course, neitherof these causes is very serious but ifthe longest life of the tubes is desired,these points should be looked after.

The usual type of crystal devices inuse on reflex radio outfits has somedrawbacks, which prove to be very an-noying when a person is listening -into a broadcast concert. The cat -whis-ker wire on these detectors has thedisadvantage that the slightest vibrationis apt to throw its point off the sensi-tive galena spot and so stop receptionin the midst of an interesting program.In most cases, it takes a lot of time andpatience to find another sensitive place,and thus a good part of an entertain-ment is wasted.

A type of crystal detector which' doesnot have this disadvantage, but can be

cnt grains. So much for its advantages;now for constructional details.

Building the DetectorProcure a piece of Bakelite or other

high-grade insulating panel 3/16 inchthick, 2% inches long by 11/2 incheswide; one piece of copper tube one inchlong by 3/8 inch inside diameter; asmall piece of sheet copper about 1/16inch thick and 114 inches square; twobinding posts and some round -head woodscrews of suitable size.

Solder the tube to the sheet of copper(Fig. 4), making holes for the bindingposts, also for the screws to hold it up-right. Two other screw holes should bemade in the insulating base so that itcan be fastened down. Get a number 20or 22 guage piece of phosphor -bronzespring wire and make a loop in its cen-ter as shown; the object of this loop isto keep the "eat -whisker" thrust downinto the galena grains. Cut your wireso that when it is placed under the bind-ing post, it will occupy the center of thetube, extending within 1/4 inch of its bot-tom. Both the inside of the tube andalso part of wire projecting into it,ought to be brightened with fine sand-paper, taking care not to touch either

surfaces with your fingers, or get anyoil in the inside of tube or on the out-side part of the wire.

Untouched by Human HandsPulverize enough galena crystals to

fill the pipe within 1/16 inch of its top.Don't make it too fine or touch it withyour fingers either before or after pound-ing. Handle it with a clean piece ofpaper. Fill it by creasing a stiff pieceof writing paper, pushing the grains onit with a clean stick, after which thetube can be filled by gradually slantingthe paper and pushing the material intoit with the stick.

Under no circumstances whatevershould these crystals be touched by thefingers as there is sufficient natural oilon the skin to stop the reception of mu-sic or code signals. Place your bindingposts in position as illustrated, and con-nect this appliance to your set in placeof the regular one and it is ready foruse. You will be surprised to note howthis type of detector retains sufficientcontact between many sensitive galenaspots, thus enabling a steady receptionto be maintained during vibrationscaused by a heavy motor car shaking thehouse, or by a person walking across thefloor.

How to Clean Your Old CrystalIf a radio enthusiast has a number of

dirty galena crystals, he can clean themby immersion in alcohol. Use medicated,not the denatured article. An old toothbrush gives good service taking care notto touch the crystals with the fingers.Handle with tweezers after cleaning.Then pound them up and fill the detectortube. This will save the expense ofbuying new ones, and they will be foundto give as good service as new crystals.Let the galena dry before putting it inthe tube, if it has been cleaned withalcohol, as verdigris may form and stopreception.

CONNECTICUT ON ITS EAR

A bill has been introduced in the legis-lature of Connecticut to prohibit "emit-ting any noise or other disturbancewhich deliberately interferes with broad-casting of concerts and other programsbetween the hours of 6 p. m. and 12 p. m."


Latour's Patents Control RadioWhy Many Big Companiesare Taking Out His Licenses

An Interview from DR. 0. C. MAILLOUX, Honorary Presidentof International Electrotechnical Commission

THE smoke has not yet cleared fromthe battle between the Westing-

house Company and the DeForest Com-pany over the regeneration patents. Youwill remember that Major Armstrong as-signed his invention to the Westing-house Company, while DeForest turnedhis over to the Company bearing hisown name.

Now more patent trouble apparentlyis coming, as it appears that many ofthe basic ideas which practically everyradio set contains were developed} andpatented by a French professor. It isonly recently that Prof. Marius C. A.Latour has started the active pushingof his inventions.

Latour himself is quite modest andnot given to self advertisement; that isprobably why he is not so well knownon this side of the Atlantic. But it isto the genius of this man that is duethe delight of millions of our citizensin radio broadcasting, which is to -day sotremendous a factor in the entertain-ment and instruction of people all overthe world.

Well Known AbroadLong before the war, Prof Latour had

already attained the summit of distinc-tion in electrical engineering and inven-tion, not only in France, but in allEurope. This gives an idea of the quali-fications of the man for the task of de-velopment in inventions which was in-

SaccoNI DARYPR6iip,Ry

RON CoRE--"1/4

Fig. 1. Shows Principle of Iron -Cored Transformer

trusted to him as a result of the war.The radio inventions of Prof Latour

are now attracting world-wide attention,pa}rticularly here in Ameripa, Whereradio broadcasting has become a factorin the everyday lives of all of us. Theyare the results of research work begunby him long before the war and broughtto complete development and utilizationduring and as a result of the war. Itwas, indeed, because of his early re -

when I had occasion to meet him inFrance, I learned for the first time ofhis interesting results in receiving sig-}nals from very distant stations withoutany antenna and with the extremelycompact apparatus developed by him.

This apparatus was the basis of thatwhich was put at the disposal of theAllies for radio reception. Models weresent to this country to be copied for theuse of our own army and navy.

Fig. 2. This Invention Saves a Lot of "B" Batteries

searches with reference to methods ofsecuring amplification of weak currentsthat, at the outbreak of the World War,the governments of France and of theAllies looked to Prof. Latour to con-tinue his intensive studies. Additionalresearch in the development of his earli-er ideas enabled the Allies to take lead-ership in the field of radio reception.

The First Meeting in FranceHis intensive work enabled him to ob-

tain results that seemed extraordinaryin the early part of the war. In 1916,

Mr. Latour's inventions undoubtedlypreceded all other methods of radio re-ception with amplification. They arethe basis of all present systems for thereception of code signals. They are infact, the underlying foundation of thepresent system of radio broadcasting.

Out of the vast mine of ideas and dis-coveries which he opened up, came theinventions made by him and others,which are now being used in broadcastreception.


Is Yours an Infringement?Professor Latour himself states that

every receiving set used in America, byamateur radio operators and by broad-cast listeners, is a violation of hispatents, granted and pending. Such setshave been and are being manufacturedby scores of companies taking advan-

Fig. 3. It is the Taps on This Vario-coupler That Count

tage of the tremendous demand for re-ceivers.

It is contended by the Professor thathis inventions, dating back many yearsand coming before broadcasting becameso popular, are so broad and coverradio art so well that it is practicallyimpossible to build a receiver in thepresent state of the art without in-fringing on one or more of his inven-tions.

It is not going too far to say that thesuccessful research work of ProfessorLatour, in the field of radio, before andduring the war, was the starting pointof the development which made Ameri-can broadcasting what it is to -day, forhis inventions have contributed as muchto broadcast sending as to reception.The finest broadcasting stations in theworld are in fact equipped with Mr.Latour's sending apparatus, inventedand perfected by him.

For 11 Years with G. E.Professor Latour was !for eleven years

a consulting engineer to the GeneralElectric Company. He has been con-sulting engineer to several of the largeelectrical companies of Europe. Allbroadcasting stations in France werebuilt under his patents for transmittingapparatus, which is also used in othergreat stations of the continent. He isthe inventor of big frequency alterna-tors, frequency multiplies, as used in

the Sainte Assise, Lafayette Belgradeand, Coltano radio stations of France,and magnetic modulators for any wave-length, as used in the Paris station. Hehas many inventions in dynamo -electricmachinery and the like.

He is now professor at the EcoleSuperieure d' Electricite in Paris andis continuing research work, his hobby,along with writing books on poetry andphilosophy. One of 'his books is "ThePhilosophy of the Emotion."

Within the radio industry there hasbeen naturally considerable fear as tothe effect of this situation. Manufac-turers, distributors and dealers haverealized that any apparatus handled bythem, which infringes valid patentsmakes them liable, under law, for allthe profits accrued through the sale ofsuch infringing devices or for tripledamages suffered 'by the parties con-trolling the patents. If such claimswere pressed for adjudication by thecourts, the amount involved wouldprobably run up into many millions ofdollars.

Professor Latour explained that thefollowing features of construction anddesign in radio receivers involve in-fringements of his inventions.

The Iron -cored TransformerAudio frequency transformers which

use an iron core. This is represented inFig. 1 which shows that the iron actsas a spool on which the primary andsecondary turns are both wound. Sucha core gives maximum amplificationwithout the bad effect of distortion. Allradio sets which have one or two stepsof audio use this idea.

Radio frequency transformlers withan iron core. Such units are manu-factured by some concerns but themajority use air cores and so do notcome under this patent.

;Rico

A"

"B` BATTERY

Rums:

Fig. 4. A Simple Way of Using ThisInvention in a Set

Using a single "B" battery for sev-eral tubes. This is illustrated in Fig.2. At the top is shown the ordinarymethod of connection with a single "B"battery which is common to every bulbin the set. At the bottom of Fig. 2 isshown the scheme of connections with aseparate "B" for each of the varioustubes. This used to be the way setswere hooked up until Latour patentedthis improvement.

Variocoupler Comes NextThe tapped coil. This is a very popu-

lar way of changing the wave frequencyin the ordinary set. It usually takes theform of a variocoupler. Such a unitis shown in Fig. 3. Notice the tapswhich are connected to a tap switchin such a way that one or another maybe picked out depending on the wave

Fig. 5. The Polentiometer PreventsRadio Frequency Tubes from Osci-lating

frequency. A simple way of connectingsuch a tapped coil appears in Fig. 4,where the taps are used to get coarsetuning while fine adjustments are madewith the 23 -plate condenser.

The method of preventing radio fre-quency tubes from breaking into oscilla-tions by use of a potentiometer. Fig. 5shows a simple hook up of one tube ofradio frequency amplification feedingthe detector. The potentiometer isshown at "P." Notice that by adjustingthis unit a variable voltage is im-pressed through the tap switch andcoil "E" on the grid "G". By giving thisthe proper voltage bias, any self os-cillation of the amplifier tube can beprevented.

Destroying Hand CapacityGrounding the filaments or "A" bat-

tery. In Fig. 6, which shows a Neu-trodyne hook up, notice the connectionin the lower left hand corner betweenthe ground wire and the "A"- lead.This connection is not necessary for


the operation of the set. However, ithas a distinct advantage for two rea-sons. In the first place it tends toprevent unwanted oscillations in thefirst two tubes and besides that it re-duces body capacity to a very large ex-tent. Every radio set should make useof this connection.

In view of these basic patents it isn'tsuprising that Prof. Latour is now get-ting after the radio industry to pay him

a royalty for their use. As he is awealthy man, he is not making any at-tempt to collect back damages or pro-fits. This is fortunate for the manu-facturers who have been using his in-ventions. However, he has sold licensesto at least four of, the largest manu-facturers to make use of his eightypatents.

The purchase of these licenses by theAmerican Telephone & Telegraph Com-

pany, the Radio Corporation of America,the Postal Telegraph Company and theFreed-Eisemann Radio Corporation, ac-cording to a statement made on au-thority of the last named organization,is a concession of the validity of thepatents, in the first place and, in thesecond place, gives these companiesabsolute manufacturing and sellingrights.

8+5 -I.0B90+

A 6 -

Fig. 6. Notice in the Left-hand Lower Corner the Connection from Ground to Filament Line. This Reduces BodyCapacity

EXIT-MICROPHONE FRIGHTContinued from Page 12.

pedestal. It is in fact, a large organpipe. At the bottom of the column isinstalled a loud speaker telephone unit.In this way the apparatus may be usedas a loud speaker to receive broadcast-ing from some other station or as atransmitter to do its own broadcasting.

By combining the two functions, it ispossible to change a solo into a duet.If some sister station is broadcastingthe air of a popular song by a wellknown soprano, this can be tuned in onthe loud speaker. If a tenor stands be -for the combined unit, he can hear thetones as brought in, and at the sametime sing an accompaniment to it. Of

course, the microphone, which is in-cluded in the upper part, will pick upthe harmony from both loud speaker andsinger, and so the music broadcast fromthe studio will be a duet.

JAZZING THE TOBACCORadio music speeds up work and hur-

ries on the workers. This idea is in linewith the thought that music is helpfulto digestion at meal -time. Yet con-firmation of the first -mentioned theorycomes from a Kentucky township, wherethe chief industry is tobacco growing.One of the "gang" bosses of the pro-gressive type thought of furnishing musicwhile his workers were tying tobacco,and he tuned in for one of the dance or-chestras, whose concerts are regularlybroadcast by Westinghouse Station WBZat Springfield, Mass., from its Bostonstudio. The tobacco was tied in recordtime, nobody seemed tired, and many ofthe group went rabbit hunting the nextmorning at sunrise.

Six hundred pounds of tobacco of thePittsylvania bright leaf were tied upquicker than ever before. When theworkers started, the thoughts of the

next day's rabbit hunt was disturbingthem. The piles of leaf tobacco ap-peared unusually large and it did notlook as if many rabbits would be chasedthe next morning. The radio was turnedon, and the jazz band started its tunefulselections. More tobacco was tied inDanville that night than ever before.

The nimble fingers of the tobaccoworkers never had tied so rapidly andsecurely before. The jazz music was theinspiration. One of the older tenantsaffirmed that years ago he had workedto the music of fiddle and banjo withsome degree of success, but that as astimulating and energizing factor,theradio had them all beaten.

MAINE TO CALIFORNIAOne hour a day of a national radio

program, interconnected over the wholecountry under some independent direc-tion, has been suggested by HerbertHoover.


Distortion a Good Thing ---SometimesWhat Ruins An AmplifierMust Be Had by a Detector

By DR. PETER I. WOLD, Professor of Physics, Union College

NEXT to "low loss" the most talkedof word nowadays is probably "dis-

tortion." We all know that when themusic comes in rather poorly and thebroadcasting singer's voice seems tohave an attack of gout, then our friendsput on a learned look and murmur "dis-tortion." But what does this termmean and is it always a disadvantage?

In these days all of us have becomeso well acquainted with vacuum tubesthrough actual use, or through thecountless articles on radio sets makinguse of them that anything further mightalmost seem superfluous. On the other

Fig. 1,. Two -Stand Vacuum Tubes-Detectors or Amplifiers

hand, there may be some who have onlyrecently become radio fans; or it maybe that the exceedingly versatile device,very commonly called a vacuum tube,(Fig. 1) offers some points of viewwhich may be new to many.

Tubes Do Six ThingsIf you have followed the radio art

very long, you will have heard of thesetubes being used in a number of differ-ent ways,-as for audio frequency am-plification, radio frequency amplifica-tion, detection, regeneration, and oscil-

lation, any or all of these occurring inyour receiving sets; and if your interestcarries over to the ,broadcasting stationas well, you have heard in addition, ofoscillation generators and of modulation.

One of the simplest circuits showinga tube detector appears in Fig. 2. Theaerial excites the coil, which is tuned tothe incoming wave frequency. The gridcondenser conveys the oscillations to thegrid and the output of the plate flowsthrough the phones to the "B" battery.Fig. 3 shows an amplifier reduced toits lowest terms. The input applied tothe transformer primary, is carried bythe secondary terminals to the grid andthe output from the plate works theloud speaker. Notice particularly thatwhereas the detector uses a grid con-denser, the amplifier never does.

Repeating or DistortingAll of these various terms may sug-

gest a confusing variety of uses for thevacuum tube, but it may simplifymatters in your mind if it is pointedout that this tube has really only twofunctions, which are separate and dis-tinct, and all the various uses justmentioned come under the one or theother. These two functions may bespoken of as the repeating action andthe distorting function. The two are

A BAIA I.

Oa lo Cord,.

Fig. 2. This is a Very Simple De-tector Circuit

present in every tube in an amount de-pending on its design, i. e., the relativesizes and spacing of the elements (grid,plate, and filament) in the tube, amountof vacuum, etc. By the way in whichthe bulb is operated, and by the circuitwith which it is associated, the one orthe other of these two characteristicsmay be emphasized.

IN PUT OUTPUT

PR I. -1,1,1+0Src.

Fig. 3. No Amplifier Hook-up Couldbe Simpler

By the first of these functions, Imean that of repeating the electricalvariations or waves in the output, whichhave been impressed on the grid. Ofcourse, the amplitude (loudness) of therepeated waves, must be considerablygreater than that of the input, or elsethe amplifier is not doing much good.An increase in volume of 5 to 2l timesis not unusual. The output waveshould be a faithful reproduction of theinput. See Fig. 4.

The second function I refer to is thatproperty of the tube by which inputvariations on the grid result in outputvariations, generally amplified, whichare substantially different, Fig. 5. Asan example of the first we may takethe relaying of telephone messagesacross a transcontinental line in whichthe greatest precautions are taken tomake the repeating action as faithfulas possible, i. e., to reduce distortion toa minimum.

When Your Friend Hangs UpWhen you talk from New York to

California you naturally want yourfriend to say, "Why, yes, old scout, I


recognized your voice right away." Butif the amplifier has a tone of its own(distortion) he may think your voicesounds like that of a creditor and hangup the receiver.

Fig. 4 makes this action plainer. Theupper line shows a complicated wavewhich is impressed on the grid of theamplifier. It consists of a high radiofrequency or carrier wave, which has

eV,

Fig. 4. What an

41.:111.1t0

tube can not leave any out. The shape,however, is quite different. Owing tothe intentional distorting action of thetube, the high frequency vibrations runabove the zero line considerably morethan they drop below it, The dottedline which is drawn through the centerof the high frequency vibrations, rep-resents the average current, and it isthis average which operates the dia-

"stArdifAmplifier Does to Incoming Radio Waves. Shape is the

Same

been modulated into groups at a lowfrequency, or audio tone. There arefour such audio vibrations illustrated.The lower curve of Fig. 4 shows thesame wave as it corn -es from the outputof the grid. Notice that the number ofvibrations is exactly the same and thegeneral shape has not been changed.The volume, or amplitude, which is rep-resented by the distance up and downis considerably greater than before, andthis represents the amplification or gainin loudness, which the tube has given.If the shape of the lower curve did notlook like that of the upper, you wouldknow that distortion had occurred.

As an example of the second, we maytake the detection of a radio message inwhich electrical oscillations or varia-tions of perhaps a million cycles-andtherefore quite inaudible-are so dis-torted or converted as to give oscilla-tions of an audible frequency at say1000 cycles (1 kc ), which correspondsclosely to the note high "C", as playedon a piano.

Cutting 1,000,000 to 1,000Fig. 5 brings out this point. The

upper curve here shows the input to thedetector, tube. Let us assume that itis just the same as the output of Fig.4. In other words, the radio amplifierstep of Fig. 4 feeds directly to the de-tector of Fig 5. Now notice the lowercurve. Of course, the number of vi -1 stions must be the same, since the

phragm of the phones. Notice that thevibration speed of this dotted line is re-duced from one million down to onethousand oscillations per second, whichalready explained, corresponds to high"C." In this way the note which thesoprano sing into the microphone atthe sending studio, has come out justthe same in the phones at your home.

Detection is Most InterestingThe repeating action of the tube and

its circuit, with amplification, wouldprobably be held to be the more im-

fifLoci,

-/aao kc

ment which is raised to a high tempera-ture by the current of the "A" battery,whereupon it gives off electrons-thosesmallest particles of matter or electri-city which we have come to recognizeas playing so important a part in allour affairs. Then there is a plate keptat a positive potential by the "B" bat-tery, and' which therefore attracts thenegative electrons from the filament,thus giving rise to an electric currentto the plate. Finally, there is the gridplaced between the two. When the gridis made more positive, a larger currentflows from the filament to the plate andthrough its circuit, and when it 'be-

comes more negative a smaller currentflows. It is possible thus to control theplate current by 'changing the potentialof the grid. The important point isthat the input energy (Fig. 3) for ex-ercising this control is very much lessthan the output energy of the 'controlledcurrent. It is for this reason that thedevice acts as an amplifier.

Drawing the Characteristic CurveThis will be plainer if we draw a

diagram of the way the tube acts. Inthe curve Fig. 7, let the distance backand forth represent the voltage as mea-sured between the grid and the filament.Distances to the left mean that the gristis negative, while going to the right itis positive. Up and down represents theoutput from the plate, as measured by amillameter in the "B' battery circuit.

a

Ike

Jv

Fig 5. How the Detector Treats the Amplified Waves of Fig. 4. Noticethe Shape is Changed

portant property, for it includes suchapplications as long distance telephonyand all the actions in radio work men-tioned above except that of detectionand modulation. On the other hand,its quality as a distortion device is themore interesting, though not so general-ly understood.

Let me remind you for a moment ofthe essential elements of the standardvacuum tube, Fig. 6. There is a fila-

The higher up we go from the bottomline, the stronger it shows is the output.

When the grid is made quite negative,the plate current is practically zero.This is shown by the start of the curveat the left hand end. Notice that thisis practically down to the zero line. Asthe pressure on the grid is increasedmore and more, the output from theplate picks up at the same time. Atfirst the output increases at a good deal


greater rate than the input. This changein its rate of growth is indicated bythe fact that the line is curved.

When it is SaturatedWe next come to a section where the

line is straight. That means that aswe keep making the potential on thegrid stronger and stronger, the output

Fig. 6. The Necessary Parts Inside aTube-Three Elements

goes up in the same proportion. Nearthe top of the line it becomes curvedagain, which shows that beyond a cer-tain positive value of the grid, theplate current can not increase verymuch. That is the so-called "satura-tion current" of the tube.

An amplifier circuit is designed sothat the tube works along the straightpart of this characteristic line. Since,as just explained, the variation in out-put is proportional to that of input,you can readily see that a radio wavelike the top of Fig. 4, will cause thesame shape of output as shown at thebottom of Fig. 4. On the other hand,it does not require any mathematics foryou to grasp the idea that if the tubeis so adjusted that it works on thecurved part of the characteristics ateither the top or the bottom of the line,the output will not follow the inputvery exactly.

The curvature of the "characteristic"depends on the design of the tube and, inany given tube, may be emphasized bythe circuit with which it is associated.

What the Grid Condenser DoesThe big aim in life of a grid condenser

is to increase this distortion or curva-ture of the line as shown near the bot-tom of Fig. 7. When the proper valueof grid capacity-usually about .00025mfd.-and the ;proper 'grid leak arehooked up to the grid of a detector tube,then the operation will be right in themiddle of this curved portion and thedistortion which is wanted will be

greatest.Suppose we have a tube circuit which

has a curvature (detector) and we im-press on the grid two electric currentsof different frequencies at the sametime. It can be proved in theory and isfound by experiment that there are pres-ent in the plate circuit four different vi-bration speeds combined together- (1)the high frequency; (2) the low !fre-quency; ,(3) high minus low; (4) highplus low. In other words, the resultantcurrent is not a faithful reproduction ofthe original impulses, but shows somedistortion.

Modulating a Million CyclesThis is a very useful thing, as may

be seen if we apply the principle to abroadcasting station. Suppose, for ex-ample, that we combine in a tube cir-cuit the radio frequency of one millioncycles (300 meters) with a musical vi-bration speed of one thousand cycles.Then, in accordance with what was saidabove, we would have set up in the

is of. too low frequency to affect theradiating antenna of the station, but theother three, being of suitable high fre-quency, would be radiated.

It is these three waves of slightlydifferent vibration speeds which wouldtravel out to your receiving set. Themiddle one of these, one million, iscalled the "carrier wave," and theothers are named the upper and thelower side waves, or "side bands." Thethree together constitute the modulatedwave, i. e., the wave on which has beenimpressed the message which is to betransmitted. The side waves or fre-quencies are the important ones and itshould be noted that they were not ori-ginally present, but were brought inonly by the distorting effect of thetube. The mixture of the original fre-quencies is a very intimate one.

Working the Modulation BackwardLet us now go to the receiving set

where these waves are picked up. Theyfinally reach your vacuum tube. If thistube is a RF. amplifier, and so showsno curvature or distortion, it willmerely repeat and amplify the highfrequency waves which arrived, butthese, in that form, are of no use, forthey vibrate so fast that they are in-audible. What is desired is a musicaltone of the same as thel original fre-quency, i. e., one thousand, or high C."Obviously it is going to take somethingradical to get this from three frequen-cies, each at or in the neighborhood of

Co?'" E-1?0CURRENT.LINE

INPUT To GRID +

Fig. 7 This is the Curve Which Showas How a Tube Acts

plate circuit the original, and also thesum and difference frequencies, i. e. wewould have in the plate circuit speeds of1000; 1,000,000; 1,000,000 plus 1,000, or1,001,000; and 1,000,000 minus 1,000,or 999,000. The first of, these, 1,000,

one million. Suppose, however, the tubeand its circuit has its distortion, thenby the same principle as given before,there will appear in the plate circuitcurrents which are the same as the

Continued on Page 26

FOOLING OLD MAN STATICIf some one asked you for a

six -letter word meaning a lot ofweird noises from your loudspeaker, you would probably beable to tell him the answer inpretty short order. Ever sinceradio was first sprung upon anastonished world, the great prob-lem, especially of the summertime, has been to cut down thetrouble from static.

There have been various de-vices on the market from time totime which are claimed to get ridof this interference. So far, noneof them have been very practical.Of course, as a general proposi-tion, a good set is not botheredas much as a poor one. This canhe seen if you consider that onekind of a noise is like another, asfar as your set knows. We havenever yet run across a radiowhich might be said to have amusical ear. In fact, they arejust as willing to bring in a seriesof discords as they are the finestmelodies.

Two Ways of ControlRemember that there are only

two ways of separating soundswhich are known to science. Thefirst of these is that of tuning tothe particular frequency (wavelength) of the vibration which iswanted. Such tuning allows thiswave to come in with fullstrength, while it reduces allother vibrations in proportion asthey are more or less separatedfrom the frequency you want.The other way is that of direc-tional reception. When using aloop it is possible to turn it sothat waves arriving along someone line are suppressed. Thosecoming from other directions arebrought in more or less loudly,

depending on how far they di-verge from the line of the coil.

Of course the great majority ofsets do not use such a loop, andso 'this second method of pickingout what waves you want can notbe used. That is the big advan-tage of the loop set-it can selectits program ; first of all, by tun-ing, and second, by aiming theloop.

Static is Invited, TooHowever, after you have tuned

your set to the vibration speedyou want, and then aimed it inthe direction you wish, you havedone all you can in the way ofcutting out undesired vibrations.If your favorite station is puttinga wonderful program on the air,of course it will come in withsplendid effect. But if at thesame time the forces of natureare letting loose a lot of staticat the same frequency and in anydirection except the one line fromwhich waves are suppressed, thenthe static will come in equallywell.

Another thing which makes ithard to get rid of this unwelcomedvisitor, is that while a broadcastingstation builds up its energy by alarge number of tiny vibrationswhich may be tuned pretty ex-actly, on the other hand, statichas only a small number of waveseach of which is quite large.Owing to the small number ofvibrations, it is impossible to tunevery sharply against them.

Tuning Two ClocksIt is like two clocks ticking on

the mantelpiece. If you listen tothem'both at once for a few ticksit is hard to say whether they aregoing to keep in step or not. But

if you listen over a period of sev-eral minutes, you will usually findthat although they may startboth ticking at the same time,they will gradually pull out ofstep and then in again, and keepthis action up indefinitely. Inother words, it is possible totune them together over a largenumber of ticks (vibrations), butif only a few are taken, the tun-ing will be very broad.

It is owing to the fact that theenergy of static is all gatheredinto a few big waves, rather thanspread out over a large number oftiny ones, that makes it so hardto get rid of it even in a goodset. But selectivity helps somewhateven at that. Just as a good setwill pick up the frequency youtune for, and reject another sta-tion which is ten or twenty kilo-cycles away, so the selective setwill be able to suppress a gooddeal more of the outside noise bytuning than it will if it can notseparate such! stations. Rightaway that points to the fact thatyou should never use a single -circuit set in the summer time.In that respect it resembles thespring, fall and winter. Everysingle -circuit squealer should bemade over so as to use a separateaerial and grid coil, in this waysharpening your selectivity, de-creasing static, and stopping thesqueals which otherwise annoyyour neighbors.

Increasing the PowerWhen all this is said and done,

the fact still remains that one isapt to be bothered by static tosome extent. What is the nextstep to reduce this interference?To tell the truth, there is nothing


more that the broadcast listenercan do to his own set to improveresults. The sending station isthe next place of attack. If thebroadcaster increases his power,then static appears to fade in thesame proportion.

As an example of this, remem-ber the time you were getting1500 miles on a single tube. Withthe ear phones clamped on tight,it was a strain to catch the mysticwords which would tell wherethe sending station was located.Just at that moment someonerattled the newspaper and the callletters were lost. That news-paper rattle was just the sameidea as static. Ten minuteslater, after you had triumphantlylocated the DX station, youswitched back to your local sta-tion and heard them come pound-ing in. Now the newspapercould be rattled at a great ratewithout causing any disturbance.Why? Merely because the amountof power coming in was now agreat deal more than it had beenat the time static caused thetrouble.

Loudness Not Whole ThingIt is a well-known fact among

those who have experimentedthat loudness alone does not countso much in hearing clearly, as doesratio of sounds. Thus in a quietroom we can easily hear a wordspoken in the lowest tones, whereasthe same person shouting in a boilerfactory can scarcely be understoodabove a deafening din.

When considerable noise isgoing on in the room you posi-tively can not hear a clock tickat all, and yet the same clockkeeps you awake at night in yourquiet bedroom. That is, it is therelative amount of loudness be-tween two sounds which decideswhether they are going to inter-fere. If one is but a small frac-tion of the other, it will cause notrouble.

Applying this principle to radiowe see that static will come inusing the very best set possible.If the broadcast is received inabout the same volume, then theformer will be very annoying. To

get a bigger ratio we must eitherdecrease the static or increase themusic. Since, as already shown,the static has already been re-duced to the limit, the evidentanswer is to make the programlouder. If this is done, then thedisturbance will apparently fadein the same proportion.

Godfrey Ludlow, Violinist. Mr.Ludlow, who has toured practicallyall over the world, gave five success-ful concerts in New York and wasacclaimed by the critics. He is nowon the staff of WJZ and WJY and isscheduled for special Sunday Con-certs from ten to ten -thirty. Mr.Ludlow had the signal honor of noless than six royal commands, receiv-ing many beautiful gilts. He is theproud possessor of the famous deRougemont Strad, dated 1703.

Real He -PowerThat is the big end and aim in

the idea of raising the output ofbroadcasting stations up to 2000watts and more. At the presenttime in the United States thereare thirty stations which have anoutput of more than 500 watts.Four of them are now puttingout 2000 watts, and one (KDKA)has at times used as much as 5000watts. If you are within a few

hundred miles of one of thesebig stations, you will realize thatwhen listening to it you are nottroubled by static, except onnights of severe weather dis-turbances. Of course, a thunderstorm may put even your Belltelephone out of order, and it ishardly to be expected that undersuch conditions your music willbe undisturbed. But it certainlyis true that these large amountsof power are a big help in over-coming outside noises.

Many people ask why local re-ception is not troubled by static.It is foe this very same reason.Your receiving set picks up somuch energy from the nearbysending station that in compari-son static fades to nearly nothing.It is going just the same as be-fore, but you do not notice it.

The Blanketed StationOf course, the big objection to

such increase is this: When youwish to pick up a good program1000 miles away, you find thatthe local sender has blanketed theair over a broad enough band sothat you can not get through him.Naturally, if he should increasehis power, it would blanket astill wider frequency band onyour dials. This objection is agood one and must be considered.But it is not the whole story.

If every station were to doubleits power, then the relativestrength of each would remainjust the same. A DX station,which you could just pick upthrough the local interference be-fore the change, would come inexactly the same after bothpowers had been increased. This,then, would be neither a help nora hinderance as regards selec-tivity between one station andanother. But notice the effect onstatic. If the latter had beendoubled at the same time theneverything would stand as be-fore. But static has not been in-creased. As a result its propor-tion is now only half what it usedto be, and so it is no longer a seri-ous bother.



New Radio College for WomenGreatest Interest is BeingAroused in These New Courses

1'HE new bride, who complained tothe grocer that his flour must be

tough because the bread she made waspoor, certainly had never taken a courselike that given by the new radio col-lege, which has just been opened forwomen.

So far radio has been directed mostlyto the attention of the male sex. It islargely the boys who build the newhook-ups and the men who write thechecks for the factory built sets. As theart has advanced, however, it has begunto appeal more to women. They arenow undoubtedly responsible for thechoice of a large portion of the radiosbought, and that explains why themanufacturers are now devoting somuch attention to giving them a goodappearance and making them harmonizewith the furniture of the home.

So it is not surprising that broad-casting programs are coming more andmore to include numbers of interest tothe feminine mind. This air collegeidea seems to be appealing very strong-ly to the women. Indeed, it ought to,because it is very well worked out andthe topics which are taken up are veryinteresting. It is even whispered thatthe husbands of some of these new "col-lege girls" are as much interested in thecourse as their wives, as they notice adistinct improvement in the cooking andthe household management.

New York State 'College of HomeEconomics at 'Cornell University, hasadopted a new method of giving exten-sion courses to the home -makers of thestate. Station WGY, Schenectady, hasbeen given a place on the faculty, andhenceforth, twice a week, the voice ofthe General Electric Company broad'casting station will be heard in thegreat class room which extends far 'be-yond the boundaries of the state.

Two Authorities at HeadOn Monday and Thursday afternoons

at 2 o'clock, the wife and mother incity and country home, may attend this"air college" and hear the latest in

styles, clothing, house furnishing, nu-trition, household management, andequipment. All these talks will be pre-pared under the supervision of the di-rectors of New York State College ofHome Economics,-Professor MarthaVan Rensselaer, and Professor Flora

Miss Martha Van Rensselaer

Rose, who are international authoritieson the subject of home economics -

Problems suggested by the talks maybe taken up by letter with the collegeby women who are residents of New YorkState, and all will be answered withoutcharge. Residents of other states mayreceive the same service 'from homeeconomics schools in their own states.The experience and knowledge of thecollege faculty as well as the benefitsof a research department supported byUncle Sam, will be offered those wholisten to the semi-weekly radio talks.

The following titles give an idea ofwhat may be expected in the radio ex-tension course:

Outline of CoursesClothing series 'How to Select Stock-

ings; How to Pick Out Gloves; TheSelection of Hats; 'Storing WinterClothing; Choosing Spring Fabrics;Clothing Budgets; Becoming Clothes forThin People; Suitable Styles for StoutPeople; How to Press Garments; Helpfor Home Sewers; Becoming Colors inClothing.

Homes Furnishing Series-Selectionand Hanging of Draperies; Picking OutRugs; Choosing and Hanging of Pic-tures; Color in the Home; The Artistryof the Table; The Use of Dyes in theHome; Decorative Use of Flowers.

Nutrition Series-Selecting Meals;Cost of Food; Vitamins in the Diet;Sunshine and Nutrition; Diet for Ex-pectant and Nursing Mothers; HowCornell Babies are Fed; Feeding thePre -School Child; Diets for the Over-weight; Menus for the Underweight;Suggestions for Overcoming Constipa-tion; Fixing the 'Child's Habits in Pre-school Years; Development of Personali-ty in Children; Fears of ChildhoodDiscipline of Children.

Household Management Series-TheFamily Resources; Division of Income;The Family's Savings.

Eotipment S e r i e s-Refrigerators;Washing Machines; Vacuum Cleaners;Springs and Mattresses.

A List of Good SpeakersIn addition to the directors, the

speakers will include Ruth Scott, Char-lotte Weiss, Frances Scudder, BeulahB'lackmore, Beatrice Hunter, Dr. NelliePerkins, Ruth Kellogg, Annette J. War-ner, Dora Wetherbee, Helen Monschand Nancy McNeal Roman.

The bill changing the School of HomeEconomics into the New York StateCollege of Home Economics was signedby Governor Alfred E. Smith, and be-came a law February 24. The gover-nor's signature made this the first col-lege of its kind in the world. The suc-cess of the bill was due in large partto the enthusiasm and support of thewomen of the state through the HomeBureau Federation and Federation of


Women's Clubs, as well as other organi-zations which have labored to get recog-nition of the work in which they are somuch interested.

There is probably no greater authori-ty on the subject of home economics thanProfessor Martha Van Rensselaer (Fig.

Miss Flora Rose

1) who, because of her achievements,was selected as one of the twelve great-est living American women by the Na-tional League of Women Voters. MissVan Rensselaer is director not only ofthe New York State College of HomeEconomics, but also of all home econo-mics extension work in New YorkState. She is state leader of the homedemonstration agents who work with thethirty-five organized home bureaus ofthe state with a membership of 30,000women.

Long before Cornell University had adepartment of home economics, MissVan Rensselaer organized a well devel-oped extension program for the farmwomen of the state as part of the ex-tension service of the college of agri-culture. This service was continued anddeveloped into the present program inhome economics, which includes bulle-tins, correspondence courses, specialists'service, and home bureau work. Thismakes it possible for any woman in thestate to receive information on anyhome -making subject by writing direct-ly to the college of Home Economics or

to the home bureau agent representingthe college in the county.

Has Over 500 PupilsIn 1907 the department of home eco-

nomics was organized and Miss VanRensselaer and Miss Flora Rose werenamed as heads and together developedits work, until in 1920, it was made aSchool of Home Economics with therank of a professional school in theState College of Agriculture. The schoolnow has six departments with over 500students taking courses and 450 of themspecializing in home economics.

During the period of the war, MissVan Rensselaer was in Washington asdirector of the home conservation divi-sion of the National Food Administra-tion. She has served on many state andnational educational committees, andwas president of the American HomeEconomics Association during the earlyyears of its existence. She is now editorof the home -making department of De-lineator, and is well known as a writerof magazine articles and as a publicspeaker. She has written many bulle-tins issued in the Cornell ReadingCourse for the home and, with MissRose and Miss Helen Canon, is the au-thor of the Manual of Homemaking.

5 -Year Health ProgramProfessor Flora Rose. (Fig. 2) the

other director of the College of HomeEconomics, was appointed director ofhome economics in New York State forthe United States Food Administrationduring the war. She has served onmany important home economics com-mittees in various organizations, and isnow a member of the nutrition commit-tee of the Milbank Memorial Fund,which is conducting a five-year healthdemonstration in Cattaraugus County.In 1923 she made a survey of the nutri-tion of the school children of Belgium atthe request of the Educational Founda-tion of the Committee for Relief in Bel-gium, of which Herbert Hoover is thepresident. Five thousand school chil-dren were studied in this survey anddetailed data of the nutrition and healthof each child was compiled.

DISTORTION A GOOD THINGContinued from Page 22

three high frequencies and in additionthere will be all the possible combina-tions of sum and difference frequencies.

If you will set these down yourself, ascan be easily done, you will find quite anarray.

To make it easy let's call the highestfrequency A, the middle one B, and thelowest one C. Then in our output weshall have these three vibrations, A, B,and C, and in addition A-B, A+B,A-C, A+C, B-C, B+C. The addi-tions of any two of these frequencieswill be around two million vibrationsper second and will be even fartherabove the notes that we can hear thanthe separate ones were. For that rea-son they have no effect on the opera-tion. But you will find two of these,A-B and B --C' both of which give theanswer 1,000. This is the same as thespeed of vibration of the note whichwas originally sung, and so we hearthat same tone in our loud speaker.

Mix and Unmix the MessageThus we see that it is as a result of

its distorting characteristic that a tubecan first modulate a carrier frequencywith a message frequency, i. e.,"scramble" the two together so thatone carries the other, and then at the

station "unscramble" them andgive us the original message.

While we have applied this to thecase of a simple message of constantfrequency, it holds equally well if themessage is varying in its vibrationspeed all the time, as is true in thecase of the complex telephone currentswhich we use for broadcasting of musicand speech.

Now this feature of distortion is notcharacteristic of vacuum tubes alone,but must be present in every form ofdetector which can be used in the radioart. If it doesn't distort, it will notdetect. It is also present to some ex-tent in many other things where it isnot wanted, such as telephones, micro-phone diaphragms, etc. This has beenrecognized for a long time and every at-tempt is made to reduce it. In radio,however, as just explained, there arecases where we wish to use a propertywhich was formerly considered undesir-able. We have here an illustration ofthe fact that however varied may be thebehavior of things in nature and how-ever undesirable some of these may ap-pear to be, there may come a time anda place where we want the very actionthat we formerly wished to avoid.


Radio The Doctor of the DeepSickness at Sea is Now CuredThrough Wireless Waves

YOU rush the sick child to the-ILdoc-tor's office, knowing that quickaction is needed. There you are toldthat the doctor is out. But imagineyour feelings if the doctor were out andwould "not be back for weeks.

That is about the situation that agood many sailors have been in sincethe days of Columbus. Of course, thebig ocean liners each carry a doctor andperhaps an assistant. But the smallerboats, the freighters and the sailingvessels, with their crews of eight or tenmen, naturally cannot afford to carrya physician. But now radio has steppedinto the breach.

Coffee Crew Falls SickThis is the way it works. A ship has

sailed from Brazil on its way to NewYork with a cargo of coffee, for ourbreakfast beverage. When still three orfour days out from land, one of the menis taken ill. This ship, like numerousothers, carries no doctor. Yet here is acase for a physician. It may be a ques-tion of life or death. Medical advice isurgently needed. What is to be done?

Fortunately, this freighter is equippedwith radio apparatus. The Radio Opera-tor is soon pounding his key, andshortly after, his call is picked up by an-other vessel miles away, in reply to theunwritten code of the sea. This is themessage received:S. S. West Adrian

To Captain S. S. Glenworm Castle,Man has intense swelling right side

face. Does not abate. Patient delirious.Have you a. doctor on board to wirelesstreatment ?

Captain.A few moments later the Radio Ope-

rator with his phones glued to his ears,picked up his pencil and jotted down thereply on his radiogram blank:

S. S. Glenworm CastleTo Captain West Adrian,

Keep patient in bed and treat facewith hot applications of water. If notsuccessful paint inside of jaw with whiteiodine. Advise results. Captain.

A few hours later the captain advisedthe distant doctor via radio that thepatient had been relieved and was rest-ing as well as might be expected. Thisexchange of radiograms probably re-

sulted in a life being saved.

THE LONG AND SHORT OF IT

There's quite a difference in sizebetween the little organ pipes heldby the girl and the large ones besideher. The pipes are part of theWurlitzer organ in the CrosleyWLW broadcasting studio in Cin-cinnati.

S. S. West AdrianTo Captain Glenworm Castle,

Patient resting easily after treat-ments and pain greatly relieved. Pleaseaccept my compliments and thanks.

Captain.It was not always possible to get

medical aid like this. The way it be-gan makes an interesting story. Overfour years ago Radio Medical Servicehad its modest beginning in an idea de-veloped by Captain Huntington, Chiefof the Medical and First Aid Course forseamen at the Seamen's Church Insti-tute, 25 South Street, New York City.He described his plan to Dr. Mansfield,in charge of the institute, who imme-diately saw in it a practical and humaneservice.

Right of Way Except S. 0. S.On November 3rd, 1920, a special com-

mercial wireless telegraph station li-cense with the call letters KDKF' wasissued to the institute. Soon KDKFbegan to desseminate medical service toships in its vicinity, from 9:00 A. M. to5:00 P. M., during the period the insti-tute's doctor was on duty. The idea,now given the acid test of actual ser-vice, proved highly practicable. KDKFsoon received the right-of-way over allcalls except the SOS of ships in distress.And soon it became manifest to all intouch with the development that theradio medical service must be runningtwenty-four hours per day. So on April20th, 1921, KDKF was licensed to oper-ate continuously.

The day and night service was madepossible when the Public Health Servicetook an active interest in the institute'swork and offered the services of its staffat the Marine Hospital located on Hud-son Street, so as to furnish medical ad-vice by night as well as by day. Adirect telephone connection, was madebetween the institute and the hospital,and in this manner speedy medical in-formation was now on tap for the lonelysteamer within ready reach of NewYork.

28 RADIO PROGRESS MAY 1, 1925,

The Range Too SmallOne more obstacle still confronted the

service, and that was the question ofradio range. The radio transmitter atthe institute was not powerful enoughto reach ships at any considerable dis-tance from New York, so that in manycases it became necessary to relay themessages. The medical service hadgrown all the while and increased itsscope of usefulness, but the Seamen'sChurch Institute did not possess thefunds nor the equipment to carry on thework which bad reached such vast pro-portions.

At this stage in the development ofthe radio medical service, the matterwas brought to the attention of theRadio Corporation of America. The or-ganization, fully aware of the far-reach-ing importance of the radio medicalservice and the necessity for extendingthis humane and worthy cause, imme-diately donated the use of its stationsfree of charge, and instructed its ope-rators to be constantly on the watchfor calls for medical aid. Thus the radiomedical service passed out of the narrowconfines of the little transmitter of theSeamen's Church Institute, and becameavailable through a large network ofcoastal radio telegraph stations. Sincethat time the R. C. A., in co-operationwith the U. S. Public Health Hospitalat New York and other ports, has beenhandling this radio medical service.

Norway the Next NationThe service, in the course of its rapid

expansion, has taken on an internationalaspect. On June 7th, 1923, it was

learned that the Norsk Marconi Kom-pani of Christiania, Norway, would givefree medical service to ships of any na-tionality through its stations in Norwayand 'Sweden. So, the germ of an idea byCaptain Huntington, developed and per-petuated by the personnel and equip-ment of the R. C. A., has spread to allparts of the globe and now any shipseeking medical aid is promptly served,merely in the interest of humanity.

The Chatham Coastal Station, themost powerful of its kind in the world,with the call letters 'W1M, listens forcalls for medical service in the Bostonvicinity. WIM is so powerful that itoften handles medical service messagesfrom all parts of the Atlantic, fromclose to Europe down to the Gulf ofMexico.

United Fruit Co. Also ServesRadio medical service for the North

Atlantic and North Pacific is handled bythe+ high powered stations, but in theCarribean Sea and adjacent waters, theUnited Fruit Company has inaugurateda free service through its splendid hos-pitals established in tropical America.

As you gaze at the sky it seems in-credible that through the apparentlyempty air this merciful work is quietlyfunctioning all the while. Indeed, sideby side with the radio waves that bringprograms into your home, there are thewaves bearing the code dot -dash mes-sages of ship -to -shore traffic, some ofwhich is devoted to the radio medicalservice. Countless radiograms bear wit-ness to cures by stating at the close ofthe ease, "Patient 0. K., normal yester-

day, and to -day no symptons of anykind; many thanks."

More than one operation has been per-formed by the ship's crew, workingunder the direction of a surgeon manymiles away. In such instances the sur-gical instruments have been of an im-provised nature-kitchen knives, ordi-nary scissors, pieces of wood, and so on-but always quite in keeping with thelay hands that wielded them.. Still,such long-range surgery has accom-plished wonders. Surgical cases, as acuteappendicitis, must be caught in the nickof time lest they prove fatal. In theirfirst start, lay methods will work great-er wonders than the efforts of the fore-most surgeons when the case has ad-vanced to the fatal stage. Hence radiooperations have been the means of sav-ing many a life which would otherwisehave had to be forfeited for lack ofearly surgical care. Radio operationshave often provided temporary reliefuntil the ship could make port.

Crew Has Been PoisonedOnce the U. S. Liner "America" picked

up a stray message from a lone freight-er stating that nineteen members of itscrew were suffering from a painfulmalady. Only the vaguest details wereforthcoming as would be expected fromlaymen. The vessels at the time weresome three hundred miles apart-ob-viously a case of long range diagnosis.Putting their heads together and work-ing on the meagre details, Drs. C. F.Leidy and Hislop diagnosed the ailmentas ptomaine poisoning. For two days


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km. TEIAGRAPH PC"rELeeRisrl10 'or 1420.0 SrgioN .-=TELL'm-To 51bp PoPpirao POP-CORN IN PER grvOIO ASVEE CAN HEAR IT!!

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NOTE: In this section the Technical Editor will answerquestions of general interest on any radio matter. Any ofour readers may ask not more than two questions, and ifthe subjects are of importance to most radio fans they willbe answered free of charge in the magazine. If they are

Question. When is it desirable tooperate with two different kinds of tubesin the same set?

Ansewr. Of course, the most usualcase is where a UV -200 is used for a de-tector and UV -201A tubes for ampli-fiers. They both require the same pres-sure -5 volts. Probably what you havein mind, however, is sets which employUV -201 A tubes for audio amplifiers andUV -199 for radio frequency amplifiers.The advantage of such a scheme is thateach of these two styles is the best forits particular class. The 199 tubes donot have as great a volume for audiowaves as the 201A and so do not putout as great a volume through the loudspeaker. They have plenty for radiowaves, however.

On the other hand, the 201A tubeshave a great deal more internal capacitybetween grid and plate and so waste agood deal of the high frequency energy.Such a trouble is not found with thelow frequency audio vibrations. Ofcourse, such a scheme requires higher re-sistance rheostats in series with the the199 tubes than with the others; 60 ohmsis not too much.

Question. Why do the manufacturersof "B" battery eliminators tell you notto measure the voltage with an ordinarytester ?

of special interest to the questioner alone, or if a personalanswer is desired, a charge of fifty cents will be made foreach answer. This will entitle the questioner to a personalanswer by letter. However, if the question requires consid-erable experimental work, higher rates will be charged.

Answer. The ordinary eliminators onthe market have an output of 15 to 25milliamperes. This is enough current tooperate up to five or six tubes. How-ever, the ordinary "B" battery testertakes considerably more than this to

read even as high as fifty, and so when itis used to test the voltage it is like try-ing to measure the water pressure at afaucet with the water turned on andrunning out in a stream. Of course, insuch a ease the water pressure drops solow that the gauge reading is not worthmuch and in the same way the voltagewill fall off owing to the heavy drainthrough the meter so that the readingdoes not mean anything. Only a specialhigh resistance volt meter can be usedfor such tests.

Question. What is the advantage ofradio coils shaped like a doughnut?

Answer. The real name for such ashape is the toroid. For the benefit ofsome of our readers who mean by"doughnut" the kind of goody which hasthe ends twisted together, we might saythat the toroid is the shape of a lifepreserver, which has a round sectionwhen cut across. If you take such ashape of winding form and wind thewire around it threading it in and outthrough the center hole, then you get acoil which is unusually efficient in thatit is not affected by outside magnetism.

You see that any magnetic lines whichstruck it on any side would go aroundcounter clockwise say at the top andclockwise at the bottom, and the twoeffects would neutralize each other. Inthe same way the magnetic effect thatsuch a coil has is confined almost en-tirely within the winding. Since thelatter loops back on itself, there is nochance for stray magnetism to get outand interfere with other coils in thesame set. This, in a large measure,prevents the magnetic feedback in a setlike a neutrodyne from causing the RFamplifier tubes to oscillate.

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Fone Fun For FansIt Specializes That Way

A lemon can afford to be sour. It hasto be sour to be successful as a lemon.As we are not trying to be lemons:let us smile.

Able to WalkMan-"Is New York the next stop?"Porter-"Yas, sah; brush you off,

sah?"Man-"No, I'll get off myself."

-Western Christian Advocate.

The Teeth of the StormDing-What did your wife say when

you got home last night"Dong-She never said a word. And I

was going to have those two front teethpulled, anyway.-Crosley Radio.

MellerdranimerHero-Cur! Where are those papehs?Villain-They are at the blacksmith's.Hero-Ha! You are having them

forged?Villain-No, I am having them filed.

-Awgwan.

Careful George"I say, George," said the young busi-

ness man to his friend, "where do youbuy your typewriter ribbons ?"

"I don't," replied the other, "I usuallybuy her flowers."-Tit-Bits.

New Name for itShe (anxious to impress)-"I've just

put my furs into cold storage."The Fool-"Cold storage! Ha!-jolly

good-never heard it called that before;my cuff links and watch are there too."

-London Opinion

All Quiet in the Building TradeCountry Cousin (after prolonged in-

spection of building operations)-"Idon't see the sense of putting statues onthe top of your buildings."

Friend-"Statues? Those aren't sta-tues. They're bricklayers."-Punch

AffectionatelyHe thought he'd surely made a hit,

When for his photograph she prayed."Out, when this calls," she wrote on it,

And gave it to the maid.-Amherst Journal.

In the Kitchen"What was that-er-scuffling in the

kitchen a short while ago, Jane ?""Why, sir, that was the cop tryin' to

kiss me.""Aha! And you forcibly objected?""I didn't, sir, but the letter carrier

did."-Judge.

EDITOR'S LOUD SPEAKERContinued from Page 24

Sky the LimitOf course, this idea could be

carried still further until thepower of the larger broadcastersreached five, ten, or perhaps evenfifty kilowatts (50,000 watts). Itis hard to say just where the limit(if any) would be. That is whythe Department of Commercekeeps increasing the upper limitwhich is permitted for the powerof sending stations. It does thisin small steps of not more than500 watts for each change. Ifenough opposition to these in-creases was heard from broadcastlisteners, then power would notbe permitted. So far, however,the number of complaints against

the increase already_ granted havebeen very small indeed.

It certainly looks as if thissummer would see less botherfrom static than ever before, andthat increased power was the an-swer to this perplexing problem.

DOCTOR OF THE DEEPContinued from Page 28

the men of the freighter were treatedby radio instruction. Then this messagecame back to the "America": "Your di-rections followed. All but six now onduty. They are recovering fast. Thanksand God bless you. Bon voyage."

At another time another freightercalled to the "America" stating that amember of its crew was in dreadfulagony. The doctor then aboard the"Arnerioa" studied the case by means of

the meagre data supplied, and then pre-scribed by radio. The following day amessage was received from an Italiansteamer some 300 miles away in an en-tirely different direction stating, "Manythanks to S. S. America. We had sickmember of crew suffering from similarailment. Prescribed same as directedfor other steamer. Our patient recov-ering. God bless you." So, what wasintended for a specific case also came inhandy for another. In this particularinstance the radio medical service of 11.e"America" had been truly broadcast.

And sea babies! The stork does notalways select his visits in keeping withcarefully laid plans. Sometimes he in-sists on paying a visit aboard a ship-even a ship without medical aid at hand.Here again the radio medical servicesupplies the necessary expert direction,while lay hands do the work.

This Prevented a MistakeSerious mistakes have been prevented

in many instances as evidenced by suchradiograms as these:Marine Hospital,New York.

We have seaman with crushed hand ingreat pain. Only available relief spiritsof chloroform. Please advise how to useand means of dressing hand.

Master, S. S. Comber.The unfortunate seaman had much

cause for gratitude, as the responsefrom land read:Master S. S. Comber,

Do not use chloroform. Clean handthoroughly and apply iodine if you haveit. If no iodine use water and applyheat in form of hot water bag or towel.

Medical Service, N. Y. C.Often the hospital's advice will be

"Take patient to nearest port as soonas possible. Arrange by radio to haveambulance meet your ship on arrival."Indeed, by the time the patient arrivesat the hospital, the doctor is already fa-miliar with his case, so that no time islost in bringing him back to health.

Medical Service Beats BroadcastingIn the radio medical service we have

but another instance of the versatilityof radio and its vast capacity for ser-vice. The public at large is too apt toconsider radio only in terms of radiobroadcasting which, after all, is mostlyentertainment. But in the radio world,the broadcasting phase is of minor im-portance only, when considered side byside with commercial radio traffic.

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Extracts from a Few of the Many

LOVE LETTERSFROM THE READERS OF "RADIO PROGRESS"

And Not One of Them Solicited

"The style of your magazine and its mottoare so good." F. J. PORTER,

U. S. Patent Office, Washington.

"Your Mr. Taylor is the only writer whosework has been so clearly worded that I couldget the idea with little effort. 'More power tohim.' " B. W. PERCIVAL, Lynn, Mass.

"We like RADIO PROGRESS, but don't see enoughof it !" II. S. FRAINE,

of Doubleday, Page & Co., N. Y.

"Your magazine gives so much on the funda-mentals of radio that I have decided to sub-scribe for it. Most people depend on this mag-azine to keep them instructed -on the subjectabout which the publication deals. Very fewbuy books. I appreciate it very much and hopeit will grow large." DR. J. S. CANTRELL,

Proprietor Snowwhite Eggfarm, Carthage, Mo.

"I like RADIO PROGRESS because its articles areclear and concise, especially those of H. V. S.Taylor." A. A. CONSTEIN,

Ph. G., D. D. S., Upper Sandusky, Ohio.

"RADIO PROGRESS is the most interesting radiomagazine I have yet seen, and strikes a happymedium between being too technical and ignor-ing technical explanation altogether. May 'youlive long and prosper.'"

(Dr.) M. S. DELAND,State Hospital, Topeka, Kan.

"Your magazine has a very pleasing presen-tation of its subjects without too much techni-cality, and understandable."

A. J. WERTZEL,Vice. Pres. United States National Bank, Su-

perior, Wis.

"Enclosed find 50c. for copies Nos. 9, 10 and11 of RADIO PROGRESS to COMPLETE MY FILE,as I missed them while on my vacation."

FRANK HANUS, Cleveland, Ohio.

"I like your magazine very much and hopeyou will keep up the good work in publishingsuch clean cut articles." E. T. LEWIS,

Baltimore, Md.

"Interest in your progressive little magazineas well as the desire to obtain the special hook-up number of Jan. 15th has prompted me toenclose," etc. Con.uss GALLOGLY,

Alden, Minn.

"I like your magazine very much."JOHN GILLMAN, Long Island City, N. Y.

"While your magazine may not have the bulkof some of your contemporaries the subjectmatter is excellent, being clearly written andaccurate." E. J. WAGNER, Chicago.

You. Radio ManufacturersWho want to advertise where you can make the largest sales for the smallest

expense will never do it until you advertise in RADIO PROGRESS

There are 20,000 other readers like those above who are awaitingyour announcements.

)11111) 11 1)11111

TOBE C.(DEUTSCH MAN N

r3ine Radip 'pparatus

STATIC ELIMINATIONWITH the approach of summer, every radio

fan lOoks with a certain amount of dreadto the Enigma of Radio-Static. For more thana quarter of a century, scientists in many parts ofthe world have applied their knowledge and skillto the problem of eliminating Static. Most oftheir attempts have resulted in failure.

Science recognizes but one device capable ofcurbing the annoying electrical disturbances, andthat is the loop antenna. Electrical storms, likeother weather disturbances, find their origin invarious points of the compass. It is obvious,then, that by the use of a directional loop turnedto a direction away from the disturbance, thedisagreeable static noises may be tuned out.

The superior construction of the DTW IMPORTED COLLAPSIBLE LOOPenables it to perform this function to much better advantage than other loopantenna devices. Forty-two inches high by forty inches wide, its inductanceconsists of fourteen turns of genuine Litzendraht cable, made up of sixtyindividual strands, insulated, twisted and covered with double green silk.

The woodwork is mahogany and all metal parts are highly nickeled. Agraduated metal table at the base accurately gives the station direction. Theturns are sectionized and by unique design all "dead end" effect is absolutelyeliminated. The center tap permits its use without modification for all typesof Super Heterodynes. The loop is collapsible and by means of the adjust-able slide it may be actually used as the tuning unit of the set. No otherloop incorporates such perfection of design, and no other loop can give suchmarvelous results.

Price, $25.00CUT OUT

1111 11111

I am interested in the DTW loop advertised in RADIOPROGRESS.

Please send me literature descriptive of the loop.

(Name).

(Street).

(City). (State)

TOBE C. DEUTSCHMANNSole American Distributor

46 CORNHILL, BOSTON. MASS.

I.

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II

II

1

1

11I

I111I

11I

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poq

How To Clean A Crystal

There is only one good way to clean a crystal from your receiving set. If you follow di-

rections carefully, you will not only get reception as good as formerly, but ten to one it will be

better than you ever brought in the music before.

Here is the way to do it. Take a 25c piece or 25c in stamps and send it to us with the re-

quest that we ship you an Audion Crystal. When you get it through the mail throw your old

one on the dump. The result will be that you do not have to hunt for a sensitive spot on thecrystal any longer, but by dropping the cat whisker anywhere you will get the music in as loud

as you did on the best spot of your old- crystal.

Perhaps you do not know that by combining a crystalwith a single tube and using one of our RADICLEARaudio frequency transformers you can get loud speakervolume from the crystal detector. Of course, you willnot be able to get more than fifteen or twenty miles rangewith the normal set but a local station is loud enough fordancing.

The particular advantage of the crystal is its cleartone. There is no distortion at all. If you combine thiswith an ordinary transformer which distorts, it is likegetting a wonderful singer and then listening with cottonstuffed in your ears.

One reason for the clearness of the RADICLEARtransformer outfit is in the grade of Silicon steel used inthe core. This is expensive, but we find that it pays divi-dends in the smoothness of the tone produced. The priceof the transformer is $3.95. If you wish the rest of thekit consisting of socket, rheostat, "B" battery terminal.

jack and wiring, then $6.00 covers the entire equipment. Use the coupon in the corner.

The Taylor Electric Company,1206 Broad Street,Providence, R. I.

Please send me the following by par-cel post. (Mark which one you want.)

Radiclear Audio Transformer @ $3.95Amplifier set complete @ $6.00

(Socket to fit tube)Audion Crystal @ 25c.Gold Plated Cat Whisker @ 15c.

I enclose $.... to pay for these.(These above prices include the postage.) Send them to me C. 0. D. I

will pay the above price plus postage.(Indicate which way you wish to pay.)

Name

Addres,

TAYLORELECTRIC CO.

1206 Broad Street

Providence, R. L

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