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Application NoteAN-43copyright

January, 2018

KH6HTV - TVRBoulder, Colorado TV Repeater

Jim Andrews, KH6HTV

REPEATER CALL SIGN: KH6HTV , also uses KH6HTV-TVR

TRUSTEES: Trustee is Jim Andrews, KH6HTV, www.kh6htv@arrl.net Assistant Trustee is Don Nelson, N0YE, don80303@gmail.com

MODES: Digital & Analog TV for both receive and transmit. Particular mode isselected by control operator. Normal stand-by mode is: 23cm DTV receive and 70cmDTV transmit. Digital is European standard, DVB-T with 6 MHz bandwidth. hi-def video, stereo audio 70cm Analog is NTSC, VUSB-TV with 4.5 MHz, mono sound sub-carrier, 480i video23cm, Analog is NTSC, FM-TV with 4 MHz deviation, positive polarity sync and 5.8MHz, mono sound sub-carrier, 480i video

CCARC FREQUENCY COORDINATION: Coordination is for DVB-T input andoutput. Input = 1243 MHz, (1240-1246MHz) Output = 423 MHz, (420-426MHz)

FREQUENCIES: 70cm in band and also cross-band 23cm / 70cm repeater.70cm Output = cable channel 57 (420-426 MHz), ARRL designated repeater outputDigital Output = 423 MHz center frequency, 6 MHz bandwidth, DVB-T modulationAnalog Output = 421.25MHz video carrier frequency, 425.75MHz, FM sound sub-carrierfrequency, 420-426 MHz, channel 57, NTSC, VUSB-TV modulation

23cm Input = ARRL, ATV-1 channel (1240-1246MHz)23cm Digital Input = 1243 MHz, center frequency,6 MHz bandwidth, DVB-T modulation

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23cm Analog Input = 1247 MHz, center frequency, NTSC, FM-TV, 4 MHz deviation,5.8 MHz, FM sound sub-carrier

70cm Input = cable channel 60 (438-444MHz), ARRL designated repeater input, Notcoordinated with CCARC70cm Digital Input = 441 MHz, center frequency, 6 MHz bandwidth, DVB-T modulation70cm Analog Input = 439.25MHz video carrier frequency, 443.75MHz, FM sound sub-carrier frequency, NTSC, VUSB-TV modulation

PL TONES REQUIRED: The input signal must be a valid TV signal, thus preventingthe repeater from being keyed up by CW, SSB or FM voice signals. For analog NTSCTV signals, the repeater detects the presence of horizontal sync pulses at 15kHz for key-up. For digital TV signals, the receiver must decode valid DVB-T signals to key-up.

OUTPUT POWER:70cm Digital = 5 Watts (rms, avg) & 50 Watts (ERP)70cm Analog = 14 Watts (PEP) & 140 Watts (ERP)

ANTENNAS:70cm Transmit antenna is Andrew model DB-411. 11dBi gain, cardiod pattern, orientedto 30o from true north. 2m/70cm/23cm receive antenna is Diamond model X-6000.mfgr's spec. is 6.5/9/10dB, omni directional pattern. Antenna heights are approximately120 ft. and 100ft. above ground level. Polarization is vertical for both antennas.

Fig. 1 Yellow thumbnail shows the location of NCAR and the TV repeater.

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Fig. 2 NCAR with Flatiron mountains to the west (left) and view over the prairie to the

east (right).

Fig. 3 NCAR with the TV repeater antenna on the roof at 120 ft. above ground.

REPEATER LOCATION: National Center for Atmospheric Research (NCAR). 1850Table Mesa, Dr., Boulder, CO, 80305 39o 58' 39.83" N x 105o 16' 27.84" W, 6,100 ft.elevation above sea level.

HEIGHT ABOVE AVERAGE TERRAIN: HAAT is -193 ft. Note: negative number.This is due to the shielding effect of the high Flatiron mountains to the west.

SERVICE AREA: Eastern half of Boulder, County

DVB-T TRANSMITTER DIGITAL PARAMETERS: The DVB-T transmitter iscapable of transmitting very high definition images up to 1080P with 64-QAMmodulation. However, to maximize it's range with low power over difficult terrain withlots of multi-path, we have opted to instead transmit lower resolution, 720P video with,QPSK modulation and with very aggressive encoding. The digital parameters are: TransConfiguration : Freq = 423 MHz (ch 57), BW = 6 MHz, modulation = QPSK, FFT = 8 K,Code Rate = 1/2, Guard Interval = 1/16, Modulation Data Rate = 4.39 Mbps MediaConfiguration: Video Encoding = H.264, Data Rate Control = CBR, Max. Bit Rate =3500 kbps (i.e. 80% of modulation data rate), Video Encoding Resolution = 1280 x 720,

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Video Frame Rate = 29.97fps, Video Aspect Ratio = 16:9, Audio Encoding = MPEG2,Audio Encoding Bit Rate = 96 kbps TS Info: Service Name = KH6HTV, PMT PID =0X640, Video PID = 0x641, Audio PID = 0x642

REQUIRED DVB-T INPUT PARAMETERS: Your DVB-T input signal to therepeater does not need to adhere to most of the above settings. However, it must be on thecorrect center frequency with a 6 MHz bandwidth and have the same PIDs. Otherwise,the DVB-T receiver is smart and will adapt and receive properly any DVB-T signal withmodulations of QPSK, 16QAM or 64QAM, and various resolutions, FFT, Code Rate,Guard Interval, etc.

SPECIAL FEATURES: The repeater also includes a BEACON Mode for aiding ininitial alignment and testing of receiving equipment and antennas. In the beacon mode avideo slide show is transmitted continuously with information about and photos of therepeater. This slide show is also transmitted as the ID at the end of a transmission tomeet FCC requirements. The repeater call sign is super-imposed on each slide. Therepeater can receive either analog or digital TV input signals on either the 70cm band orthe 23cm band. It can also transmit either analog or digital TV signals on the 70cm bandon channel 57. The particular operating mode is determined by the control operator.This is done remotely using a separate rf link with DTMF (touch-tone) control codes. Asecret password is required to access the control functions. To enable a particular set ofoperating conditions, you need to contact an authorized control operator. The normal,stand-by, operating state is with the repeater receiving 23cm DVB-T and transmitting70cm DVB-T signals. This is the CCARC coordinated condition.

OPEN REPEATER:The KH6HTV-TVR repeater is an "Open" repeater. It may be usedby all licensed amateur radio operators. However, the control access codes for the IDbeacon and all other special features are only given to amateurs that own their own TVtransmitters and have been approved by the trustee or asst. trustee. To request the IDbeacon be turned on, or further details on other special features -- contact either thetrustee or asst. trustee.

BOULDER TV NET: A weekly TV activity net is held in Boulder County everyThursday afternoon, starting at 3:00pm (local time). The purpose of the net is toencourage the use of amateur TV and to experiment with it's capabilities. The net is"Open" and all hams are encouraged to participate even if they do not have TV capability.The net typically uses the KH6HTV- TVR repeater and also simplex DTV. Voiceintercom is accomplished using the BARC, 2 meter, FM repeater (146.70MHz) which isalso co-located at NCAR and has similar coverage area. Currently , a lot of the TV net'sactivity is experimentation with high-definition (1080P), Digital TV using DVB-Tmodulation. For additional information about the TV net, contact the assistant trustee,Don, N0YE.

REPEATER TECHNICAL DETAILS: For detailed description of the designand construction of the TV repeater, the reader is referred to Application Note, AN-31,[1]. It is available in .pdf format from my web site: www.kh6htv.com

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REPEATER COVERAGE MAPS: The repeater provides coverage over mostof the eastern half of Boulder County and also out to portions of Larimer, Weld, Adams,Broomfield, Denver and Jefferson counties. Because of it's NCAR location nestled upagainst the Flatiron mountains, it does not provide coverage back into the mountainousareas of Boulder County. These coverage areas have been confirmed in many locationsby actual mobile field surveys. These maps have been computed using the on-lineprogram, Radio Mobile-Online, by Rodger Coude, VE2DBE.(http://www.ve2dbe.com/rmonline.html ) For more details about this program and TVpropagation in general, see app. note, AN-33a [2]. More detailed coverage maps areavailable from the trustee. Also, upon request, I can compute more detailed point-to-point rf path predictions to/from the repeater and your particular QTH.

Figs. 4-6 show predicted, overall coverage areas of the repeater. The assumed remotestation is a mobile station with a 3 watt DVB-T transmitter and a 1/4 λ, 2.2dBi, verticalantenna on the roof of the car. The yellow shaded areas are predicted weak signals of-90 to -80dBm. The green shaded areas are for strong signals > -80dBm. -90dBm(7μV) has been the weakest DVB-T signal we have been able to receive in actual practiceout in the field under typical multi-path conditions. Obviously, these coverage areas canbe increased by using higher gain and taller antennas, plus higher power transmitters.

Fig. 4 Coverage area for 70cm DVB-T transmissions from the NCAR transmitter to amobile unit with 1/4 λ antenna. Green > -80dBm Yellow = -90 to -80dBm. The redteardrop is NCAR.

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Fig. 5 Coverage area for 70cm DVB-T transmissions from a mobile unit with 1/4 λantenna to the NCAR repeater receiver. Green > -80dBm Yellow = -90 to -80dBm.

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Fig. 6 Coverage area for 23cm DVB-T transmissions from a mobile unit with 1/4 λantenna to the NCAR repeater receiver. Green > -80dBm Yellow = -90 to -80dBm.

REPEATER HISTORY: Boulder, Colorado has had anamateur Television repeater since the late 70s. Boulderhams, including myself, became interested in amateur TVstarting in 1974 when an in-expensive, small, partially solid-state, B&W TV camera became available from a bankruptcompany in Austria that had come out with an earlyconsumer grade video tape recorder. Most of the active TVhams then were also members of the Rocky Mtn. VHFSociety. The RMVHFS had a 2 meter FM repeater(146.76MHz) then on Lee Hill, north-west of Boulder.Under the sponsorship of RMVHFS, I, Joe Woods AD0I,John Shafer, W0KWR, and Bob O'Connell, WA0BAF,designed and built our first TV repeater and installed it at therepeater site on Lee Hill. It was a 70cm repeater with the

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input on 439.25MHz and the output on 421.25MHz. It used a single DB Products, DB-411, antenna with a circulator (25dB isolation) and separate 6 MHz, interdigital, band-pass filters on the receiver and transmitter. I designed and built the 10 watt transmitterand controller. Joe built the receiver, John built the band-pass filters. Bob did the wiringof the controller. This repeater was operational from about 1978 till 1981. It operatedunder the RMVHFS club call sign, W0IA. During this era all ham TV was in black &white (B&W), as no one could afford a color TV camera. In 1981, a new, powerful(10kW), FM broadcast transmitter was installed at the Lee Hill site. The resultant RFIwas so strong that we were unable to keep it out of our controller, etc. Thus, we removedour TV repeater from Lee Hill.

In 1980, I started my business, Picosecond Pulse Labs, and began working on it full timein 1981. For the next ten years, I was too occupied with PSPL to devote any time to hamradio or TV. The TV repeater sat in storage in my basement for the next ten years. TVactivity in Boulder died during this interval.

In the fall of 1989, Captains Bill McCaa and Chuck Pringle, of the Boulder CountySheriff's Department approached BCARES (Boulder County Amateur Radio EmergencyServices) and asked that BCARES provide TV services to the Boulder Sheriff'sdepartment for major emergencies. They promised to provide financial and othersupport for the project. At this time, I was the chairman of BCARES. Also at this time,several camera companies, like Canon, etc. had come on the consumer market with thenew idea of camcorders. These combined in one relatively inexpensive, small, hand-heldpackage, both a color TV camera with a zoom lens and also an 8mm video cassetterecorder. Thus, with the new color camcorders and the support of the Boulder Sheriff,BCARES accepted the TV challenge. We pulled out of storage our old 1970s vintageTV repeater. The Sheriff arranged for us to install it in the City of Boulder's radio site inChautauqua Park. The Sheriff also purchased antennas, and hard line, coaxial cable andprovided their radio technician to install the antennas using a city cherry-picker truck.We no longer had a circulator, so when the repeater was installed at Chautauqua Park, wenow used a pair of DB-411 antennas, one for receive and the other for transmit. We hadthe repeater back on the air by the summer of 1990.

At this time, Bill McCaa, also encouraged us to get the TV repeater frequencycoordinated with the CCARC ( www.ccarc.net ) to nail down the 421.25 MHz frequencyfor our exclusive use. The CCARC was unwilling to give us frequency coordination foran in-band 70cm repeater. They gave us the 421.25 MHz output frequency, but insistedthat we must be a cross-band repeater with our input on the 23cm band. They assignedus 1277.25 MHz as our input frequency. This was a very unfortunate choice as the thirdharmonic of the 70cm transmitter's sound sub-carrier at 425.75 MHz was also exactly1277.25 MHz ! ! ! I was thus faced with the difficult task of adding a 23cm receiver tothe repeater and also suppressing dramatically the third harmonic from the transmitter. Iaccomplished it, but not without a lot of effort. At this time, we also made the decisionto still retain the 70cm input capability at 439.25 MHz to support 70cm ATV transmitters.Granted this was against the CCARC ruling, but we felt it was needed to adequatelysupport the Sheriff's dept. Thus our 70cm input was un-coordinated with the state

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frequency coordinator. For remote control of the TV repeater, we used a simplex 2 meterchannel with DTMF (touch-tones).

In 1991, we also saw the need to have a portable TV repeater to be able to adequatelycover forest fires in the mountains of Boulder County. The Chautauqua Park TV repeatergave good coverage of the city of Boulder and the eastern plains portion of BoulderCounty. It didn't give any coverage of the western mountains in the county, except for thefirst ridge of foothills. I thus, started a project to design and build a portable, 70 cmin/out, 10 watt TV repeater. I enlisted Rip Van Winkle, NV0M, to assist me with thepackaging of the repeater. We managed to cram all of the necessary electronics into asmall (12"w x 8"h x 12" d) enclosure. This portable ATV repeater has performedflawlessly and is still in service to this day.

The 1970s vintage repeater and transmitters used were my own design using a Motorola,70cm brick amplifier. In the 1990s, all of the BCARES TV transmitters, including therepeater transmitter, were made by PC Electronics ( www.hamtv.com ). We had both 1watt and 10 watt transmitters. By the late 90s, we had added the capability to receive23cm FM-TV in addition to VUSB-TV. Over the succeeding years, I continued to makeimprovements in the various components of the repeater, with several major rebuilds.

During most of this time, the repeater operated under my own personal call sign whichthen was WA0NHD. In Dec. 2006, I changed my call sign to KH6HTV. This was donebecause now in retirement I was living for half the year in Hawaii and half in Colorado.BCARES felt that a KH6 call was not appropriate for the TV repeater. We thus appliedfor the vanity call sign, W0BCR, for BCARES, with me as the trustee. From that timeon, the TV repeater has operated under the call, W0BCR.

In 2012, we encountered a major problem with RFI on the repeater's 23cm input. It wasfrom a new FAA radar at the Denver airport operating on 1267MHz. I applied to theCCARC for permission to move our input frequency from 1277.25MHz to the bottomend of the 23cm band at 1240-1246MHz. The request was approved. With Don's,N0YE, help we were able to come up with a suitable band-pass / notch filter for the 23cmreceiver which rejected the extremely powerful radar pulses which were clobbering ourreceiver.

In 2014, I discovered DVB-T, digital TV and Hi-Des ( www.hides.com.tw ) as a supplier.This made a major transformation in amateur TV in Boulder, Colorado. BCARESadopted it for use in support of public safety. The Univ. of Colorado Police dept. fundedthe purchase of four complete DVB-T, portable, transmitters with all necessary otherequipment. Today (2018), almost all of the active ATV hams in Boulder are now onhigh-definition (1080P), digital, DVB-T, television. In the summer of 2016, I spent thewhole summer designing and rebuilding the TV repeater to make it a dual mode, analog& digital, TV repeater. It went back into service in the fall of 2016.

In the next summer of 2017, BCARES was given notice by the City of Boulder that theTV repeater had to be removed from the Chautauqua Park site. This was because the city

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wanted to expand their own radio system and needed the rack space in the radio shackand also the space on the tower for more of their own antennas. Since then the repeaterhas been in a couple of temporary locations. It was first at my QTH and then morerecently on Davidson Mesa at Roger & Naomi's QTH ( K0IHX & KD0PDZ ). Neithersite gave as good coverage as the Chautauqua site. A search was on for a better site. Aproposal was made to the Boulder Amateur Radio Club ( BARC ) to use their site and70cm antenna at the National Center of Atmospheric Research on a high mesa, south-west of the city of Boulder. BARC agreed subject to approval from the CCARC for themove. Approval was obtained from the CCARC in Jan. 2018. The TV repeater is nowbeing moved from Davidson Mesa to NCAR. At this same time, BCARES informed usthat they no longer wanted to be associated with the TV repeater. Thus, henceforth, therepeater will operate under my own personal call sign, KH6HTV, with me as the trustee.It thus no longer has any ARES affiliation.

REFERENCES:

1. "Digital & Analog TV Repeater", Jim Andrews, KH6HTV Video ApplicationNote, AN-31, Sept. 2016, 24 pages

2. "TV Propagation", Jim Andrews, KH6HTV Video Application Note, AN-33a,Oct. 2016, 12 pages