Triangle Amateur TV Association ...because a picture's worth a thousand words per minute.

What is Amateur TV?

You've heard of Amateur Radio, but have you heard about Amateur Television?  A small but dedicated group of FCC-licensed ham radio operators communicate with each other by means of their own personal color TV transmitters and receivers.  They call it "ATV."

The Triangle ATV Association...

is a non-profit corporation formed on January 14, 1993 by a group of about 22 hams from Raleigh, Durham, and Chapel Hill, NC.  The initial goal of the Association was to form an independent local organization that would promote Amateur Television in the Triangle by building and operating a state-of-the-art, wide-area coverage, ATV repeater.

The Triangle ATV Repeater:

In March of 1996, thanks to support from the Durham FM Association and the Raleigh Amateur Radio Society, The Triangle ATV Association's repeater was placed into service using the KJ4SO callsign of William "Woody" Winstead, now a "silent key."  In January of 2008, the current club callsign of NC4TV was issued.  The repeater is located atop TV Hill in northwestern Durham County NC, with a 360° view of the horizon that provides good coverage in the Raleigh-Durham-Cary-Chapel Hill area  (see map).

• Repeater Features:
  • Repeater callsign - NC4TV
  • Ground Elevation 692' ASL, near top of 160' monopole
  • Repeater input frequency - 434.000MHz (cable channel 59)
  • Repeater output frequency - 421.250MHz (cable channel 57)
  • Two five-element Yagi antennas fed with 7/8" Heliax
  • TX-RX Duplexer
  • Two International Crystal VSB filters (RX & TX)
  • Jerrold C6MII CATV modulator
  • M57745 20 Watt driver amplifier
  • Teletec ATV repeater 150 Watt power amplifier
  • P.C. Electronics ATVR receiver
  • ELKtronics Video ID unit
  • Microprocessor controlled ATV repeater controller/video switcher (10 video, 4 audio inputs)

• Photos of the Repeater Site:
  • The building which houses the repeater
  • A view of the tower at TV Hill
  • Another view of the tower (photo courtesy Charlie Durst NC4CD)
  • An enlarged view of the candelabra at the top of the tower
  • A closeup of the two ATV Yagis protruding from the edge of the platform
  • The equipment rack full of our repeater components (photo courtesy Charlie Durst NC4CD)

• Planned Enhancements:
  • Weather Radar (NOAA Doppler Radar)
  • 1.2GHz ATV Receiver
  • TVRO satellite receiver with 10' dish (on-site) for NASA Select
  • Tower Cam (Remote controlled tower-mounted color camera with pan, tilt, and zoom)
  • Links to other ATV Repeaters

A Second Triangle ATV Repeater?

In addition to the enhancements for the Durham ATV repeater, we are building a second ATV repeater, which will be located in Raleigh, NC. The Raleigh repeater will be a split-band repeater with receive inputs on 1.2GHz and 2.4GHZ FM, and transmit output on 421.250MHz VSB and 2.4GHz FM.  Both the Durham and Raleigh repeaters will be linked full time on 2.4GHz.

Both repeaters will transmit on 421.250MHz. However, the Raleigh repeater antenna will be vertically polarized, and the Durham repeater antenna will remain horizontally polarized.  The cross-polarization is expected to provide the necessary isolation between the two transmitters.

Triangle ATV Association Goals:

• Public Service operations
• SkyWarn - NOAA Weather Radar
• ARES - On-site damage assessment for the State and County EOC
• Educational purposes - TVRO satellite receiver on-site to provide "NASA Select" for Space Shuttle rebroadcast

Triangle ATV Association Meetings:

The Triangle ATV Association is not holding regularly scheduled meetings at present.  Specially scheduled meeting will be announced via the Association's e-mail list server.  To be added to the list server, send an email with the word "subscribe" (without the quotes) as the title to tri-atv-request@cs.unc.edu.

Contact Information:

The Association maintains an Internet e-mail mailing list that is used to send local area hams meeting announcements and miscellaneous ATV information.  If you would like to be added to this list, send your request to Nick K4NYW at nick@cs.unc.edu.

For specific questions about the Association, send e-mail to tri-atv@qsl.net.

A Basic Overview of ATV:

An ATV station does not have to be expensive.  Most hams already own many of the basic components required for an ATV system: an analog TV set, a VCR, and probably a video camera (camcorder).  With the ongoing switch to high definition TV (HDTV), many of these analog components can be had quite cheaply now.

Receiving 70cm Amateur Band ATV Signals:

Since the Triangle ATV Repeater's video and audio comply with NTSC standards, you can use a standard TV set for receiving its signal.  If it's a "cable-ready" TV, or if you have a standard VCR which can tune cable channels, simply connect a suitable outside antenna (see below) and tune to cable channels 57 through 60.  There are four ATV channels in the 70cm band:  421.250MHz, 427.250MHz, 434.000MHz, and 439.250MHz.  These frequencies correspond to Cable TV channels 57, 58, 59, and 60 respectively.  This is the least expensive approach to receiving ATV transmissions in the 70cm Amateur band.  (Please note that Cable TV channel frequencies are different than over-the-air UHF TV channel frequencies.)

Another approach involves modifying an over-the-air UHF TV to receive the 70cm Amateur Radio band where most ATV signals are found.  Many hams have re-tuned standard UHF TV tuners to receive 70cm ATV signals.  Many of the small portable TVs that have slide-rule type tuners are very easy to retune since they are tuned by a potentiometer that varies the D.C. voltage to a varicap diode.  You simply adjust the calibrate pot to "slide" the tuning range down where the 70cm band is located, just below UHF channel 14.

Still another approach is to purchase an ATV Downconverter, which is connected between the antenna and the standard TV set's antenna input jack.  The Downconverter tunes the appropriate 70cm frequencies and converts them to a standard VHF TV channel.

Antennas for ATV:

VCRs and most TVs are designed to receive TV signals from broadcast stations running RF power levels measured in hundreds of thousands or even millions of Watts.  The Triangle ATV repeater operates with 245 Watts Effective Radiated Power, so the antenna used for receiving ATV signals and the sensitivity of the ATV receiver are very important.  You will get the best results with a horizontally polarized, high gain beam antenna pointed toward the ATV repeater.  Trees, foliage, houses, etc. greatly absorb UHF energy.  When compared to FM voice systems with the same power, antenna, etc., an ATV receiver's sensitivity is reduced by 26 dB because the receive system bandwidth is increased from 15kHz to 3MHz.  With this bandwidth, the noise floor is around .8pV, so you can see that quality coax and high gain antennas mounted as high as possible are necessary to make up this difference compared to the DX you are used to with FM simplex.  When it comes to ATV, as well as most other Amateur Radio VHF/UHF communications, there is no such thing as "too much" antenna gain.

Antennas for ATV work must also have broad bandwidth as well as gain.  Most high gain Yagi types have only 1% bandwidth, or 4 MHz at 70 cm.  In ATV applications, this will give less gain and higher VSWR to the most important color and sound subcarriers - assuming that the antenna was cut for the exact video carrier frequency in the first place.  The best true reference for antenna gains and performance is the results of the various VHF/UHF Conferences' antenna measuring contests held annually and publicized in the ham magazines.  Advertising claims have become mostly wishful thinking and sales hype.  M², K1FO, and KLM manufacture excellent ATV antennas.    The so-called "quagi" antenna, with a quad driven element and a quad reflector, followed by a series of yagi-style directors, seems to be an easily constructed homebrew antenna popular among ATVers.  If you live close enough to the repeater you might get by with using a vertically polarized 440 MHz FM antenna.

Flexi-4-XL or 9913 style coax is recommended.  For runs over 100' you may want to consider investing in some good copper hardline or an antenna-mounted low noise preamp.  An antenna-mounted preamp can increase receive sensitivity by an amount equal to the coax loss.  Use type N connectors for all coax connections.  PL-259 coax connectors are not suitable for 70cm and above.

Transmitting ATV:

You don't need any kind of license to receive ATV.  However, you must have a valid Amateur Radio license to transmit.  Fortunately, even the most rudimentary Amateur Radio license currently being issued, the "Technician" license, will allow you to participate fully in this most interesting mode of ham activity.  The Technician exam is administered locally by several Amateur Radio clubs in the Triangle area, and an exam session is likely to be found within easy driving distance most weekends.  The test consists of 35 multiple-choice questions, and websites which allow you to take practice exams are plentiful.  Study materials from the American Radio Relay League, the national organization for Amateur Radio in the USA, can be checked out from almost any public library or purchased directly from the League.

Once you have your license, make contact with an area club and get some assistance in setting up your first station!

In 1993, QST magazine published a series of three articles giving a basic overview of ATV.  They can be read online through these links to the ARRL's website.  While these articles are somewhat dated now, they still provide some good background information:

• QST April 1993:  "Introduction to Amateur Television Part I" (PDF)
• QST May 1993:  "Introduction to Amateur Television Part II" (PDF)
• QST June 1993:  "Introduction to Amateur Television Part III" (PDF)

Is Digital ATV  ("D-ATV")  The Future?

Digital ATV can be complicated, confusing, and expensive.  There are several different and incompatible standards being used, but here are links to several newsletter articles from the Orange County (CA) Amateur Radio Club which help sort it all out:
• OCARC Newsletter TechTalk #74:  "Amateur Television (ATV) --The Digital Fork in the Road" (PDF)
• OCARC Newsletter TechTalk #75:  "Planning a Digital ATV Station" (PDF)

Links to Other Useful and Interesting TV Information:

• ANTA --ATV in France
• ATVS --ATV in Slovenia
• Amateur Television Network --streaming ATV repeaters on the internet
• Amateur Television Quarterly --the publication about the video aspect of Amateur Radio
• Baird Television --the Scottish pioneer of mechanical TV John Logie Baird
• BATC --ATV in Britain
• BRATS --an ATV club in Baltimore MD
• Decade Engineering --scan converters and video overlay generators
• DX Zone's ATV Page --ham radio ATV-related links
• Early Television Museum --a fascinating journey through the history of early TV technology
• Germany-Niederrhein ATV --ATV in Germany
• GTH Electronics --video equipment maker, great links page
• Ham-ATV --a Yahoo Group just for ATVers
• I-ATV --ATV in Italy
• LISATS --launch info ATV club at Kennedy Space Center in Florida
• Mirage Amplifiers --brick power amps for ATV, up to 100 Watts output
• Museum of Television --slick website that's interesting on several levels
• Narrow-Bandwidth Television Association --a British organization recreating the mechanical TV experience
• North Country Radio --inexpensive ATV transmitter and downconverter kits
• P.C. Electronics --the leading supplier of ATV equipment
• P's and Q's of Video Signals --a primer on the "P System" of rating video signal quality
• The Philo Farnsworth Archives --official family site of the boy who invented electronic television
• TV Technology --the digital television authority
• W3XK --the TV station of American TV pioneer Charles Francis Jenkins

Images From Television History:

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Thanks to the kind folks at QSL.NET for hosting our web page. Last updated July 6, 2009 by K3VSA. 73 es tnx for watching! Please e-mail comments, corrections, or suggestions about this web page to  tri-atv@qsl.net

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