WELCOME TO FAST SCAN AMATEUR TV

Fast Scan Amateur television has been around in Ham Radio for over 70 years. Articles about Hams experimenting with motor driven scanning disks appeared in QST as early as 1925. Most modern Fast Scan Amateur Television, or ATV, uses a transmission format fully compatible with video equipment designed for the individual consumer market. The video is amplitude modulated; the audio is frequency modulated. This means that a Fast Scan ATV picture displays full motion, has a simultaneous sound channel, is usually in color, and has excellent detail just like commercial television. Fast Scan TV is sometimes transmitted using a frequency-modulated format for both the video and audio, which can also be received using readily available equipment.

Amateur television offers a major advantage over broadcast TV though, in that we can communicate interactively or two ways. Amateur television Hams have been communicating in round table nets for years, long before business and industry discovered the benefits of interactive video, or, "teleconferencing".

Because the signals occupy several Megahertz of bandwidth, the FCC does not permit Fast Scan TV on bands below 420 MHz. Most ATV activity is found between 420 - 440 MHz. ATV is also found in the 900 MHz, 1200MHz, and 2.4 GHz bands. There are also ATV repeaters and linked systems that operate entirely in the microwave bands. These frequencies generally limit FSTV activity to line-of-sight with extended coverage possible when ducting conditions exist or repeaters are used.

Any licensed Amateur Radio operator can operate ATV.

In keeping with the ham tradition for both public service and inventiveness in communications, ATVíers have been using their live action video systems in many exciting applications. The Southern California ATVíers annually help coordinate and monitor the Tournament of Roses Parade and local marathons. ATV is used to aid public agencies such as the Red Cross in "damage assessment" during floods or forest fires. During the Christmas season, amateurs have taken their systems into hospitals to permit children to see and talk with Santa Claus over live TV. Amateurs have transmitted ATV from Civil Air Patrol planes, hot air balloons, and rockets. ATV has been used in radio-controlled airplanes and robots to provide feedback to the operator. The FCC permits ATVíers to re-transmit the spectacular NASA space shuttle video, and FSTV is a big part of the ARISS project that links students in classrooms with astronauts in orbit. Formerly called SAREX, Space Amateur Radio Experiment and now called ARISS, Amateur Radio on the International Space Station.

Our purpose is to promote, advance and encourage FSTV, serve the public, promote goodwill and further the state of the art of communications. Like many Amateur radio clubs we at AATV are a non-profit organization (5013C). AATV has a web page at, www.w7atv.com, where you can find photos, the club calendar and other ATV related subjects. Currently we hold monthly meetings on the second Sunday of the month at 2:00 PM at the Red Cross building, 6135 N. Blk Canyon Hwy. We also hold weekly nets on Wednesday and Sunday evenings at 7:30 PM. These nets use both the video repeater and the AATV voice repeater, 146.840 (-) 162.2pl. We encourage anyone with an interest in ATV to join us during these nets or at our meetings, whether you have video or not!

 

Receiving the W7ATV AM Repeater

Receiving ATV in the Phoenix area may be as simple as connecting a vertically polarized 430 MHz antenna to your cable ready VCR or television. The output of our AM ATV repeater, W7ATV, is 421.25 MHz, (AM) which corresponds to cable channel 57. The repeater antenna is vertically polarized. If you live in the Phoenix area and have line of sight to the top of Shaw Butte, (where, 7th Avenue would cross Cactus), you should be able to receive the W7ATV repeater. Reports of reception within 4 - 5 miles with simple Ďrabbit-earsí have been received. Simply tune your cable ready television or VCR to cable channel 57 and connect a vertically polarized antenna in place of your cable connection. For non-cable ready TVís, the bottom edge of channel 14 is at 470 MHz. Thatís a little above the repeater output of 421.25 MHz. Some thumbwheel tuners on older VCRís tune down far enough to receive the repeater, but digital units usually donít allow that flexibility. Some portable and handheld TVís such as the Sony® and Radio Shack® units reportedly will receive the repeaterís 421.25 output. This repeater also has an output of 1241.25 AM which does not correspond to a broadcast or cable TV channel. To receive the repeater on this output requires a commercial receiver or downconverter. See the supplier list at the end of this article. A second ATV repeater is located on the White Tanks mountains west of Phoenix. This repeater receives on 421.25 MHz (AM), the same frequency as the output of the Shaw Butte repeater, and transmits on 1289.25 MHz (AM).

 

Receiving the W7ATV FM repeater

The AATV FM repeater has an input of 1265 MHz, and an output of 916.384 MHz. This repeater is off-line for upgrades. To receive this repeater requires a 900 MHz receiver. A C-Band Television Receive Only or TVRO receiver is an FM receiver that generally obtains the signal from the LNB, (Low Noise Block downconverter), at 950 to 1450 MHz. Some TVRO receivers tune from 900 to 1400 MHz which is low enough to receive the 916.384 MHz repeater output, although these units are hard to find. Another alternate receive setup uses a Gemini "Rabbit®" (AM) and an older TVRO, (one which used an LNA). The output of the Rabbit is fed into the TVRO which has a 70MHz IF strip to demodulate the FM signal. A pre-amp may be necessary with this setup due to the weak receive of the TVRO. Look for the loop connection on the back of LNB type receivers and a 70MHz input on the LNA type. One of the LNB TVRO units can be used to monitor the output of your 1200 MHz FM transmitter and also function as a simplex 1200 FM video receiver to enable you to work ATV DX!

 

Transmitting

Inputs on the W7ATV Shaw Butte repeater are at 434.00 MHz AM, 1265.00 MHz FM, and 2.434 GHz FM. Minimum equipment for the 434.00 MHz input is considered a 1 watt transmitter and either an amplifier or as much antenna as is affordable. If an amplifier is used it should be class A or class AB. A Class C amplifier is not acceptable. Make sure the amplifier has a SSB position. Most ATV transmitters for 430 and 1200 MHz are commercial units. Some kits are available, and a few are home brewed. The 2.4 GHz transmitters in use are usually modified Wavecom® type units. These units are inexpensive, readily available and easily modified.

This is also not the place to skimp on coax. At 430 MHz and above with low power levels, cable loss can be quite high, especially for long cable runs. Good low-loss coax such as Belden® 8214, 9913, or 9914 are recommended. Many of the techniques that apply to QRP also apply to ATV.

Both our AM and the FM repeater use vertical antenna polarization. Yagi and corner reflector antennas are fairly easy to construct for the 430 and 1200 MHz bands. Yagi and dish antennas that were used for MDS TV can be modified for the 2.4 GHz band.

See the supplier list at the end of this article.

While operating a video repeater, The transmitting operator monitors the talk-back frequency that is in use for the repeater. The W7ATV repeater talk back frequency is our voice repeater, 146.840(-) with a pl of 162.2. This allows a viewer to interact with the transmitting station and also ensures that an operator is not "Broadcasting", which is not allowed in the amateur service.

If you have a question about ATV, or if you would like some help in setting up a station, transmit or receive, voice your request at any time on the ATV repeater, 146.84 (-) PL 162.2. AATV Club members are always willing to help. If you would like help to check your location for transmit/receive ability, please ask. Some members have mobile transmit and receive capability and are eager to check your area for "hot spots." We also have software "Topo" programs that can plot your intended path. Join us and "SEE" what youíve been missing!

 

ATV Publications

ATVQ Amateur Television Quarterly 5931 Alma Dr., Rockford, IL 61108 www.hampubs.com

CQ-TV British ATV magazine

TV-Amateur (German) subscription available at ATVQ

Repeater! European ATV / mmwave magazine

 

 

Suppliers of ATV and Related Equipment

ATV Research Inc. www.atvresearch.com/ ATV equipment

Bomar Crystal Company. www.bomarcrystal.com/ Crystals

Cable X-Perts Inc. www.cablexperts.com/ Coax Cable and RF Assemblies

Down East Microwave Inc. www.downeastmicrowave.com/ UHF/Microwave parts & modules

EZATV. www.4atv.com/atvprod.htm 23 & 13 cm amplifier and preamp kits

Hamtronics. 65 oul Rd.,Hilton, NY 14468-9535 www.hamtronics.com/ Commercial & Amateur Equipment

International Crystal Manufacturing Co., Inc. www.icmfg.com/ Crystals

Intuitive Circuits Inc. www.icircuits.com/ Video overlay, controllers and specialty items.

M≤ Antenna Systems. 7560 N. Del Mar, Fresno, CA 93711 www.m2inc.com/ 1.5 to 3000 MHz Antennas

Mirage Amps. www.mirageamp.com/ Amplifiers

Pacific Wireless 2844 Mar Vista Drive, Suite 101, Aptos, CA. 95003 2.4 & 5.8 GHz Antennas

Pauldon Assoc. 210 Utica St. Tonawanoa, NY 14150 (716) 692-5451

PC Electronics 2522 Paxson Ln. Arcadia, CA. 91007-8537 (818) 447-4565 www.hamtv.com/ Suppliers of Amateur Television Equipment

Radio Ware. www.radio-ware.com/index.html ATV transmit and receive equipment and kits

Super Circuits. www.supercircuits.com/ Video Cameras, Transmitters and Recorders

Decade Engineering 5504 Val View Drive SE, Turner, OR 97392-9517 video text overlay

SHF Microwave Parts Co. www.shfmicro,com/ Microwave Parts for Radio Amateurs and Experimenters

Wyman Research Inc. 8339 S. 850 W., Waldron, IN 46182-9644 www.svs.net/wyman/ ATV equipment including kits.