Project:

Crossband ATV repeater.

Designer(s):

N8UDK / N8QPJ

Description:

The D.A.T.S. N8UDK ATV repeater is located on the top of a sixteen story building at Fourteen Mile Road and Main Street in Clawson Michigan. It has been fully operational since May 1995. What's an ATV repeater? In a nut-shell an ATV repeater allows people (who have a license from the FCC) to video conference far distances reliably. Unlike Desktop computer video conferencing which is normally no better than 15 frames per second, ATV is broadcast quality 30 frames per second. This is accomplished through the use of radio frequencies (RF) instead of telephone or ISDN lines. The repeater's input is 439.25 MHz AM (LSB) and the output is 1253.25 MHz AM. The cross banding is useful because it allows users to see their own video coming back from the repeater. There is now also a 32 watt 434.00 MHz AM output (tune your TV or VCR to cable ready channel 59 to receive it). I'm sure you've seen the many benefits of video conferencing but there are also many "bells and whistles" to play with also. Via two 440 FM control frequencies you can control four cameras on the top of the building. From the comfort of home view the inside of the repeater room with an indoor pan and tilt camera with on screen telemetry which shows information like room and amplifier temperatures, audio and video sources selected, etc. See your signal strength, turn on lights, watch the repeater graphic ID, and other AC devices. There is even a 360 degree pan / 180 degree tilt rotor with a high resolution color camera and a low light, high resolution black and white camera attached. Both have remote controllable 10x zoom lens. We’ve viewed approaching storms, forth of July fire works (from five cities), fires, the beautiful night skyline, the repeater antennas, and other interesting sights from a very unique perspective. We've also added a Gekco colorbar generation with a newly designed DTMF decoder board so the colorbar pattern's can be cycled remotely. In addition a rotor was added to the 2.4 GHz receive dish antenna so anyone with 2.4 GHz transmit capability can remotely turn the antenna to their location. NASA shuttle missions are also rebroadcast. If you can’t watch you can listen with a scanner tuned to 1257.75 WFM. The shuttle is uplinked via 2.4 GHz from N8UDK's QTH. Special note: FCC rules don't allow the 434.00 output to be used to repeat incoming video/audio but all the sources originating from the repeater site can be transmitted on this frequency.

Some Technical Information:

P.C. Electronics manufactured the transmitter and receiver. The reason for 439.25 MHz lower side band input (LSB) as opposed to the normal upper sideband was to cut down on repeater link interference. Most users transmitters transmit both sides so no addition equipment is required by them. The 1.2 GHz amplifier is made by Down East Microwave. The average output power is about 25 watts. At the heart of the repeater is my third generation controller. Its' intelligence comes from three Parallax Basic II Stamps which communicate with each other and do their processing in parallel. The controller has eight video inputs, six audio inputs, three temperature inputs, 4 AC outputs, a digital voice recorder, custom DTMF decoder, MAX455 video selection IC, ID8 CW generator, Elktronics ID board, BOB-1 video character generator board, and two sync detect boards. All features of the repeater are fully remote controllable via DTMF commands. On air voice messages notify you when an ATV signal is coming in, a problem has occurred, etc. The on air messages and telemetry overlay make the repeater really user friendly!

Hardware (the bigger pieces):

• Comet 1.2 GHz Antenna GP-20 (vertical polarization)
• DCI Vestigial Sideband Filter 1253.25
• DownEast Microwave 1.2GHz 40 watt amp
• PC Electronics ATVR-4 ATV receiver
• Slot-rib cage antenna (horizontal polarization)
• ICM FL407 Vestigial Sideband Filter 439.25 LSB
• PC Electronics RTX 23 ATV transmitter
• Custom controller
• Kenwood TM441a radio with CTCSS decoder
• ADI AR-446 radio with CTCSS decoder
• DCI 440 FM filter
• Yaseu 5400B az/el rotor
• Several B/W cameras
• JVC TK-885U color camera
• PELCO EH3512 outdoor camera housing
• Panasonic WV-BP314 B/W hi-res camera
• 2 PELCO 4718-2 outdoor camera housing
• Rainbow H10X8MEA II Zoom lens
• JVC TK-885U color camera
• PELCO 4718-2 outdoor camera housing
• Rainbow S10X8MEA II Zoom lens
• PC Electronics one watt TX70 transmitter board
• Teletec 440 AMP
• Gecko colorbar generator

Hardware Sources:

• P.C. Electronics (626) 447-4565
• ATV Research (800) 392-3922
• Parallax (888) 512-1024
• DCI (306) 781-4451

Conclusion:

I can't even begin to guess how many hundreds of hours has gone into this project. It wasn't cheap and certainly not easy but the rewards of designing, building, testing, and finally using this ATV repeater is the essence of what amateur radio is all about. Getting there is half the fun!

- Chris Oesterling N8UDK

Fig 1.0 - "The Clawson Manor" (Clawson, Michigan) home of the N8UDK ATV repeater.

Fig 2.0 - The ATV repeater.

Fig 3.0 - The ATV repeater controller.

Fig 4.0 - Three of the outdoor cameras (front two on pan/tilt rotor).

Fig 5.0 - 439.29 input / 434.00 output antenna (horz) and 1253.25 output antenna (vert).

Fig 6.0 - Received 1253.25 transmission of the on-screen repeater telemetry overlaid with the repeater room camera.