Winter 2007 Issue

Microwave ATV – A New Approach!

This article was originally presented as a paper at the 2006 Microwave
Update in Dayton, Ohio and published in the Proceedings. In it W3HMS challenges the reader to consider other frequencies, such as 3480 MHz
and 10 GHz, as possible alternatives for ATV use.

By John Jaminet, W3HMS

ATV picture at the author’s QTH.

The author in front of his ATV ham station.

Amateur Television (ATV) has, since its inception in the 1950s, used the 420–450 MHz band for both simplex and in- band AM repeaters. This was necessary in the early days as little equipment operated well above 2 meters and reception was often accomplished using converted UHF TV tuners with poor sensitivity. The pictures were often marginal, with rolling, without color, and without sub-carrier sound. Those close to repeaters will argue differently, but in the fringe area where I found myself, the best pictures were rather pathetic by the commercial color and sound standards of the day. Sound was often transmitted on 2 meters, which did offer two-way discussion of the picture on the screen. Sub-carrier sound as the broadcasters did it was the exception rather than the rule, and sound-on-carrier required an additional receiver. The transmitters classically used crystal signals doubled and tripled to the output frequency, often 439.25 MHz, using cathode AM modulation.

A Visit to Switzerland
In the fall of 1997 I found myself at the QTH of Michel, HB9AFO, near Lausanne. During one evening in his shack I had the pleasure of seeing a rock-solid 1255-MHz FM ATV picture at 18 miles between Switzerland and France. It was great—like a painting on the wall—except for the plume of smoke from his pipe coming across Lake Geneva in France! This was the day that I knew there must be a better way . . . and there is! It is FM and the microwave bands.
Another reason why I visited HB9AFO was to see his world-class 10-GHz ATV equipment. He and his partner then held the world DX record at about 410 miles. I was impressed by the use he and colleagues made of Ku-band satellite components such as LNBs and antennas. Indeed, F6IWF had developed a modification for a popular LNB that brought all the power of engineering and production for a mass-produced item and gave hams a super-performing LNB for relatively low cost. The same was true for 60 cm and larger offset dishes.

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