HAM TV Pictures
From The WB7TJD Wiki
Ham TV Pictures received in east Mesa
These photos were taken off of the television screen as Tim Campbell was watching HAM TV reception from the White Tanks 1.2 GHz ATV repeater over 50 miles away. Several contesters had HAM TV gear with them in the Harquahalas during the 10 GHz contest Saturday, August 21st, 2010.
Tim used his 1.2 GHz antenna and down converter tuned to standard TV channel 7 from his home near Southern Ave and 86th Street in east Mesa. The area is between Ellsworth and Crismon, and between Southern Ave and the US 60 freeway.
The output of the repeater is 300 watts at 1252.25 MHz NTSC TV video carrier.
The White Tank Mountains are north of due west at a range of 55 miles, going over Glendale from Tim's location, versus a distance of approximately 27 miles south of due west to South Mountain, which hosts the Phoenix broadcast TV towers. Before commercial television went digital, perhaps the best known low-power TV station in Phoenix was Channel 27, which was a translator for a Prescott station on Channel 7. This station was perhaps running on the order of 1kW on its video carrier.
The pictures we see here are from a station that is running a third of the power, from twice the distance, and probably being received on equipment that is more sensitive than the standard television receiver.
HAM TV uses the same transmission standards as pre-digital analogue broadcast TV. The channel width is 6 MHz because the repeater is using vestigial sideband, which includes the full upper sideband, carrier and approximately 1 MHz of the lower sideband, the inclusion of which helps reinforce synchronization of the picture. Audio is carried on an FM subcarrier, which is amplitude-modulated onto the video carrier, and because the lower sideband is truncated, only appears on the upper sideband, 4.5 MHz above the video carrier.
--Thanks Bil, K1ATV for these pictures.
