Another source of TVI from local oscillators is the original version of the Heathkit SB-110. The heterodyne oscillator operates around 42 MHz when the 50.0-50.5 MHz segment of the 6 meter band is selected. I used to use this rig when I lived near New York City and never had any problems other than some audio rectification RFI into a neighbor's stereo. When I moved to South Jersey in 1992, I discovered that this rig would put a herringbone on channel 6, even in receive mode. A strong second harmonic of the oscillator at 84 MHz (right in the middle of channel 6!) was being radiated by my antenna. The TVI extended over a considerable distance, as I walked down the road with a small portable TV set tuned to channel 6 while the SB-110 was turned on and receiving. My house in South Jersey is within the Grade B contour of WPVI-TV, the ABC outlet on channel 6 in Philadelphia.
Heath later added a low pass filter after the heterodyne oscillator and made a few other changes to tame this rig, renaming it the SB-110A. But it was discontinued after a few years. Phil K2PG
