'49 Admiral audio problem

[kbmuri]

Sticking with the Rat Shack receiver as my Video/Audio source. Much more convenient for the source to be something the size of a coffee mug vs the size of a briefcase.

Receiver connected to matching transformer with 1 foot of coax. Transformer to antenna terminals. TV on its side, receiver placed on chassis right side (now top). DVD playing same (obnoxiously loud music) intro-screen loop. Excellent video as usual from haunted roundie. Generator connected directly to antenna terminals via alligator-clip coax probe. Counter alligator clip to chassis ground and induction-coupled to generator (alligator clip attached to coax insulation of generator probe). TV set to channel 3.

Generator unmodulated, sweep from 50MHz to 70Mhz:
56.7 MHz-, normal video.
56.7 MHz, just notice some effect on picture quality
56.7-58.5 MHz, picture fades smoothly to black
58.5 MHz, black screen.
58.5 - 63.1 MHz, black screen (Zero-beat is in there somewhere, can I narrow this down?).
63.1 Mhz, just notice change in black screen
63.1-64.5 MHz, smooth fade back to normal video
65.5 MHz+, normal video

Tone modulation applied to generator (500Hz). Sweep back down the range:
64.9 MHz, first notice audio at 1/4th volume setting (comfortable level)
63.90 MHz, first maximum tone level, fairly loud
63.65 MHz, very noticeable lull in sound, near quiet
63.20 MHz, 2nd maximum tone level, probably louder than 1st by a little bit.
61.50 MHz, Last noticeable tone
61.60 MHz-, silence

59.27 MHz, Maximum point that tone bars on screen completely override normal video. Elsewhere in the sweep, at least some video is apparent.