[Electronic M]

Hooked directly to a TV you may have TOO MUCH signal power for the tuner to handle. With a direct connection start with minimum output power and slowly increase it until it is decent, if it even needs any increase (which it should not). The pots I mentioned and named are on the front and back panels and can be adjusted without opening the unit....

Try again with lamp cord and cut to the appropriate length for the channel you are going to use.
I do NOT have an antenna analyzer either....The math process Shango uses was sufficient for me to cut antennas that work well. Cutting them to proper length is rather important...You will get VERY little transmission range if you use an antenna that is not tuned to the station you wish to transmit on (case in point the crappy results I got with an off the shelf UHF/VHF all band antenna). Also make sure your dipole is high up in the room you are using it in, the two ends of the dipole are pointed away from each other, the dipole leads are taught, and the antenna does not sway, vibrate or move in any noticable way.

Lets not worry too much about UHF for the moment. UHF is much more finicky to transmit and receive on, so lets first get good results with simple VHF frequencies and methods to prove your modulator is working before working with UHF.

By the way do you know what RF channels (as opposed to those stupid, fake 'virtual channel numbers') your regions DTV stations are transmitting on? That is important to know. If you transmit on the same channel as a regional DTV carrier your modulator will likely be drowned out by the DTV station, or at least severely interfered with by it (or if you look at it another way you may be jamming your neighbor's attempts to receive that DTV station, which could bring the FCC to your door). If you can, also avoid channels next to DTV stations (at least until you confirm your modulator is good) as adjacent channel interference may result.

Also the test TV is important. I'd test the antenna with a newer solid state TV (preferably a portable that you can walk outside with to check the signal range once you get it right) if I were you. It is hard to be certain of the calibration and performance of the receiver sections of older TVs. If it works with a newer set, but your old one is not liking it then that old set will need some work.

Remember over modulation and under modulation can cause many strange effects just as too much signal or too little signal can cause undesirable effects.