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Hi Everyone!
Thank you for your thoughts on the noise issues that I have described in my 1966 Zenith. I wanted to let people know what I have discovered in the troubleshooting process and what I think is the solution.
I'll start by letting you know what I forgot to mention... I live in the metro Atlanta area and there is a low power VHF station that broadcasts on channel four. I live close enough to the antenna that I believe this was a big part of the picture noise I mentioned. As a test, if I disconnect the balun, I can see a snowy color picture, with sound, on channel four. Even channel three has some residual content that leaks through. I had been using an inexpensive RF modulator (Phillips brand) and it works perfectly on a 1985 Magnavox which has one of the early all digital tuners. However on the 1966 Zenith, the separation of channels isn't quite as distinct.
So- I decided to buy a Blonder - Tongue modulator and try to use other VHF channels. I found one of the agile series modulators on eBay for a fair price.
I bought a model AM-60-550-option 4. This version has a digital display on the front for changing the frequencies instead of using DIP switches which makes this very user friendly. It is in "like new" condition.
So what I discovered is that given where I live and the TV I am driving a signal into, it has worked out very well if I use the upper VHF frequency range (7-13),
specifically, channels 8-11 seem to bring in the best picture. Using this broadcast quality of RF modulator, I found the best channels to use and all of the noise has gone away. It really is an amazing improvement! So I settled on channel 11 but could have chosen others.
I also experimented with feeding the Zenith directly into the chassis with IF instead of RF through the tuner. That does work very well, but I don't know if it really makes the picture better. In reality, using the fine tuning control in the TV can help in dialing out the buzz and softening the picture in a pleasing way.
So I have stayed with using the RF out of the Blonder - Tongue on VHF channel 11 and it is great! Investing in this professional modulator has worked exactly how I had hoped and it is very flexible for RF or IF output.
All the best-
Dave
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