UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Multi-Channel VHF Modulator Design

flyback · 28th Feb 2005, 5:57 pm

Hi all,

I agree with Darius about the Electrolytic as a coupler and the Bias de-coupling, I use Tantalums in my circuits.

Darius, the Bias pot will set the "resting" level of the sound carrier(which is really coming from a vision modulator with it's clamp overidden), with it you can set the ratio of the sound to vision carriers correctly.

On Domino I did not provide two L/R inputs for sound, I assumed only mono vintage material would be played, most Vintage DVD TV stuff is mono!.

I have never seen/heard the need for a 3.5MHz filter on the video feed, your video should be band limited to ~3.0MHz, is this somthing that you have found is a problem, maybe with 405 line VHS playback?.

Malcolm

28th Feb 2005, 5:57 pm	#24
flyback Retired Dormant Member Join Date: Apr 2003 Location: Swindon Wiltshire Posts: 26	Re: Multi-Channel VHF Modulator Design Hi all, I agree with Darius about the Electrolytic as a coupler and the Bias de-coupling, I use Tantalums in my circuits. Darius, the Bias pot will set the "resting" level of the sound carrier(which is really coming from a vision modulator with it's clamp overidden), with it you can set the ratio of the sound to vision carriers correctly. On Domino I did not provide two L/R inputs for sound, I assumed only mono vintage material would be played, most Vintage DVD TV stuff is mono!. I have never seen/heard the need for a 3.5MHz filter on the video feed, your video should be band limited to ~3.0MHz, is this somthing that you have found is a problem, maybe with 405 line VHS playback?. Malcolm