Re: Assistance with modulator design
Hi Matt,
I would use a TDA5660 chip (see attachment). This was designed to deliver AM vision with negative modulation and FM sound. Since the FM sound is generated by an LC tank circuit it can deliver the 6.5 MHz OIRT sound-vision spacing easily. The RF channel frequency can be run with an LC circuit also, so any frequency can be generated, or you can try to find a suitable crystal for the vision carrier. I have found though that an LC circuit is absolutely fine and does not drift. I have had such a circuit in operation here on channel E3 at around 56mc and it has been running fine over many years.
I might still have an empty PCB board around here that I had designed for this chip years ago if you are interested send me a PN. I can also build a modulator and send you the board. This might take a few weeks though. I can also send you the project data it was made with the Eagle CAD software.
Cheers
Semir
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