FONER%MIT-OZ@MIT-MC.ARPA (Leonard N. Foner) (09/05/85)
If you're not a hardware person, you might as well stop reading right now. This is being sent to the above strange combination of lists because I have no access to UUCP's net.electronics. If some kind soul could forward this message there as well (once only!), please do. I'm going to be driving a large hunk of coax with taps off it with FM multiplex stereo. The cable already has normal video RF on it; I intend to modulate in the normal broadcast FM band, between channels 6 and 7 (88 to 108 MHz). The idea is to have a private FM stereo network that anyone with an FM receiver can listen to off the cable (analogous to cable TV, which is already on the coax). Unfortunately, I'm not an RF engineer, and my interest in *analog* high speed circuits was a) as a hobby, and b) quite some years ago. Hence, I'm very out-of-date on how to drive such a beastie. There *must* be a better way than the many-discrete-components ideas I can generate. What I want are references to schematics which would show how to do this. The lower the cost per transmitter, the better. What with stereo FM on videotapes now, it's possible that someone's made a chip to do the modulation, now that consumers might be generating FM. (I *know* the demodulators are a dime a dozen. This is different.) If there does not exist a chip around somewhere, I'd appreciate pointers to recent articles on building cheap stereo FM transmitters. The ideal transmitter would be one whose transmit frequency can be programmed with a DIP switch (i.e., a synthesized transmitter that divides down the carrier and PLL locks it to a crystal). As a part of that last piece, I'd love to hear about divide-by-n chips that are programmable from 1 to 256 via some eight-bit input, and can divide down an input frequency of 110 MHz or lower. If no such exist, I can take a slower part and put a fast flipflop in front of it, hence making even 50 or 25 MHz parts usable but inferior to one that's really fast enough. (This may not be a big problem, though, since 64 different frequencies is plenty given recommended transmitter spacing and the width of the band.) This *must* be a solved problem. I'd hate to reinvent the wheel, whatever I do. Can anyone point me to the relevant literature? Please reply directly to me, since I'm not on all of the above lists, and hold CC'ing the list unless you think it's of general interest. Thanx much! <LNF>