--- [EMAIL PROTECTED] wrote: > Anyone have a good design for a high quality Audio > circuit to put in > between the discrimanator and the TX audio? I not > looking for the > typical repeater controller design as I've been > there and done that. > I want the highest posible quality of audio > reproduction I can get. > Thanks for you time and reading this. > > > 73's > > Eric (N7JYS) >
If you want the highest quality, that would probably translate to least amount of change; IOW, as close to original as possible. If you have a very good (flat) discriminator, and a very good true FM modulator, the simplest way is to connect the disc to the mod through what ever level amp/pad that needs to be to match levels. This should give you the "best sounding" audio. However, there are a couple of problems with doing this. The main problem is that on noisier signals, the high freq noise component from the disc will modulate the TX with a wider than normal signal. This may cause your TX to occupy a wider than necessary bandwidth, which could interfere with adjacent channel repeaters. The other problem is that an overdeviated signal entering your RX will leave the TX overdeviated as well, causing wider than normal bandwidth also. The solution is to install a "clipper" to limit the deviated bandwidth to 5KHz, and an LPF of around 3 to 4 KHz or so, to limit the upper modulated frequency. If these are chosen properly, it will be hard to tell that they are in the circuit: The clipper will only function on overdeviated signals, and the LPF will take out high freq noise, since most radios don't TX anything above 3KHz anyway. Joe __________________________________ Do you Yahoo!? Yahoo! Small Business $15K Web Design Giveaway http://promotions.yahoo.com/design_giveaway/ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
