Hello Bob, so tell me what kind of buffering Op Apm are you using in you controllers? I've used the LM324 quad opamps but I can still tell I my audio sound different comming out of my HT than the repeater. I am taking my audio directly off the discrimanator going through a opamp with de-emphasis then to the mic input. I still don't like the way it sounds. I'm using a motorola mitrek mobile for a repeater. Are that PM or True FM?
May be we can converse over the phone? 785-483-3377 Eric (N7JYS) --- [EMAIL PROTECTED] wrote: > Hi Eric, > As we're finding out via experiments here, there are > other interesting > sources of distortion (especially in older > technology repeaters) besides those > created in the audio circuits. > > For example, PMs built with a varicap and LC > resonant circuit are based on > the assumption that the phase shift of the circuit > is linear as the varicap > voltage is changed. This isn't true because the > phase shift follows a tangent > curve, thus you get more distortion at the ends of > the curve than at the flattest > part. > > Similarly, quadrature detectors use an LC resonant > circuit and thus add > distortion of their own to the recovered audio. > Since the distortion occurs at the > high end of the frequency response, tapping into > this kind of discriminator > for your audio results in more distortion, not less, > than tapping into the audio > after the de-emphasis. That's because the > de-emphasis rolls off the > distortion products. > > A surprising amount of distortion comes from > multiplier stages that are > mistuned. > > And, we've previously talked about the distortion > that comes from the audio > 'blobs', especially from the soft action of some > limiters. > > For these reasons, I don't get too particularly > worried about adding a couple > of parts in the external audio chain - - especially > since I'm in the > controller business... :-) > > 73, > Bob > > > Bob Schmid, WA9FBO > S-COM, LLC > 970-416-6505 phone > 970-419-3222 fax > www.scomcontrollers.com > __________________________________ 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/
