--- In Repeater-Builder@yahoogroups.com, "rfburnz" <[EMAIL PROTECTED]> wrote: > > The general consensus with phase modulated rigs is to use > discriminator audio thru the controller then into the exciter. the > initiating transmitter (into the rptr rcvr) already preemphasized > audio, this then is de-emph in the final recvr (after being > transmitter from the repeater). > Transmitters that employ a true FM modulator require a pre‑emphasis > circuit before the modulator; the true FM modulator doesn't > automatically pre-emphasize the audio like a transmitter that uses a > phase modulator. > > here's a good article to read: > http://www.repeater-builder.com/tech-info/flataudio.html >
Thanks for your reply. Correct me if I am wrong, but in order to make the audio sound "normal" through the Phase Modulated transmitter I have to engage the de-emphasis network on my controller circuit board. If I feed flat discriminator audio into the PM exciter it ends up getting double-emphasized which makes the audio sound strange. So my question is specific to the GE Mastr II. I suspect that the receiver setup in a stock Mastr II de-emphasizes the audio because it's designed to work with the PM exciter which adds emphasis as a function of how it modulates. Further I suspect that the GE Mastr II FM exciter is designed to be a drop-in replacement, which leads me to believe that the FM exciter board has pre-emphasis circuitry on board. I've found the LBI that describes the FM transmitter and it does appear to run the audio through a pre-emphasis network. I am pretty new at this so I'm not very good at looking at the schematic and figuring out where to physically inject flat audio into the FM exciter to skip the pre-emphasis network. I am wondering if anybody familiar with the GE Mastr II and the FM exciter has done this before to run the repeater with completely flat audio? Thanks Mark Hagler KK7U Seattle
