I’m looking for some help on checking if my understanding of FM audio (de-emphasized, pre-emphasized and flat) is correct. I’ve had some problems on figuring out why two repeaters that are linked together have poor audio when a field user is on one repeater and another field user is on the different repeater. I’ve sketched out an audio block diagram to try and visualize how the audio characteristics are being passed through the system. To highlight, the repeater system consists of two repeaters where one is VHF and the second is UHF. They are linked by RF with an extra transceiver on each controller port, that passes audio on a 220 MHz frequency from site to site. My understanding is that a user radio’s will have a pre-emphasis circuit when transmitting and a de-emphasis circuit when receiving (referring to normal HAM grade transceivers such as Yaesu, Alinco, Icom, Kenwood, etc). This is what happens when two users are transmitting by simplex. User A transmits, his audio is then pre-emphasized and transmitted, user B receives his transmission where his radio de-emphasizes the audio and is presented to user B. With this understanding, I’m assuming the correct thing to do is to keep audio passed through the repeater controller and link transceivers completely flat. This means that the audio being presented on the receiver has the exact same characteristics as when it is passed to the repeater transmitter. The interface or link transceiver will not shape or “touch” the audio as its being passed. If this was the case, I see where it could be possible to de-emphasized or pre-emphasize the audio twice. If my understanding is correct, each repeater and the controller should be configured to pass “flat” audio and basically allow the user in the field to handle the pre-emphasis and de-emphasis. Could someone tell me if my understanding is correct and if how I have sketched my audio block is correct?