Originally Posted by BobTurner
Crummy SWR doesn?t just mean less power to the antenna. It also means significant power flowing back into the transmitter, where it creates all sorts of trouble.
As a guy who has designed a lot of circuitry, waded around in waveguides, magetrons and other esoteric hardware for a long time, I think I've got the subject down pretty well. It has been my experience that vswr is rarely related to "bad transmitter audio", could be, of course. But it would be a rare instance.
A more likely cause, and one I ran into often, was off frequency receivers and/or transmitters. Channels are very tight now-a-days. A particularly vexing combination to troubleshoot is a tx leaning one way and the rx the other way. Both stations work ok except the combination, and often only in one direction because one unit is more bandwidth tolerant. This result is consistent with the OP's description.
To the OP: If this get to be more than that single instance, I would check the transmitter frequency. All later aircraft radios use synthesizers. So, freq tolerance checks are simpler. Checking one freq checks them all.