My AT-600 ProII does the same thing.? It is not going to bypass because the SWR is good, but signal levels are down 10 dB or more on receive.? IF I go to a different frequency and retune, the signal levels come up.? I am using it remote with a 25' unshielded cable for control.? I have ferrite clamp-ons on the control cable at the antenna, but my suspicion is that RF on the control cable is interfering with operation.
