Due to the latest 10 and 6M band openings, it is the first time I tried ssb. I am having "warbling" rx/tx audio on 10 and 6M. After a search, I saw the thread "distorted audio on 6600" and K2RB's post at the end about the 10Mhz reference. This mirrors my symptoms. His solution of Auto only temporarily seemed to clear up the audio with the external reference disconnected. I use the external 10Mhz ref from Leo Bodnar's GPSDO on lowest amplitude setting about 1.2v p-p measured at radio connected through a 30' RG-174. I saw the spec (1 to 3v p-p sq wave) for the min and max amplitude. Its a "square wave" with no overshoot. The green check (locked) appears for ext ref in auto, and also if I pick ext ref manually, so I suspect the check is amplitude driven... I have tried all the combinations of auto, tcxo, ext ref, connecting the ref, disconnecting the ref. Cannot find the combination that reliably stops the warbling. I can select tcxo with no ref connected, and once in awhile it clears, so I reconnect the ext ref, pick auto, and the warble comes back. Then I go back to the tcxo with no ref, and still the warble is there. The green check seems to always come on, and it will sometimes go into search, and come back with the check. What causes the warbling audio with the external ref hooked up?