[Elecraft] SSB Power Creep

[Jack Berry via Elecraft]

I notice on MARS frequencies (slightly outside ham bands) that my power output starts out low and builds to full output over 10-20 seconds of transmit. The symptom is easily observed during an MT63 transmission and receiving stations comment that my signal starts out light and builds to a strong signal as the transmission progresses.
I have run the calibration routine several times into a dummy load and all seems to go well but the problem persists.
I see the same symptom in some ham bands but to a lesser extent, perhaps starting at half power and coming up to full power in a 10 seconds.

Has anyone else experienced this or have ideas about a fix?

 
God Bless & 73!
Jack - WE5ST