[Elecraft] K2 input level in data modes

[Julian (G4ILO)]

I'm wondering whether anyone who uses their K2 for data modes has noticed 
the following behaviour, and even better, can offer an explanation.

I haven't changed the audio level output using the computer mixer, nor the 
K2 menu SSB settings, for a very long time, and everything was adjusted to 
give 5W output with 1 bar of ALC showing. Recently I turned on, listened 
around for a while and then called a station, and noticed the output was 
very low. But after checking everything and doing a Tune, all seemed OK.

Today the same thing happened, so I decided to investigate further. I hit 
the software Tune button to generate an idling PSK31 signal, and initially 
no bars of output RF were showing, then the power output climbed over a 
period of 10 secods or so to the usual steady 5 watt level. After that, I 
immediately get 5 watts output whenever I go to transmit. I can't think 
that it is the gain increasing as the K2 warms up as the time is too short, 
and the output remains correct even if there is a long interval between 
transmit times. If I turn off the K2 for 10 minutes or so and then turn on 
again the level has dropped again, although it only took a couple of 
seconds to get back up to 5 watts this time.

Audio frequency is always the same, so it's nothing to do with being on the 
wrong part of the SSB filter passband. RTTY mode is selected, to the 
compressor is automatically disabled.

I can't think what is causing this unless the firmware has a feature, 
unknown to me, of detecting a low audio input and automatically increasing 
the gain until the power hits the level selected.

73,
--
Julian, G4ILO. (RSGB, ARRL, G-QRP, K2 #392)
G4ILO's Shack: http://www.qsl.net/g4ilo