[Elecraft] K2 input level in data modes

[John, KI6WX]

Julian;
Have you installed the PSK31 mod to the KSB2.  The original ALC circuit
could not handle PSK31, so I generated a set of changes to increase the
decay time constant.  The effect you are seeing is the normal gain increase
that occurs when bipolar transistors warm-up.

The mod is posted on the Elecraft sight and is now standard for the KSB2.

-John
 KI6WX


> 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
>
>
>
>
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