[Elecraft] K2 + SignalLink: Setting gains for digital modes

[Don Wilhelm]

Yes, the K2 transmit gain can change with the various bands.  There is 
some level of TX RF gain compensation in the K2 circuits, but it is not 
perfect.

Because of the way the K2 controls power, setting the power first and 
then bringing up the audio to produce that power output is a bit 
"iffy".  Adjusting the audio for no ALC indication as I stated earlier 
and then adjusting the power knob will always work.

Explanation -- The K2 tries to adjust the power output to produce the 
requested power in all cases.  If the audio input is too low, the K2 
measures the RF power output, then compares it to the requested power - 
the MCU will increase the power in an attempt to bring up the output 
power - your audio will still be low at that point, the K2 will increase 
the drive, and then when you subsequently increase the audio level, the 
power will overshoot the requested power, and then has to do the process 
over again to bring the power down.  The result is that there are often 
complaints about "power creep" when using digital modes.

For best results, adjust the audio level first for full audio but no 
ALC, then adjust the power knob.

73,
Don W3FPR


On 4/14/2013 3:23 PM, Bill Coleman wrote:
> On Apr 14, 2013, at 12:25 PM, Chris Kimball <mail at cvkimball.com> wrote:
>
>> I operate digital modes with the K2/KPA with a SignalLink computer interface.
>> The SignalLink drives the microphone input to the K2.  The K2 has
>> compression turned off (1:1) and a mike gain of 3.  The SignalLink computer
>> interface is at 100% gains on both sides and the SignalLink has the default
>> internal gain jumpers.
>>
>> I get occasional comments that I'm splattering, a very serious concern.
>> Unfortunately I lack instrumentation to study the problem.
> You have to adjust the gain as you change bands. Unfortunately the K2 gain profile varies wildly from band to band. Either adjust until you just barely get any ALC indication, or adjust until you just barely get the requested power out.
>
>>   How should I set the audio (SignalLink) drive gain and the RF (K2 Power)
>> drive? My normal operation is not smoke-producing, so this is not a
>> duty-cycle question.
> Set the K2 power level at whatever power you desire. Then increase the audio level until you just barely make that power level. You should be pretty close to just barely having ALC action.
>
> When you change bands, do it again.
>