[Elecraft} K3 power control in ssb

[G3TCT]

Others have already mentioned this as a problem and I have just tested my K3 #1198 driving an Acom 1000 amp into a dummy load with the following results.

Condx:-  3.7MHz, 25w drive to get 392w o/p on cw.  

I have TXG VCE set to -1.5dB, mic 15, cmp 24.

 

In lsb and then key down I adjust to just under 400W o/p. Then lsb gives 200-300w initially.  After speaking and then pausing a few times for a minute or so I get 400-600w out!!  The K3 system has turned up the gain – if I then go to rx and then key down I get an initial o/p of about 540w which then rapidly scales back to 400. Then speaking on lsb I'm back at the 200-300w o/p which gradually increases again. So there's a gain change going on which seems to be reset by a key down.

 

Hope this helps Elecraft or others in analysing the problem.

Graham

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[Ignacy]

I noticed that too. Not a big concern here as my linear is 2 x 3-500Z but would be a concern with high gain tubes.
Ignacy

Graham Kimbell (G3TCT) wrote

Others have already mentioned this as a problem and I have just tested my K3 #1198 driving an Acom 1000 amp into a dummy load with the following results.
Condx:-  3.7MHz, 25w drive to get 392w o/p on cw.  
I have TXG VCE set to -1.5dB, mic 15, cmp 24.

In lsb and then key down I adjust to just under 400W o/p. Then lsb gives 200-300w initially.  After speaking and then pausing a few times for a minute or so I get 400-600w out!!  The K3 system has turned up the gain - if I then go to rx and then key down I get an initial o/p of about 540w which then rapidly scales back to 400. Then speaking on lsb I'm back at the 200-300w o/p which gradually increases again. So there's a gain change going on which seems to be reset by a key down.

Hope this helps Elecraft or others in analysing the problem.
Graham
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[Laurent F6DEX]

Hello

Something similar (V 2.82 and previous).

K3 set to max power (12W here)
Change power to 6W (or any power but not max power)
First key down (CW SSB Tune) power = 9W (about)
Second key down power = 6W

In fact any change of power is not taken properly for the first key down.

I can repeat this behavior easily by setting up the power to maximum, keying down  and then reducing the power to any value... This is a problem with a linear amplifier.

73, Laurent