[Elecraft] K2/100 down power on 20M

[jerry]

OK,

    With a dummy load - actually a 500W Bird 30dB attenuator - the 
displayed power out came up to 78W.
I tried adjusting the bandpass filter - it was already spot on.  They 
use one filter for 40M and 30M,
and you go back & forth between the two.  It was already perfectly 
peaked & tweaked.

    What about the KPA100?  I turned the power down to 10W, taking it out 
of the circuit.
20M - 9.6W
30M - 10.23W

   With power set to 40W:
20M - 41.7W
30M - 42.5W

   With power set to 60W:
20M - 56.8W
30M - 62.5W

   With power set to 80W:
20M - 71W
30M - 77.6W

   With power set to 100W:
20M - 78.6W
30M - 91.7W

  With power set to 110W:
20M - 78.6W
30M - 98.5W

   I suspect that the problem is in the KPA-100.  Maybe a wrong value in 
the LPF?
Power out with control set fully clockwise, into the dummy load, 
measured by the Telepost:
80M - 120W
40M - 104W
30M - 97.7W
20M - 79.4W
17M - 98.3W
15M - 88W
10M - 74.5W

   Interesting, according to the KPA100 manual, 20M and 17M share an LPF. 
  If it was out of whack, I'd expect 17M to be MORE
effected than 20.

                    - Jerry, KF6VB






On 2024-03-16 09:10, Joe Subich, W4TV wrote:
>> But before that, I should redo the test with a dummy load.
> Yes.
> 
>> And it's not just gain decreasing with rising frequency, because it 
>> does 92W on 15M, 76W on 10M.
> First suspicion ... check the alignment of your bandpass filters.
> 
> 73,
> 
>    ... Joe, W4TV
> 
> 
> On 3/16/2024 11:56 AM, jerry wrote:
>> Hello,
>> 
>>     I've been doing a bit of operation with my K2 lately.  It really 
>> is a joy on CW, and it fits perfectly under my big computer
>> monitors.  But I have noticed....   On 40M, it does 101W out.  But on 
>> 20, only 63W.  This is measured with a Telepost LP-100A vector
>> wattmeter.  The SWR is 1.4 to 1.
>> 
>>    And it's not just gain decreasing with rising frequency, because it 
>> does 92W on 15M, 76W on 10M.
>> 
>>    Guess it's time to get out the schematics...  But before that, I 
>> should redo the test with a dummy load.
>> 
>>                   - Jerry, KF6VB
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
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