[Elecraft] K3: Odd ALC behavior

[Wes Stewart]

Good find Brian!!! I see it too in FT8.

This probably explains the great variability in results reported. Some of us 
have a problem, others say, Huh, what the heck are you talking about?

Wes, N7WS


On 8/4/2017 11:33 AM, Brian Hunt wrote:
> Here's some followup:
> FLDIGI shows the "pumping" affect with carrier tones of 500, 1000, 1500, and 
> 2000 Hz.
> WSJT-X 1.8 shows the "pumping" affect with carrier tones of 1000, 1500 and 
> 2000 Hz (couldn't select 500 Hz).
>
> The affect is very narrow with frequency.  10 Hz either way and the output and 
> ALC display and MON output is rock solid.  Changing the K3 filter center 
> frequency has no effect on the above.
>
> 73,
> Brian, K0DTJ
>
> On 8/4/2017 10:58, Brian Hunt wrote:
>> I spent some quality time with my K3, FLDIGI and an oscilloscope today.  I 
>> had the same problem as described.  Looking at my USB soundcard output to the 
>> K3, the amplitude of the audio from FLDIGI in TUNE mode was rock solid. 
>> Looking at the MON output from the K3, the level oscillated in time with the 
>> ALC "pumping" at about 2.4 Hz (timed with a stop watch).  At the same time 
>> the K3 power output into a dummy load was rock solid at a selected 10 watts.
>>
>> Then I changed the carrier frequency in FLDIGI slightly off 1500 Hz and the 
>> "pumping" went away!  At 1515 Hz I could easily set the ALC to the desired 4 
>> bars solid, 5th flickering.  Then I remembered (and verified) that the 
>> default filter center in DATA A mode is 1500 Hz. I changed the filter center 
>> frequency to 1450 Hz and moved the FLDIGI frequency around but couldn't 
>> reproduce the "pumping".
>>
>> I plan to repeat the same tests with WSJT-X 1.8 but wanted to get this out to 
>> the group.
>>
>> 73,
>> Brian, K0DTJ
>>
>
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