[Elecraft] K3: Odd ALC behavior

[Dave Cole]

Please post resultd from WSJT-X, as that is what I am using.  I have 
noted that tune, vs. actual outputs act differently...  THANK YOU!

73s and thanks,
Dave
NK7Z
http://www.nk7z.net

On 08/04/2017 10:58 AM, 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
> 
> On 8/3/2017 13:25, Dave Cole wrote:
>> Hi,
>>
>> I have an issue in  regards to obtaining 4 bars, and getting the 5th 
>> bar of ALC to fluctuate while transmitting JT65.
>>
>> I have plenty of audio, and can drive the ALC to 6 or more bars if I 
>> turn things up.  However, as I get to 4 bars with the 5th flashing a 
>> bit, the ALC starts to fluctuate between nothing and 4 or 5 bars...
>>
>> That is to say, the ALC just goes to zero, no visible ALC, and then 
>> teh ALC returns to 4 or 5 bars.  This happens across a one or two 
>> second time span.
>>
>> The ALC is at zero more than it is above zero most of the time. If I 
>> run it to five bars, with the fifth fluctuating, all is well, there 
>> seems to be some sort of threshold at the 5th bar of ALC...
>>
>> I have tried a number of things to try and triage this...  For instance:
>>
>> 1.  Running in "Transmit Test" mode to eliminate RF feedback.
>> 2.  Upping the audio level feeding the K3.
>> 3.  Reducing the audio level feeding the K3.
>> 4.  Upping the line in on the K3 setup.
>> 5.  Reducing the Line in on the K3 setup.
>> 6.  Adjustment of the WSJT-X output level control, under conditions 2 
>> through 5 above.
>>
>> In all cases the above described behavior of the ALC dropping to zero 
>> does not change in any way if I am at 5 or less bars.  That is to say, 
>> if I take the ALC level to 4 bars, it starts dropping to zero more 
>> than not...
>>
>> Does anyone have any suggestions as to what this might be?
>>
>> A a bit of history-- the computer and sound card were used on an Icom 
>> 756 ProIII, and there was never an issue like this...  The ALC was 
>> adjustable from zero to too much on the Icom, with no dropouts...
>>
> 
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