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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