On 8/5/2017 11:14 AM, Wes Stewart wrote:
But IMHO, you need to put a 30 dB attenuator on the input of the
internal sound card; it is way too sensitive. I'm having to run the
Windows gain at less than 5% and Line In at 10 or less.
Actually, you need to adjust the options in the Windows *.inf file
used for the PCM-series CODEC (or use the codec that identifies as
line level). Windows is turning on a 20 dB preamp in the CODEC.
I suspect if one sets the Windows Sound Options (Control Panel) to
display dB rather than percentage, the minimum level will be some-
thing like 16 to 20 dB! That indicated the fixed 20 dB "mic preamp"
is engaged.
73,
... Joe, W4TV
On 8/5/2017 11:14 AM, Wes Stewart wrote:
Wayne,
There are no beat notes. These frequencies, at least from the FT8
program in Tune mode are single frequency. Based upon output RF
spectrum measurements*, with for example 1010 Hz input and 4-5 bars of
ALC, I see spurious or intermodulation sidebands, down -65 dBc. If I
change nothing else but adjust the tone frequency to 1000 Hz the
spectrum is the same but the ALC bars are cyclic, going from none to
4-5, at about the 2 HZ rate Brian reported earlier. (Slow ALC in
action?) That's the good news.
If I set the tone to 1500 Hz, the FT8 mid-band target, I'm presented
with the cyclic ALC and some ~193 Hz, -50 dBc sidebands.
I have tried this with both the K3S internal sound card and via Line
In/Out into my laptop sound card. The results are more-or-less the
same. But IMHO, you need to put a 30 dB attenuator on the input of the
internal sound card; it is way too sensitive. I'm having to run the
Windows gain at less than 5% and Line In at 10 or less.
I would suggest that you do some measurements with a low-distortion sine
wave audio source run into the radio to eliminate the possibility that
this junk is a result of all of the digitally generated tones.
If this (what I will call a) problem continues to exist then I think a
fix is in order. Expecting users to select particular frequencies to
use to set gain levels isn't an acceptable workaround.
Regards,
Wes N7WS
* My "spectrum analyzer" is my SDR-IQ which I have used to measure TX
IMD on both my K3 and K3S. Your IMD
measurements on my K3S concurred with mine within 1 dB or less.
On 8/4/2017 4:45 PM, Wayne Burdick wrote:
Is it possible that a beat note between tones (and their harmonics) is
what’s modulating the ALC reading? If so, moving the tone slightly off
the standard pitch may be an acceptable workaround.
Wayne
N6KR
On Aug 4, 2017, at 1:42 PM, Wes Stewart<wes_n...@triconet.org> wrote:
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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