[K3S] Loss of audio quality

[Bill Frantz]

I am using a K3 that has been upgraded to include the KIO3B
three board set with USB audio to the computer. For several
years, it has been working well with my MacBook Pro.

Recently, my decoding of FT8/FT4 signals has become much worse.
I see a large number of signals on the wsjt-x waterfall, but get
very few decodes. I don't think this is a time of day problem as
when I do get decodes the displayed times are on the order of
0.1 or 0.2 seconds. (I have played a lot to be sure NTP is
working correctly.) I have also adjusted the RF gain to between
30 and 70 on the wsjt-x signal level display. Changing between
30 and 70 doesn't change the number of decodes.

I ran some experiments today to try to locate the problem.

(1) Since there was a RTTY contest in progress, I compared the
decodes I was getting on the computer with cocoaModem with the
ones I was getting from the K3's internal decoder. The K3's were
significantly better.

(2) I played the FT8 subband through the radio's loud speaker
and used the internal microphone on the computer to listen to
the signals. I got a lot more decodes (and the times were
consistant with a correct time setting on the computer).

I am starting to conclude that there may be a problem with the
USB audio. I will try to hook up the external sound card I use
with my KX3 tonight and see if it works better than the KIO3B.

Has anyone seen these symptoms? Do you have any fixes?

73 Bill AE6JV

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[Jim Brown-10]

On 9/27/2020 3:09 PM, Bill Frantz wrote:
> Has anyone seen these symptoms? Do you have any fixes?

Bill,

One thing I've seen with Windoze laptops is the OS switching the audio
input to the decoder to the computer's built-in mic. You'll get decodes,
but not nearly as many as usual. :)  The quick test for it is to bang on
the computer and see if you see audio level change.

73, Jim K9YC
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