[Skimmertalk] CW Skimmer Server CPU overload caused by transmitting nearby (too many decoders)

[Bob Wilson, N6TV]

Can you please post the attachments somewhere?  The Skimmertalk reflector
deletes them.

However, it's usually impossible to keep a transmitter and a wideband
skimmer going at the same time at the same QTH without running into
problems like this.  I'm not sure what type of transmitter you're using,
but some transmitters are much cleaner than others.  Transmitting bandpass
filters may help a little, but maybe not enough.

Intermod from nearby non-linear devices (rain gutters, TV preamps etc.) can
cause hundreds of spurious signals to appear inside the Skimmer passbands
when you're transmitting, producing a huge number of decoders and CPU
overload.  The skimmer itself may be suffering from front-end overload.

According to this site, your z400 workstation has a Passmark rating about
40% slower than the one I'm using.

https://www.cpubenchmark.net/cpu.php?cpu=Intel+Xeon+W3565+%40+3.20GHz&id=1270


But it should be fast enough if you're not running RttySkimmer Server.

There's really no adjustment for this.  Automatically switching your SDR to
a dummy load while transmitting might be the best solution, but if you
prefer QSK like I do, you're out of luck.

I just terminate all skimmers at my QTH when I need to transmit.

Try transmitting into a dummy load.  Same problem?  Station leakage through
coaxes may be to blame.

73,
Bob, N6TV


On Fri, Jun 28, 2019 at 12:38 PM Andy KU7T <ku7t at ku7t.org> wrote:

> Hi,
>
> I can take down my skimmer server when transmitting on another antenna.
> This does not seem to be an HF issue, but CPU issue. When this happened, I
> can see that the CW skimmer tells me it has 19,000 decoders and the CPU was
> overloaded.  See attachment.
>
>
> The computer is running 2x8x192kHz for CW (thats 2 CW skimmer servers),
> 1x8x192kHz for FT8 (thats 8 instances of WSJT-x) and RBN aggregator.  I
> know that is a lot. On a quiet day, my CPU is between 60 and 70%.
>
>
> I can cause this failure while running 50 W FT8 on 20m into an antenna 200
> ft away.  I know I could disable the skimmer antenna with the PTT line but
> am wondering if this can be prevented by adjusting other parameters.  This
> is a dedicated computer (Z400 Workstation) that I do not need for anything
> else, so if it uses up to 80 or 90 % CPU there are no issues.
>
>
> Can CW Skimmer be told to not go higher than a certain CPU load or number
> of decoders? Or WSJT-X?
>
> Are there any other settings that could be changed, number of threads,
> etc.?
>
>
> See attachments.
>
>
> Thanks and 73
>
> Andy
>
> KU7T
>
>
>
>
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