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

[N4ZR]

I ran a QS1R with Skimsrv at my old QTH, running 1400 watts input.  
Through experimentation I discovered that with my Clifton active whip 
about 300 feet from my transmit antennas, I could use PTT to *open* the 
antenna lead at the QS1R's input and totally quiet it down.  I 
experimented with shorting the input first, but it did not work nearly 
as well.

I've observed that both the QS1R and my new RP-16 spawn decoders on 
multiple bands in response to thunderstorms in the area.  Generally 
these expire very quickly.  I get somewhat the same effect if I connect 
and disconnect antennas from the SDRs while they are running.

73, Pete N4ZR
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On 6/28/2019 4:17 PM, Bob Wilson, N6TV wrote:
> 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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