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1334Re: WANTED 8KHz OP4H OPERA TESTER'S (Mix ~1000Hz with 9 KHz ?)

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  • p.knol
    May 1, 2012
      Hello Graham,
      I think that must be it. Intermodulation...

      Now testing LOCALY with notebook PC and a Loop antenna at the LS output. The RX computer is connected to the PA3RDT Mini Whip antenna
      in the backyard.

      Some comments:
      1)Perhaps a idea to slow down the waterfall, zoom it at 9 KHz and/or let is scroll horyzontal ?

      I did degrease my TX signal level until the trace was 'just' visible in the OPERA spectrum. I run Spectrum Lab parallel at the RX PC, but there is the transmitted OPERA signal almost overloading-bright in the Spectrum Lab Spectogram.

      2)When I increase audio input till it reach about 10 / 11 o'clock at the VU indicator (33% ?) it is already overmodulated. I see intermodulation signals arise at 33% level. I did adjust input till signal was best visible in spectrum, then level indicator is most of the time in the yellow section at 9 o'clock with level -24dB. The VU meter indicator is very servous and often jumps from 9 o'clock to 11 o'clock. CPU use is 14% here at my ACER Extensa 5235 notebook.

      That's it for now. Results take some time :-)

      Peter, PA1SDB

      --- In O_P_E_R_A_@yahoogroups.com, "graham787" <g0nbd@...> wrote:
      > Ok , the waterfall shows only 8 to 11 Khz, But you say you are using a microphone ? I think you are seeing some inter modulation and possibly harmonics from the whistle .by default the waterfall is showing very low signal levels .. so these hf products may be quite low?
      > Good luck with the monitoring, if you know any local stations testing with 100% carrier, see if they will add the OP4H modulation , if they are not Op users normally !
      > Tnx -G.
      > --- In O_P_E_R_A_@yahoogroups.com, "p.knol" <cyberknol@> wrote:
      > >
      > > Hello Graham. Interesting. I'm a 8 KHz listener for one month or so:
      > > http://www.qsl.net/pa1sdb
      > > <mhtml:{66EE0916-36F0-490E-81AB-E0CD8BF2F936}mid://00000272/!x-usc:http:\
      > > //www.qsl.net/pa1sdb> Just wondering why the audio spectrum (~1000
      > > Khz ) becomes mixed with 9 Khz in the waterfall spectogram. Take a
      > > look here.... <--- <http://www.qsl.net/pa1sdb/OPERA_8Khz.jpg> Above
      > > you see a 9010 Hz carrier generated by Spectrum lab, and me whistle
      > > around "1500 Hertz. Both recorded via the mike input at the notebook and
      > > become visible in the waterfall. Totaly at top (2mm), I did hit the
      > > "PrtSc + Alt" buttons :-) Best 73's, Peter - PA1SDB
      > > http://www.qsl.net/pa1sdb
      > > <mhtml:{66EE0916-36F0-490E-81AB-E0CD8BF2F936}mid://00000272/!x-usc:http:\
      > > //www.qsl.net/pa1sdb>
      > >
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