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RE: [Linrad] Re: First real EME tests with MAP65-IQ
- Subject: RE: [Linrad] Re: First real EME tests with MAP65-IQ
- From: "Gabriel - EA6VQ" <vhfdx.net; ea6vq.1@xxxxxxxxxxxxxxxx>
- Date: Mon, 30 Mar 2009 15:50:06 -0000
Many thanks for the details. I will try what you suggest next time I can go
to the radio QTH and I will let you know the results.
73. Gabriel - EA6VQ
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> -----Mensaje original-----
> De: linrad@xxxxxxxxxxxxxxxx [mailto:linrad@xxxxxxxxxxxxxxxx]En nombre de
> Leif Asbrink
> Enviado el: sábado, 28 de marzo de 2009 21:46
> Para: linrad@xxxxxxxxxxxxxxxx
> Asunto: [Linrad] Re: First real EME tests with MAP65-IQ
> Hi Gabriel,
> > First, the signal levels reported for the selected frequency
> > are between 3 and 5 dB weaker than with WSJT6. I was running
> > MAP65 and WSJT6 in parallel and I could see that difference
> > for all signals. When a signal is, for instance, -22 dB in
> > WSJT6, the same signal is between -25 and -27 dB in MAP65.
> > When the band is noisy the difference is smaller (might be
> > 1 dB weaker in MAP65), possibly because of the excellent
> > noise blanker of Linrad.
> Try to set OL_RCF to 5 instaed of 6. (You may edit par_sdr14)
> That will increase the signal level by 6 dB. Set the first FFT
> amplitude to 1000 (default in Linrad) and adjust the gain of the
> analog hardware to place the noise floor in the main spectrum
> at 20 dB. You may use the gain setting in the frequency control
> Then verify that the noise floor drops by at least 15 dB when you
> switch off the DC power to your 144 MHz preamp.
> The green bar in the high resolution graph should now be about
> 6 dB above the thin red line. I think that is a bug in Linrad
> (I did not verify how the noise computation was normalized in
> a single channel system)
> With these changes you should see the same S/N reports in
> MAP65-IQ and in WSJT6 when both systems are run without
> a noise blanker.
> > Finally, near the moonset the band was really noisy
> > and I noticed that some signals that were clearly
> > visible in Linrad's waterfall were not visible at all
> > in MAP65's waterfall, and it did not decode them either.
> > Anyway this was only in very noisy conditions, due
> > to power lines.
> Once you have corrected the signal levels and verified
> that preamp on/off affects the noise floor as expected
> while your antenna points towards quiet sky, please make
> a wideband recording with Linrad next time you have really
> bad power line noise.
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