[Linrad] Re: Perseus with Linrad

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hi Corneliu,

> I guess that your calibration files for Perseus
> will be useful to all Perseus owners.
Yes:-)

> I have tested Perseus plus a downconverter 144/28 with a signal
> generator and a calibrated attenuator with 1 dB steps
> for MDS and have discovered that Linrad and Winrad main waterfalls are
> about 10 dB more sensitive than Perseus software.
There is not really any limit. You can set the bandwith extremely
narrow in Linrad and average over VERY long times so you can find
signals that are very much weaker if you wish. That is really the problem
with Linrad. Any setup I might suggest will be targeted to some
particular usage and your interest could be something else. That
is why I do not supply parameters for any particular hardware
but rather for specific usages.
http://www.sm5bsz.com/rf_library.htm
http://www.sm5bsz.com/linuxdsp/usage/examples.htm
There are many links here:
http://www.sm5bsz.com/linuxdsp/linroot.htm
Some of them give examples on various usages of Linrad.

> also noticed that even if in the Perseus main waterfall you could not
> see anymore the signal, in the extended window the signal was still
> about 10 db above noise floor.
This just depends on the parameters you have selected. Linrad allows
you th have it the other way around in case that is what you want.


> Also noticed that even if in Linrad baseband waterfall the  signal was
> still visible, you could not detect the signal audio output by ear...
YES:-)

> I have noticed also that the dumb noiseblanker is quite effective
> except in the condition when the signal is very close to the noise
> floor when also the signal gets attenuated by blanker
That is because you do not use the dumb blanker properly. (I think)

> I would appreciate if you could supply the Linrad optimized settings
> for Perseus week signal detection
There is no such thing. Your local QRM/QRN situation might make
it optimal to use a different calibration or different sizes
for transforms. What you mean by weak signal is also a personal
matter. Chasing weak EME signals is quite different from 
chasing weak SSB bursts in meteor scatter SSB. If you want to work
weak signals in a terrestrial contest I guess you would not want
the delay from antenna to loudspeaker to exceed 2 seconds or so.
(In EME, 10 seconds is fine.)

I have asked (many times) for recordings of situations where a signal 
is difficult to copy in order to use such examples here:
http://www.sm5bsz.com/rf_library.htm

There are many interesting aspects of interference fighting 
and signal detecting that I would like to demonstrate - but
I want to do it on real signals not just simulations of mine.

> Pls also advise if the a.m. findings are correct.
Something is wrong with your blanker observations. Otherwise
I think it is correct (but very limited.)

73

Leif / SM5BSZ


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