Re: parameters - ssb receiver and single polarization

[n1ki <arrl.net; n1ki@xxxxxxxxxxxxxxxx>]

Thanks Leif,  I have been receiving overrun_error on the screen in
both weak signal and calibration screens.  What can I do to correct
this?   73, Phil

On Dec 16, 7:33 pm, Leif Asbrink <l...@xxxxxxxxxx> wrote:
> Hi Phil,
>
> > Hello everyone.  I have Linrad running under windows with a Kenwood
> > TS-2000, a 4X12 horizontal array, and a 2.8 GHz AMD Athlon with a
> > SoundBlaster card.  I have the screen set up to my liking, and I have
> > been studying the fft process and have read many of the web pages on
> > Linrad and am beginning to learn my way around.  I plan to perform the
> > noise blanker calibration in the next week.  My main interest is 2
> > meter and 70 cm EME.  Which parameters should I concentrate on to
> > optimize weak signal detection?  My noise background on 2 meters is
> > reasonably quiet, but I have a local pulsing interference on 70 cm.
>
> I do not know the TS2000 well. Maybe it has a noise blanker
> that operates in a wide bandwidth. If it has, it could be better
> to allow it to take care of pulse interference. On HF bands it
> may be different because wideband blankers that are built into
> transceivers do not work well if there are strong signals anywhere
> in the wide bandwidth of the blanker. Then the Linrad blanker
> might do much better within the bandwidth it has. Surely more
> bandwidth improves greatly, so set the bandwidth as wide as possible.
>
> For the blanker to work, and for other reasons as well, you should
> disable the AGC of the TS2000. Set the RF volume for the signal
> to not saturate (or engage the AGC) for the strongest signals
> or noise spikes you normally have. The lower signal level you
> run at, the better dynamic range you will have, but do not set
> the level too low because at some point the noise figure of
> your system will start to degrade. 60Hz and its overtones might
> also become a problem.
>
> In other words, make sure that the TS2000 works in a linear mode
> for all signals that you expect while also making sure that the
> system NF is OK. (disconnecting the DC power to your antenna
> mounted preamp should lower the noise floor by about 15 dB.)
>
> Set the BFO pitch, passband tuning or whatever they call it
> on a TS2000 for a somewhat higher pitch than normal. 60Hz
> overtones might reach up to 400Hz or so and it would be
> a good idea to have them outside the frequency range of
> interest. Make sure you do not loose bandwidth, more bandwidth
> is always better.
>
> After you have done the calibration you must NOT change
> the bandwidth tuning or BFO pitch. Even small changes
> will destroy the wider and flatter noise floor that
> the calibrated system benefits from.
>
> With a calibrated system you can run the waterfall slower
> and increase the waterfall gain to see signals deeper down
> below the noise floor.
>
> Do whatever seems reasonable and use Linrad a little
> so you become somewhat more familiar to it. Then press
> the 'S' key some time when you have a signal you can not
> quite copy. Record it for one minute (or close to.)
> Then press 'S' to stop recording,'G' to save a gif file
> with what you have on the screen. Finally exit and save
> all the parameter files par_* somewhere. Pack the parameter
> files in an archive file and make everything available
> to me:-)
>
> 73
>
> Leif / SM5BSZ

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