[linrad] Challenges!!

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

Hi All,

Any interference that is not random can in principle be
modelled and subtracted. In real life it might be too 
difficult, but I guess there are man-made interferences 
that could be significantly reduced. Improvements are
also possible with random interference in some cases.

I think the interference fighting in Linrad can be 
significantly improved, but I do not want to work on
artificial signals where I try to simulate various forms
of QRM - mistakes are easily done so I look for real life
recordings of signals that are at the detection limit or
slightly below. 

Is there really nobody reading this who has problems in 
copying "the other station" occasionally? I have asked 
before, but still I have no recordings to work with.

Currently I am only interested in the traditional modes
CW, SSB, AM or NBFM. Here are a few examples:

1) SSB in white noise but with inadequate S/N. Rather than using
  a rectangular filter Linrad could use a filter that is shaped
  as the power spectrum of the signal.

2) Interference from TV transmitters on 50 MHz.

3) Lightening crashes on (low?) HF bands.

4) Splatter from local amateurs.

On Nov 05 I will leave for one month spending my time in
a more pleasent climate than what Sweden can offer this time
of the year. I will have plenty of time to work on any 
challenges you might give me.

The Tx side of Linrad is now producing 10mW on 144 MHz, but
I can not work on it when away from home because the next step
will be to arrange for the Rx/Tx switching for QSK in CW and
SSB. It is possible to listen while talking, one can "cut holes"
in the transmitted signal occasionally to generate perhaps 1% of
silence without affecting intelligibility. Will allow monitoring
of what happens in a pileup etc.

The next version, Linrad-02.40 will work under Windows Vista, 
but only with 16 bit audio. Please report all bugs you have 
noted in 02-39, I will upload 02-40 before leaving.

73

Leif / SM5BSZ


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