[Moon-net] Experimental Digital Modes

[Leif Asbrink]

Hi Lance,

> 1) Many locations outside Region 2 are subject to intense interference
> from "channel 1" TV transmitters, which tend to create spurious
> "birdies" spaced about 50 Hz apart.  The fact that JT4A could fit
> between such "birdies" could afford great new possibilities for weak
> signal work at such locations.

This kind of QRM could be removed by an SDR. Linrad already has a 
function that might do the work, but for this special case it could
probably be greatly improved sinc birdies are currently removed 
one by one without using the phase relation between them.

I have asked for "challenges", i.e. recordings of signals that
are difficult or impossible to copy due to various kinds of
interference in order to have test files to try different
interference rejection routines on. Unfortunately I did not
get any response. Seems like nobody ever has any difficulty
to copy a station except for too low S/N in a white noise
background.

Now you have mentioned an obvious challenge. I would be very 
interested in a recording - and more bandwidth is better.
Equidistant birdies correspond to a pulse train and maybe
the TV QRM is better to fight in the time domain. More 
bandwidth then means better time resolution.

Is there anyone who could make a wideband recording of
a typical 6m TV-QRM situation?

Other situations with marginal or impossible copy are also
of interest. Two things that can be improved are but where I
have no test data is:

1) Marginal SSB in white noise. (Adaptive filter can be added)

2) Lightening crashes, presumably on HF bands. (A narrowband
noise blanker)

I need test files before Nov 05, then I will leave home
for one month having my laptop and plenty of time to 
work on interesting SDR problems at a place where the
climat is much better than in Sweden this time of the 
year:-)

73

Leif  /  SM5BSZ