[linrad] Re: Linrad-02.39

["Joe Barger" <aero.org; barger@xxxxxxxxxxxxxxxx>]

Hi Leif,

Thanks very much for the new calibration and automatic spur removal 
functions.  Fantastic!

> There is now a new page about calibration in Linrad:
> http://www.sm5bsz.com/linuxdsp/flat/ampcal.htm

The links to the data files (blinkerinitx.xxx) are broken (but I found them 
anyway :-)).
One small issue, in windows, adfile is selected instead of adfile.txt 
(assuming both are present).

> I have not had much feed-back on whether the changes in users.c
> and users_tr.c have caused problems or if there have been other

I have not tried the transmit function, but have noticed no problems in 
other functions so far.

I have Linrad and MAP65 running on the same computer under windows.  I am 
using windows remote connect on a second comuter to display and control 
MAP65 as it runs on the first computer.  Amazing combination.  I can now 
copy signals that were buried under local noise before.  Now to get the 
transmit side working and make some EME contacts!

> I am still looking for "interesting" interference situations.
> You may have seen "Reserved for blanker" in the baseband graph.
> This is a routine that should help against lightening crashes
> on HF bands and perhaps in other situations where interference
> pulses are not local and therefore suffer from multi-path
> propagation.
>
> Is there NOBODY on this list who ever tries to copy a signal but
> has big difficulties due to interference of some kind (or in SSB
> has a too low S/N) ???
> I am very interested in recordings of marginal "copy" or "no copy"
> in CW or SSB. Maybe DSP could improve :-)

I'll try and find some files for you to work on.  I'm pretty sure various 
low banders have samples out on the web of signals fading in and out of the 
noise (complete with static crashes, powerline noise, electric fences, 
plasma TV buzz, ethernet birdies, etc.).  I'll make a recording of my 144 
MHz environment that will be a real challenge!

Another one of my interests is low band (160/80 meters) where my noise level 
is very high.  I have been thinking about installing a 4 square receive 
antenna system similar to the DX Engineering system ( 
http://www.dxengineering.com/ ) or perhaps the 2 antenna version with the 
NCC-1 noise cancelling unit.  It seems to me that the primary functions of 
these units (controlling the position of the main lobe of the 4 square 
and/or noise cancelling) would be better accomplished in DSP (certainly 
cheaper).  I was thinking about using four 160/80 meter softrocks (one for 
each antenna with common sampling clock) and feeding the I/Q output of each 
softrock into one channel of a D44 sampling at 96KHz.  That (I think) would 
result in ~48 KHz sampled bandwidth (which may not be wide enough for very 
effective noise blanking) and the softrocks probably aren't the best 
frontends, but it would be a very interesting (cheap) experiment.  Are these 
functions (antenna beam forming and noise cancelling) something Linrad could 
accommodate?  :-)

Thanks again

73

joe n6kk





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