[linrad] Re: MAP65 and Linrad Network

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

Hello Joe,

> I've noticed one interesting thing while playing with MAP65 
> today.  Even though I have assigned its "recvpkt" thread an 
> "ABOVE_NORMAL" priority, I can cause it to drop UDP packets 
> by having Windows do various things.  (For example, starting 
> up the Windows Task Manager.)  The number of lost packets is 
> normally small (say 1-5), and since there are some 33000 
> packets in a one-minute data block, the losses are probably 
> negligible.  I will watch it, and probably put in a warning 
> flag or something.
Yes, but as long as you fill zeroes in the corresponding
locations so there is no time shift, small drop-outs will not
have any effect on S/N at all under normal circumstances.

Only if you have a VERY strong signal present, a drop-out
will create a pair of keying clicks when the signal disappears
and when it comes back again. On the Windows computer this is 
totally impossible if the input comes from Linrad with the 
noise blanker in 16 bit format. There can not be any strong 
signals!!
 
> If anyone is interested in testing an early version of 
> MAP65, please let me know.  I can probably make one 
> available fairly soon.  You will need two computers with a 
> network connection between them.  The MAP65 computer should 
> have 1 GB or more of memory.
Hmmm, on a good computer you could run Linrad under Windows 
on the same computer that you use for MAP65:-)

Currently I have no antenna so I can not play with the software.
Perhaps you could press "S" in Linrad to record the raw data for
perhaps 20 minutes and then upload the file on the Internet?

If you use the Delta 44 soundcards in 32 bit mode, the file
will contain 18 bits per sample and if you select 16 bits, the
file will (of course) contain 16 bits per sample.

The file will contain the calibration functions of your system
to allow an identical processing with what you can do while 
recording. 

96000*4*2*60*20=922 megabytes for 20 minutes of 16 bit data which
could perhaps be compressed with bzip2 since 50% of the data is 
0 or -1 while there is no strong signal present and 8 bits would 
have been sufficient (I do not know whether bzip2 actually can
utilize this).

In 18 bit mode the file would be 1037 megabytes that can not be 
compressed.

73

Leif / SM5BSZ




> 
> 	-- 73, Joe, K1JT
> 
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