[linrad] Re: MAP65 and Linrad Network

[Joe Taylor <Princeton.EDU; joe@xxxxxxxxxxxxxxxx>]

Hi Leif,

Thanks for your message.

> > ... 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.

Yes, this is exactly what I have done.

> > 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:-)

Yes, it should be possible to run everything on a single 
fast computer with plenty of memory.  I have not yet 
established that the necessary CPU-sharing during 
time-critical parts of each program is handled adequately 
for this to work without glitches.  Neither Linrad nor 
Windows is a very good real-time O/S, and one must work 
around their limitations in this area.

Moreover, one will almost certainly want separate screens 
for Linrad and MAP65 -- both of which generally use most or 
all of a normal-size screen.  I do not presently have a 
"two-headed" computer, so I am doing initial testing of 
Linrad/MAP65 with a two-computer setup.

> 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?

For testing MAP65 when real signals are not available, and 
anyway so that I can get 100% repeatable results, I solved 
this problem in a slightly different way.  I saved some data 
by using the Linrad "S" command during the ARRL EME contest 
last November.  With a slightly modified Linrad I converted 
the data to 16-bit TIMF2 format, and wrote it to a file.  A 
simple program that I call "plrs" (for "pseudo-Linrad send") 
can read this file and multicast it in the same way that 
Linrad would do, so that MAP65 can receive it.  The data 
file, 11 minutes of original data, amounts to 507 MB.  After 
compression with bzip2 it is 228 MB.  I will make the data 
file available soon, together with plrs and MAP65, to anyone 
who wants to participate in testing MAP65.

	-- Joe, K1JT

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