[Spooks] Re: Cuban unid digital signal

[Hugh Stegman]

KD7JYK wrote:

  > That sounds kind of dumb, are you sure that's what Hams are doing?

That's exactly what they are doing. They are on nominally 14233, though 
I get the best tuning on 14232.98.  When I first heard this activity 
they were occasionally using DIGTRX in Ham-DRM mode.  Now they are using 
a different DRM program that I can't get to work on this machine without 
turning off functions I need for other programs.  DIGTRX works with 
this, as verified by one or two successful file decodes here, but they 
claim the decode is better if you use the same program they used to 
encode it.

They send the file once, and then the receiving station clicks a button 
and the software asks for fills of missed packets.  The programs have 
the capability to send files multiple times, but this results in a very 
long transfer time and they don't do it this way.

DRM in general is not the best mode for amateur gear and regulations. 
The peak/average ratio is such that the US legal 1500 watts PEP output 
results in something like 150 watts average when sent in USB.  Stations 
that bend the meter on USB voice go into the noise on DRM.  In voice 
broadcasting, this would just cause the signal to cut in and out, but 
for file transfers you really need big beams pointed at one another and 
high power.  I just don't think it's an efficient amateur mode.

-hugh