[aprssig] A Closer Look at the WA8LMF TNC Test CD

Scott Miller scott at opentrac.org
Fri Jan 1 22:31:13 EST 2016

Thanks for the analysis!  If I remember right there's some CW ID in 
there, too.  My intent with the CD was to get something comparable to 
the old Bellcore tapes for DTMF.  A larger corpus with samples taken 
from different regions would be good to have.  Stephen stepped up and 
captured the LA traffic and I figure that area's got to be about as bad 
as any.

My timestamps for the files say 2007.  Might be interesting to take 
another look at the same region and see how thing have changed over the 
years.  My guess is that we'll see more D700s, D710s, FTM-350s, and 
FTM-400s with more consistent deviation, but if I know anything about 
hams it's that they never throw anything away and there's bound to be a 
lot of ancient stuff on the air too.  It'd be nice if more hams had the 
ability to measure deviation directly - and the inclination to do 
something about their settings.

I keep thinking I'm going to take the physical CDs off the online store 
(and we stopped printing nice labels for them years ago) but people keep 
ordering them.  I'm kind of surprised that so many people both have an 
interest and don't want to burn it themselves.


On 1/1/2016 6:07 PM, John Langner WB2OSZ via aprssig wrote:
> How can we compare how well different TNCs decode less-than-ideal APRS
> signals?  The de facto standard of measurement is the number of real-world
> frames decoded from WA8LMF's TNC Test CD.
> Let's take a closer look at some of the frames on the TNC Test CD in hopes
> of gaining some insights into why some are easily decoded and others are
> more difficult.
> This document contains images of really ugly APRS radio signals that some
> will find disturbing.  Viewer discretion is advised.
> https://github.com/wb2osz/direwolf/blob/dev/doc/A-Closer-Look-at-the-WA8LMF-
> TNC-Test-CD.pdf
> There are a lot of ugly signals out there.   Many can be improved by
> decreasing the transmit volume.   Others are just plain weird and you have
> to wonder how they are being generated.
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