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[aprssig] Building a new digi (RX performance?)

Robert Bruninga bruninga at usna.edu
Wed Apr 1 22:49:13 UTC 2009


> The T2-301 will actually do 9 or 10 watts 
> if you crank it up all the way.  Assuming 
> you're not using it on commercial frequencies, 

I'm sure the radio specs are very good on receive sensitivity
too, but what really matters is how well the combination of
radio and TNC can decode received packets.  We have done some
testing over the years and have seen as high as 20 dB or more
decoding problems (usually due to other people's transmitted
signals formed by just plug-n-playing a TNC to a xmtr and not
adjusting levels..

If you listen to 144.39 in the USA, I'd say 80% of the
transmitted signals are an embarassement.

I use the TH-D7 as a bench mark, since so many of them are out
there, and they are an all-in one factory integrated receiver
and decoding system.  I have found that they can decode signals
down to one bar on the LCD display.  We measured that minimum
signal as -117 dBm 

I wonder if you have done any testing of your combination as to
on-air receive and packet decode performance?

Although decode performance on a tracker isnt usually that
important, it is when it is placed in digipeater service.  ...
Just curious.

Thanks
Bob, WB4APR




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