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[aprssig] Proper deviation levels

scott at opentrac.org scott at opentrac.org
Tue Nov 28 05:19:21 UTC 2006


> The ratio Stephen mentions only holds true if the radio conforms to 
> 6dB/octave. Consider both tx and rx in this regard (my old 

At the moment I'm just making sure everything's kosher on the TX side -
i.e., the relative levels of the tones are right as they exist on-air.
Proper deemphasis is a separate problem.

> rather than both tones being approximately equal, as presented to the 
> TNC. XR2211/2206 based TNC's don't take kindly to the high tone being 
> lower in level than the low tone.

Tell me about it.

At least I'm now able to directly verify that the preemphasis filter in my
T2 board for the DR-135T is working right.  The internal connection isn't
preemphasized, and I didn't want to make the TM-D700's mistake of
transmitting flat when everyone else is expecting 6 dB/octave.

Oh, and on an unrelated note, I've got support for the La Crosse WS-2300
series weather stations in the Tracker2 now.  Haven't been able to back-port
it to the OpenTracker yet, but I'm working on it.  If anyone has a station
they want to test out (plus an OpenTracker or T2) let me know.

Scott
N1VG







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