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[aprssig] TNC-2 tuning and temperature stability

Robert Bruninga bruninga at usna.edu
Sun Mar 12 04:36:38 UTC 2006


>>> scott at opentrac.org 03/11/06 11:05 PM >>>
>I also discovered that the tuning comes out almost 
>perfect with the adjustment pot set dead center, 
>I'm wondering if there's really any need to include 
>it at all..

My thought would definately be yes.  Beacuse most parts
are all in tolerance, and errors may cancel, but some
assemblies might have all high or all low tolerance and
the accumulation may be far enough off that you need the
pot to bring it in.

>One other thing I'm meaning to explore is exactly how useful 
>the passive filter network really is. 

I'd say very... on some radios.  Maybe some radios dont need it,
bt others with lots of distortion generating intermod may need
it badly.  Best not to base a design on an assumed "good" radio
only....

de Wb4APR





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