[aprssig] Voice Repeater Frequency SPec

[Robert Bruninga]

> In addition to the existing Tnnn, Dnnn, 
> these were added:  1750 and NoPL.

Humm...  I don't feel comfortable with CSQL for some reason,
just not sure most hams would immediately recognize it.  Not
wanting to belabor the point.  But another possibility is simply
"Open".

But in any case, it does not matter.  We are trying to
standardize on what the radios or sofware can parse.  And so we
must agree on the T###, D### or 1750 standard, but anything else
can mean "no tone required" since if it is not a T### or D### or
1750, then there is nothing the radio has to do to use it
anyway..

> http://www.ew.usna.edu/~bruninga/localinfo.html
> http://www.ew.usna.edu/~bruninga/aprs/freqspec.txt

I still see many examples trying to stuff T107.3 decimal points
in there and T88.5 type entries.  Those are the ones we need to
tweak...

> And if you have no PL and no tone, then those 4 
> bytes may be used for other purposes.  

But only if needed.  I'd prefer that the 4 byte field be
retained for the squelch field even it it is not required just
so it keeps the rest of the format rather standardized...
Meaning, I guess use "NoPL", "open" or "CSQL" (though I don't
prefer the last one)...

> Bob, WB4APR