[aprssig] Freq Info for NMEA and other Trackers

[Bill Vodall WA7NWP]

>
> Simply make sure that the first 10 bytes of your BEACON text
> includes your voice operating frequency in this format
> ">FFF.FFFMHz more..." where "more..

Will GHz be supported or an additional digit for the MHz?

Also, if it's fixed format like this, the MHz would only be "cosmetic"
and not really needed.

Bill - WA7NWP