WHy only those 3 radios? Cannot any 2m rig with any [TNC] or one of their other devices, or even
a venerable kpc3+, digipeat?
Yes, but it is all about risk. Generallly, 90% of all packet radio/TNC's on the air are misconfigured in someway or another. It has been this way for the last 40 years of packet..., and although they "work" some suffer as much as 20 dB or more loss of weak signal performance (but no one notices because it "works"). Most are just plug-n-play till it "works" with no attention to levels, deviation, clipping, compression, skew, balance, bandwidth, pre-and de-emphasis, etc.
When trying to do a one-time long-chain national test, the risk of a single station not meeting 100% optimum settings and causing the whole test to fail is just too high. The kenwoods may not be the perfect of any of the above settings, but they are factory consistent and beyond the owners abilty to screw up. And they are very sensitive to each other, able to decode each other's packets down to only 3 bars (about -116 dBm) where as some TNC's and Trackers must have 60 dB over S9 full scale dead full quieting signals before they are decoded. Yet their owners claim "the work"...
All you need is an APRS radio that can digipeat (D72, D700, D710) and a power source and antenna. (and Know how to operate it!)
And said another way, These radios all use a flat passband and most all TNC/Radio combos use pre and de-emphasis. I'm not saying one is better than the other, but we must have consistency. Many Many dB of weak signal performance is lost when one tries to talk to the other.
Thanks Bob, WB4APR