For US Fire people--NFF tones
 

As a reminder to those flying in the US on fires, it is time to put the 110.9 tone on the NFF RX channel.

IA Tech Bulletin 2010-2

tones
 

Hi Gordy.
Having been involved with CTCSS tone implantation on existing ground radio systems over the last 30+ years, the last radios RX to be tone protected is always the base\ ground control, hopefully at least the controller can hear all transmissions.
The 2 stage changing of radios is a real nightmare + costly, & leading to further chances of faults developing.
The other problem is CTCSS or DCS does not remove the interference only masks it, if you share frequencies you will get break through unless the tone delay times are VERY VERY fast, & interference level low.
The nuisance level to user will be reduced, but you can still get heterodyne, and the break through of the interference voice, data, or just ambient noise.
Digital is the way to go but that has its own problems with coverage, cost, & implementation

500e

All US fire fighting aircraft are using digital as of this year---expensive retrofit as we have 5 aircraft each wiht two Fm radios, and all our support vehicles. We are now using the NAT NPX136D's.