RE: How do you know if pcm radio?
Hi John,
The old Airtronics Vanguard radios where PPM for sure. PPM stands for Pulse Position Modulation. Even with 2.4Ghz, the receiver still outputs PPM to the servos.
I would think the frsky "hack" kit will work fine in an old Vanguard. I had two of those radios years ago. Bullet proof[8D]
Good luck,
Pete