getting shunted to the ground. Xbees are shielded but Marcy 1's aren't. In any case, range is far less than 72Mhz. Frequency doesn't matter.
After trying many antennas, the receiver antenna doesn't matter. It works without an antenna. The transmitter antenna is required. The best one has been a loop with no balun. Dipoles are 2nd. Monopoles with the balun suck. Unless you've got an amplifier, skip the monopole.
Loop antennas got us a big improvement but still not the same range as the 1st 2 boards.
The double sided board for telemetry goesmuch farther than the single sided board for RC so maybe double sided boards were the key.
Fuggedaboutit. That actually degraded performance. Next tried isolating the transmitter from the remote control.
That didn't do any good either. It's coming down to silicon defects.
So when you get the radios optimized, what happens but CPU overloading when all systems are running. The problem is fixed packet sizes of 100 bytes take too many clockcycles on the ground station so you really need variable packet sizes as shown in the MRF49XA reference software.
In any case, just think how radios once required huge coils & half a circuit board like your 72Mhz remote control. Never thought we'd solder chip radios on our own boards.
1 day with better radio performance got us the 1st autonomous flight out of Marcy 1. Not much of an autonomous flight but no-one ever documented an autonomous monocopter before.
You really can't get much done when working 50 hours/week & sitting in traffic another 10. No surprise Parrot Cellular whipped out WiFiquad rotors with a full time staff while you were still warming yourboss's seat.