It is an FCC rule because cellphone tower are designed to
pick up a limited number of calls and at altitude the towers
are over-loaded.

I don't understand this.
Consider that many new headsets actually have a cellphone interface.

and consider that here in Canada it is not illegal, and I use mine lots
- plugged right into my headset.
I don't understand how it could be legal here if it really did overload
towers. So what is the REAL reason?

Hmmmm . . . the plot thickens



--

Tony Roberts
PP-ASEL
VFR OTT
Night
Cessna 172H C-GICE