In message , Jeff Liebermann
writes
On Sun, 19 Apr 2015 20:00:49 +0100, Ian Jackson
wrote:





With a little ingenuity, there's no reason why you couldn't feed DC
'line power' up the antenna wires (or, more accurately RF up the power
wires).

I'm sure it can be done. I'm not so sure the added weight of the
insulation and isolating chokes at the top will be tolerable. A 1.7
MHz RF choke is not a small or light weight device and this thing will
need two chokes at the top. Also, there's another reason for the
10-15 minute limit. The motors do get rather hot after a flight.
Running them continuously from a tether wire might cause a meltdown.

Would you need a power extractor at the top end? The whole copter could
simply ride on the RF voltage, ie a bit like a bird perched on a
high-voltage power line (assuming that the copter electronics were
happy). Even if you had zero-weight power extraction chokes etc, I doubt
if it would make much difference
--
Ian