On Mon, 20 Apr 2015 08:14:29 +0100, Ian Jackson
wrote:

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

Good point. That should work, but I would feel better if the
quadcopter were not at RF potential. I don't want to find out that it
doesn't work when I key the transmitter when the quadcopter is 40
meters in the air. There's also a small chance that some of the
wiring in the quadcopter will pickup RF from the antenna independent
of the power/antenna wiring, which might cause some havoc. Different
problem, where more RF chokes might be needed. I guess I could just
fly it around an AM BCB transmitting antenna and see what breaks. The
only problem is that the local AM transmitting antennas are surrounded
by water.

Incidentally, the biggest quadcopter helistat of them all:
http://en.wikipedia.org/wiki/Piasecki_PA-97
A helium filled ZPG-2W dirigible and 4 old H-34J helicopters
underneath. It was designed to lift 26 tons of logs out of the
forest.
https://www.youtube.com/watch?v=_7jENWKgMPY
Oops.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558