On Mon, 20 Apr 2015 19:16:55 +0200, "bilou" wrote:

I like the idea of using a bifilar antenna with the 2 wires in parallel for
RF and the motors supplied in differential mode.
Good motors for the job could be those used in lowcost Dremel tools
They reach 20000 RPM and work on 220V AC or DC.

Ummm, the Dremel tool probably weighs too much. It would also need a
gearbox to produce counter rotating propellers, to keep the reaction
torque from spinning the motor and winding up the antenna wire. That's
incidentally why quadcopters have two rotors going clockwise, and the
other two going anti-clockwise. That's also why you don't see many 3
rotor devices.

Collector noise in receive could be a problem too.

Not to worry. Collector noise (whatever that is) would probably be
buried under the overwhelming atmospheric noise (mostly lightning) on
1.6 MHz.

May be wiring the 4 motors in serial would be a good idea too to minimise
voltage drops and weight.

I assure you that 4 motors wired in series, parallel, differential, or
a tangled mess, would weigh exactly the same.

However, you're correct that voltage drop would be a problem because
the device really sucks power out of the LiIon battery. My quadcopter
uses a 2200 ma-hr battery for 15 min maximum flying time. Assuming I
drain it completely:
2.2 A-hr / 0.25 hr = 8.8 A drain
The 16AWG wire might handle that, but with about several ohms of
copper loss, most of the energy will go into heating the antenna.
Sorry, but I'm late for a free lunch so let someone else calculate the
resistance of 40 meters of 16AWG wire.

Incidentally, the battery is rated at 25C, which means that it can
theoretically drain at:
2.2 A-hr * 25 = 55 amps
https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=26472
Yes, you can weld with the battery.

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

On 4/19/2015 2:17 PM, Jeff Liebermann wrote:
On 19 Apr 2015 10:45:10 GMT, Rob wrote:

But do you want a radio controlled gadget with 4 electric motors at
the top end of your vertical?

A drone would work, but does not have enough battery capacity to be
able to keep the antenna in place for more than about 10-20 mins.
Longer would require seperate power wires, which would interfere with
the radiation pattern.

Weight might be a problem. I'll guess(tm) #16 AWG wire, which weighs
7.82 lbs/1000ft or 11.6 gm/meter. 1/4 wave at 160 meters is 40 meters
so that antenna would weigh:
11.6 gm/meter * 40 = 464 gm
Hmmm... Probably too heavy. By comparison, a GoPro camera body weighs
100 gm. Ok, smaller guage wire or bigger quadcopter.

Did you read the OP? He discusses all of the above and suggests a way
to work around.

--

Rick

On Fri, 24 Apr 2015 08:11:20 -0400, rickman wrote:

Did you read the OP? He discusses all of the above and suggests a way
to work around.

Yep. He talked about using 1kV at 10KHz to somehow control the drone.
That's rather impractical, so I supplied what I thought might be more
practical methods and some numbers as a sanity check.

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

Jeff wrote:
On 18/04/2015 17:58, wrote:
gareth wrote:
This current interest (and privacy furore) about drones set me thinking,
what an interesting way to elevate a TopBand vertical, but being a temporary
structure, not breaching any planning permission (Brit) or zonal (Yank)
restrictions.

However the height of a 1/4 vertical would be such that it may fall
under the regulations of the CAA (UK) and the FAA (US) depending on
the location.



Under 60m (~200') does not require any permission in the UK.

Jeff

I didn't say anything about "permission", I said regulations, and you
may want to check the fine print, e.g. the FAA has language about 200
feet AGL within 3 nautical miles of an airport, which is why I said
"depending on the location".

And if one is thinking about a balloon or kite antenna, the FAA also
has language about within 5 miles of an airport and visibily of less
than 3 miles.

I am sure the CAA has similar fine print.



--
Jim Pennino

On Sun, 19 Apr 2015, wrote:

Jeff wrote:
On 18/04/2015 17:58, wrote:
gareth wrote:
This current interest (and privacy furore) about drones set me thinking,
what an interesting way to elevate a TopBand vertical, but being a temporary
structure, not breaching any planning permission (Brit) or zonal (Yank)
restrictions.

However the height of a 1/4 vertical would be such that it may fall
under the regulations of the CAA (UK) and the FAA (US) depending on
the location.



Under 60m (~200') does not require any permission in the UK.

Jeff

I didn't say anything about "permission", I said regulations, and you
may want to check the fine print, e.g. the FAA has language about 200
feet AGL within 3 nautical miles of an airport, which is why I said
"depending on the location".

And if one is thinking about a balloon or kite antenna, the FAA also
has language about within 5 miles of an airport and visibily of less
than 3 miles.

I vaguely recall reading about rules for antenna height near airports.

Michael

I am sure the CAA has similar fine print.



--
Jim Pennino

"Michael Black" wrote in message
ample.org...

I vaguely recall reading about rules for antenna height near airports.

In Brit, not exceedng 50 feet within 1/2 mile of any runway, ISTR.

Jeff wrote:
On 25/04/2015 05:32, gareth wrote:
"Michael Black" wrote in message
ample.org...

I vaguely recall reading about rules for antenna height near airports.

In Brit, not exceedng 50 feet within 1/2 mile of any runway, ISTR.



That clause hasn't been in the UK licence for about the last 30 years.

Jeff

Perhaps not, but is there not local authority/planning regs that restrict
mast and/or antenna height within x distance of airports? I'm sure I read
that a while back when researching putting my own mast up (didn't do it in
the end), I'm only about 2 miles from Rochester airport so it stuck in my
mind.

--
STC // M0TEY // twitter.com/ukradioamateur

On 2015-04-18 08:38:31 +0000, gareth said:

This current interest (and privacy furore) about drones set me thinking,
what an interesting way to elevate a TopBand vertical, but being a temporary
structure, not breaching any planning permission (Brit) or zonal (Yank)
restrictions.

One problem would be the flight time / battery life, so one approach
could be to power the drone through the antenna cable (much as with
mast-head preamps), in which case, being tethered, it would no longer be
a drone!

The power considerations, however, would call for too heavy a cable to
be lifted
aloft, so, taking the cure from the electricity grids, perhaps the solution
would be to power with 1kV AC (say, 10kHz, to reduce the sizes of
aloft transformers) going up a twin feeder, with the top band excitation
driving both of the AC feeder wires in parallel?

(Not too dissimilar in principle from the electicity grid using Pilot Tone
protection)

Gareth G4SDW

PS. By varying the frequency and / or phase of the 1kV AC, the
positioning of the ex-drone woulc be controlled thatway.

How about a tethered helium balloon instead? This way you don't have
to worry about powering the thing. Bell wire will handle 100 watts all
day without turning into smoke.

You could use some SpiderWire kevlar fishing line to make a few tethers
so that the balloon doesn't whip around too fiercely in the wind, and
it would require no power at all.

In message , Oregonian Haruspex
writes



How about a tethered helium balloon instead? This way you don't have
to worry about powering the thing. Bell wire will handle 100 watts all
day without turning into smoke.

Many amateurs would give their right arm for a functioning helium
balloon. It's the sort of thing that most LF band aficionados can only
dream about. It's a lot easier to obtain electricity than helium.




--
Ian

Ian Jackson wrote:
In message , Oregonian Haruspex
writes



How about a tethered helium balloon instead? This way you don't
have to worry about powering the thing. Bell wire will handle 100
watts all day without turning into smoke.

Many amateurs would give their right arm for a functioning helium
balloon. It's the sort of thing that most LF band aficionados can only
dream about. It's a lot easier to obtain electricity than helium.




Then I guess the solution would be an electric balloon! :-)

de Irv VE6BP