Hi Dave, LF,
Yes, i know about these problems with wet braids. It is not only a problem of
kite antennas. I had the same problem on my LF QTH in 2003. As mentioned i
think a very well suited material is teflon. This is often used in HV
applications when light weight is a question. Maybe i use some additional
braid, say 0,5m between the kite carrying braid so if it melts, just the wire
and not the kite falls down.
Tnx for your hints.
73, Stefan/DK7FC
________________________________
Von: [email protected] im Auftrag von Dave Pick
Gesendet: Mi 10.03.2010 17:56
An: [email protected]
Betreff: Re: LF: KITE ANT
Stefan
Just one warning, I have used kite-supported aerials on 136 many times and you
have to be careful what insulating material you have between the kite and the
top of the wire. One day the kite was flying well but there was a little rain,
I transmitted and the wire fell out of the sky and the kite fluttered down
(fortunately I could find it!). When I looked to see what had happened the thin
rope holding the wire to the kite had burned through because the rain had made
it conductive. I think monofilament fishing line may be better...
Dave G3YXM
----- Original Message ----
From: Stefan Schäfer <[email protected]>
To: [email protected]
Sent: Wednesday, 10 March, 2010 12:06:06
Subject: Re: LF: KITE ANT
...In Germany you can use a maximum braid length of 100m without a special
licence. If 200m would be allowed, my vertical would be a 200m ;-)
But with a special permission you can relatively easy go up to 300m! I still
try to get that permission for the next weeks. Then, the VLF signal would even
be more than 10dB stronger, what would give the chance for the UK to get the
VLF signal, i hope so...
Static HV dangers are well known to all of us i assume. But the upper kV range
is nothing mystic. 10kV is just a factor 10 of 1kV, just like 10V is a factor
10 of 1V. You can die if you touch a 10kV power line or if you touch a 100kV
power line. So there is just that rule: Do not touch when under voltage and
assure that there can be no voltage when you think that there is no voltage
(measuring, earthing during operating). I've worked almost 6 years in the HV
group of the institute of electrical energy systems
(http://www.hst.tu-darmstadt.de/index.php?id=10&L=1) and had almost each week
to work with voltages well above 20kV (up to 3MV, 1,2/50µs), so i think i have
the necessary respect without beeing afraid or careless. On my hill there are
no schools, no roads and no neighbours but i will keep in mind what you caution
on! :-)
73, Stefan/DK7FC
Am 10.03.2010 09:16, schrieb [email protected]:
> Hi all
>
> May I ask you to pay some attention on the three following issues related to
> balloon/kite aerials ?
>
> - using "high" altitude kites or balloons is often subject to a formal
> authorization (at least in France, and specially if you expect to use the
> aerial close to an airfield)
>
> - even when weather is very good, very high DC voltages (many kV) can appear
> (from natural local electric field) on the antenna wire. DC grounding of the
> wire is therefore mandatory
>
> - avoid any AC HV lines (or schools, or roads, or irritable neighbours) in
> the vicinity of your experiment area.
>
> Regards
>
> Jean-Louis F6AGR
>
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