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RE: LF: Tesla Coil as an antenna

To: [email protected]
Subject: RE: LF: Tesla Coil as an antenna
From: "Tom Tishken KD4WOV" <[email protected]>
Date: Thu, 31 Jan 2002 18:15:03 -0500
Importance: Normal
In-reply-to: <[email protected]>
Reply-to: [email protected]
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Wow, now that is something I have not heard. I had a Jacob's Ladder set up
that created some RFI even into the TV bands. I am amazed that you did not
hear anything, but you could be right about the energy being dissipated in
the sparks. I had an HF antenna that had a bad insulator. It worked great at
25 watts but at 50 watts the SWR started going crazy and very few locals
could hear me that were 5 miles away (on 10 meters). What took a while
figure out, was it worked at lower powers but it seemed to be an attenuator
at higher power levels when it started arcing (which I found out about by
seeing it at night).

Makes you wonder how Tesla could have sent any power over any distance
except 2 possibilities. 1) He had a large ground, which would be very
effective at LF and we have not reproduced. 2) He made sure Arcing was not

-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of g3ldo
Sent: Thursday, January 31, 2002 5:39 PM
To: [email protected]
Subject: Re: LF: Tesla Coil as an antenna

>>   I have not experimented in a while with my partially built tesla
>> but has anyone used their Tesla coil as an antenna for ELF or other

I assume that a typical tesla coil is a rather short and fat structure. I
am not sure that in this case the magnetic field can be ignored, compared
to the electric field. And since a Tesla coil has rather small
dimensions -
compared to other LF transmitting antennas - I'm afraid that it will have
very low efficiency.
BUT ... since you have the Tesla coil available I would certainly
to do some tests (that's what all the fun is about).
Over two years ago I reported on the Tesla coil as a radiator.
I was operating at radio station at Amberley Museum and was told that there
could be some QRM because of a Tesla group who had set up at the Electricity
Hall. I did not experience any QRM so after my operating stint I drove my
car near to where some of the larger coils were being tested. I was told by
the group that the frequencies in used depended on the size of the coil with
the large ones on about 130kHz and the one very big one on 70kHz.
These coils produced some very spectacular displays. I had my old 707 rig
with a converter with me and used a 2m length of wire as an antenna. The rig
was located about 100m from the coils. I tuned around the LF bands while
some of these monsters were being fired up and heard - nothing!
The receiver was working because I could hear the lager commercial stations
without difficulty.
It could be that all the energy was being dissipated the spark - but I would
have expected to receive something.
All these big coils were using the rotary spark gap method of firing the
primary coils - a spectacular display in themselves.

Peter, G3LDO

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