Re: tuned coils

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, February 17, 2001 12:48 PM
Subject: Re: tuned coils


> Original poster: "Drew Murray by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<drewallmighty-at-hotmail-dot-com>
>
> Robert,
> I have about a years experience with TCs and i have heard much on the
> transmitting recieving bit. All i have heard is that you can do something
> with an old satalite dish or a cooking wok to "focus the energy. I have
> never tried this but in theory it should work.

In theory, it WON'T work, at least not for doing any focussing at TC
frequencies... Parabolic reflectors, in order to do any good, need to be
large in terms of wavelengths.  The old sat tv dish is designed for
"C-band", roughly 5 GHz, or a wavelength of around 6-8 cm, so that 3 meter
diameter dish is 30 or more wavelengths in diameter.  The little "Wok sized"
DBS dishes work at Ku-band, where the wavelength is around 2-3 cm, so the 50
cm dish is some 20 wavelengths across.

Most Tesla coils run at a few hundred kHz, where the wavelength is on the
order of 1000 meters.  It's gonna take a huge reflector to do any good for
focussing (Even Arecibo isn't that big).

 I have also heard that
> vacuume tube tesla coils are excelent transmitters as small ones can light
> up a luminous tube at greater distances than most medium sized TCs. They
are
> supposed to produce a lot of RF. Something was mentioned about not
touching
> metal objects while the VTTC is operating as they may give you a shock or
rf
> burns. this also supports the VTTC is a better transmitter theory. I
assume
> that you know about big toploads to transmit, right?

This is potentially true... A VTTC might be a better RF source, although I
had a length discussion with some tube guys about this, and the upshot was
that overall, a spark gap is a pretty efficient switch, and if you are
concerned about "wall plug power  to RF power" efficiency, the sparkgap
transmitter might be more efficient (as well as being a LOT simpler).  Even
a really good Class C amplifier is going to be hard pressed to do better
than 60-70% efficiency, and that's without taking into account the losses in
the PS, etc.
> Anyway, i wish you luck and let me know about your progression on this
> project.
>                                                           Ciya,
>                                                      Drew Murray
>
>
>
> _________________________________________________________________________
> Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail-dot-com.
>
>
>
>