Re: NEC-LIST: Plasma Antennas

At 01:25 PM 5/4/2004 -0700, you wrote:
>In a message dated 5/3/2004 9:48:38 AM Pacific Daylight Time,
>rsmueller_at_netzero.net writes:
>
> > Hello to the group,
> >
> > I was wondering if anyone on the list has seen any of the new "Plasma
> > Antennas" that Markland is advertising? I fundamentally understand how a
> > plasma antenna could work, but, I am not convinced in it's performance
> > claims: i.e. varial bandwidth, electronic scanning, etc. Has anyone
> built a
> > practical plasma antenna to date?
> >
> > Roland Mueller
> >

I'm somewhat skeptical of:
    * After the gas is ionized, the plasma antenna has virtually no noise
floor
(from the third page of their web description)

Plasma is hot (even if the gas is at very low pressure), and so, will
radiate some energy.

It would be interesting to see the final reports from their ONR contracts.

On web page 4, they allude to "lower collision rates among its charge
carriers... calculations show that this means less noise" Presumably,
they've measured it, what are the numbers?

As far as the claims of variable bandwidth and scanning, they're all
feasible. Think of the plasma as a switchable conductor. One could build a
large reflector that looks like a plasma TV, and turn on and off pieces of
it to change the electrical "shape" of the reflector. One could, for
instance, make a lens or reflector with a variable grating spacing.

Overall, it's a clever idea. Whether it's practical (especially for
receivers) is another story entirely.

I note that one of their patents is for an ELF receiver antenna. You're
probably not too concerned about receiver noise figure at those
frequencies, since environmental noise will dominate.

The idea of using a plasma as a reflector of RF is nothing new. They
mention Radar T-R tubes in one of their patents.

One could fairly easily test their ideas with ordinary neon sign technology.

James Lux, P.E.
Spacecraft Telecommunications Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875

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