"Cecil Moore" bravely wrote to "All" (02 Apr 05 09:57:02)
--- on the heady topic of " Antenna wires and ferrite"

CM From: Cecil Moore
CM Xref: aeinews rec.radio.amateur.antenna:27806
[,,,]
CM Adding the insulation increased the feedpoint impedance from
CM 57 ohms to 65 ohms which means the forward and reflected
CM waves on the standing-wave antenna were attenuated more
CM using insulated wire and sure enough, using that particular
CM insulation reduced the EZNEC maximum gain by 0.12 dB.

CM Many people have noticed shifts in resonant frequency when
CM their antenna gets wet. Water has a dielectric constant
CM around 80.


Speaking of odd antennas, how about using a long neon tube as an
antenna and what would eznec give as values then? After all a plasma
behaves like a conductor doesn't it?

A*s*i*m*o*v

.... Email returned to sender -- insufficient voltage.

Asimov wrote:
Speaking of odd antennas, how about using a long neon tube as an
antenna and what would eznec give as values then?

Back in college, we used to use a florescent bulb
to detect RF electric fields. What's the feedpoint
impedance of a neon tube?
--
73, Cecil http://www.qsl.net/w5dxp

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"Cecil Moore" bravely wrote to "All" (03 Apr 05 08:38:34)
--- on the heady topic of " Antenna wires and ferrite"

CM From: Cecil Moore
CM Xref: aeinews rec.radio.amateur.antenna:27837

CM Asimov wrote:
Speaking of odd antennas, how about using a long neon tube as an
antenna and what would eznec give as values then?

CM Back in college, we used to use a florescent bulb
CM to detect RF electric fields. What's the feedpoint
CM impedance of a neon tube?

I suppose the plasma looks like a DC resistance over a region of its
characteristic and maybe even negative at some point. It depends of
course if we are talking about a glow or an arc. With an arc the
current discharge is somewhat infinite and the huge noise makes it
impractical. I'm not sure about the noise with glow discharge on a
long neon tube but I'm assuming it is very low judging from some brief
measurements I made on a neon indicator bulb. BTW these make good UV
detectors wrapped in aluminium and biased at the conduction threshold.
I'm only guessing the long neon tube has a DC resistance of about 50
ohms per foot. Something 30 feet high would therefore be around 1.5K.
What are typical running voltages and currents for neon signs?
BTW don't know if running 1KW would it make a fabulous light show?
Shades of Nicolai Tesla!

A*s*i*m*o*v

.... Speeding doesn't kill people... Stopping really fast does!