Subj : Antenna
To   : Mike Ross
From : James Bradley
Date : Sun Jul 24 2005 05:06 pm

MIKE ROSS wrote to James Bradley, "Antenna" on 07-06-05 10:56

 MR> "James Bradley" bravely wrote to "Mike Ross" (24 Jul 05  00:18:16)
 MR>  --- on the heady topic of "Antenna"

 JB> MIKE ROSS wrote to TOM WALKER, "Re: Antenna" on 07-05-05 22:44
 MR>  The only radios that work at the best they can are
 MR> those with a balanced antenna because the ground is is not needed.

 JB> Correct me if I'm wrong, but doesn't a balanced design have a
 JB> 'virtual ground' roughly between the points that the wires diverge?

 MR> Virtual means imaginary. It is just a mathematical curiosity.
 MR> Grounding that point won't make a difference at all. Consider a
 MR> balanced antenna in deep space, there is no ground to be found
 MR> anywhere but it still works as well as on Earth. Now an unbalanced
 MR> antenna can also work but it must be supplied an artificial ground or
 MR> "counterpoise". This consists of at least 2 radials establishing a
 MR> ground plane opposite the antenna. In effect the combination of
 MR> unbalanced antenna and counterpoise behaves like a balanced antenna.
 MR> Mobile antennas like CB's & taxis are a familiar example.
 
You know, I always assumed the car was their reference to earth. Sure,
 they are static generators but it never occurred to me that the
 chassis mount was all for the transmission line. 

Would a TV transmission suffer from S-N while in a vehicle? I would
 assume those too would be a balanced antennae you see on Limo's. 


The way I remember first hearing about this 'virtual ground' (Please,
I can hardly, vaguely paraphrase, so...) is that the "balance" is like
a weights' centre of gravity. Electrically, there HAS to be a null point
where a person should be able to introduce infinite interference,
provided it is *only* at a theoretically impossible point source, that
doesn't propagate past this infinitesimal point... ... ... Some
bla-bla about the more null points, the more you need to engineer your
antanae... 

I hope my limited understanding, and the *decades* ago I read this
doesn't fog my point. (Second unintentional dumb pun in so many
messages.) It wasn't meant for you to shave down a needle until it was
microns thin, and solder it to a water pipe. <G>

 MR>  M*i*k*e

 MR> ... Fido, the very best source of technical advise.
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