wrote:
I disagree. Transmission lines have two conductors. Radials don't.

Roy, try using your imagination!

My "Electronics Equations Handbook" gives the specifications
for a "SINCLE-WIRE ABOVE-GROUND TRANSMISSION LINE" including
Z0, C, L, and resistivity adjusted for frequency.


Don't forget the single-conductor transmission line invented by Goubau
and named "G-Line" in his honor. Quoting from page 164 of my 1972 copy
of "The Radio Amateur's VHF Manual":

"The basic idea is that a single conductor can be an almost loseless
transmisison line at untra-high frequencies, if a suitable launching
device is used. A similar launcher is placed at the other end.
Basically the launcher is a cone-shaped device which is a flared
extension of the coaxial feedline...."

I was in error in saying that a transmission line must have two
conductors. The "G-Line" is the one exception I know of. But it
certainly doesn't function in anywhere near the same manner as a buried
radial. I'm afraid only Reg knows how his "R-Lines" work.

Roy Lewallen, W7EL

"Reg Edwards"
There are also, very common, 2 and 3-wire (3-phase) transmission lines
which have smaller radiation resistances, but radiation resistances
they DO have depending on conductor spacing.
__________

Doesn't the term "radiation resistance" normally apply to a characteristic
of antennas -- not transmission lines?

RF

I have 26 runs of 60' insulated (#14 THHN), radials on the surface, pinned
down with lawn staples beneath an 80m inverted L. The measured efficiency of
this particular arrangement is showing approximately 83%. How much more or
less efficient bare wire might be (and no one I trust has ever maintained
that there is any advantage whatsoever to bare copper vs. insulated radials
on or in the shallow ground), is a question I have not had any interest in
looking at.

I'm not about to rip them all out and put down bare copper to see if the
efficiency changes, and can think of no other way to answer the question. Of
course the absolute value of efficiency is a function not only of the number
of radials, but the quality of the earth they are laying on, so YMMV.

....hasan, N0AN
"Owen Duffy" wrote in message
...
On Thu, 19 Jan 2006 21:22:25 -0600, "David G. Nagel"
wrote:


Owen;

Given the expertise that Bill has accumulated over the years and the
good advise he has given to anyone who asks I think that your attitude
needs modification. When you were in school did you challenge your
teachers this way? I think not. If you diagreed you kept it to your self
or checked it out on your own.

Dave,

I don't agree, I have never had a teacher worth his salt who responded
to polite questions as Bill did.

No, I don't believe something just because I read it on the 'net, I
would like to know why.

For what it's worth everything that I have read tends towards placing
the radials on the open ground, usually staked down so as to prevent
tripping or getting caught in a lawn mower.

Yes, I see lots of web articles describing that in ham stations, but
it is not the only approach that I see documented and talked about.

In my limited experience, I have not seen commercial HF installations
with radial / ground wires laid above ground in preference to being
buried. The only cases I can recall were because of rock.

Whilst there are articles around about the performance of shallow
buried radials, I have not seen any that deal quantitatively with
radials laid on the ground, or pinned to the ground as you describe,
and the effects of those different installations on antenna
efficiency. That is what I was asking about.

Equally, there a plenty of articles where the author insists that
radials cannot work near the ground and they need to be some distance
above, some stating a quarter wave above.

They can't all have "better" efficiency, the only way to know is to
seek reasons why a configuration is better.

Bill proposed a "better" configuration and declined to explain why /
how it is better.

Owen
--