Ron Youvan wrote:
>
> I disagree! Quarter wave antennae REQUIRE a counterpoise' to produce an
> equal but opposite `image' of the elementto be an ANTENNA. Two quarter WL
> antennae stacked with the feed points together produced a dipole A pipe in
> the ground is not a counterpoise, because of the high resistance of the
> dirt. (salt water excepted)
> 37 + 37 = 72 OHMS
Well, Quarter wave antennas do not require a counterpoise. That
"equal and opposite" image will be formed, in solid concrete, if
you place it there. I think what you mean to say is that radials,
(which is exactly what K4JRB said )
enhance the image. As for your 37 ohm figure, that is reached in
a 1/4 wave vertical ONLY when sufficient radials are present to
for all practical purposes
for an almost perfect image. As for your 37+37 ohms, the center
impedence of
a 1/2 wave vertical dipole fed in the center is nowhere near 72
ohms.
> A vertical half wave element (which can be feed at either end with proper
> matching, if you wish) can be elevated any amount you wish , if over the
> houses and trees this will reduce the effects of the ground clutter, is
> unsurpassed. IMHO
Try feeding a 1/2 wave element at the top. You've still got to
have a ground return, and I'll guarantee you'll never match it. I
must be missing something here. This is gibberish. And what
ground clutter are you referring to?
>
> If you don't match the 5 k or so input impedance it won't. Radials do
> little, to a dipole, but change the radiation angle, and possibly detune it
> comparing it to it's `mounted high away from everything frequency.'
Again, you're throwing numbers around without regard to facts.
The feedpoint impedence of a 1/2 wave vertical fed at ground
lever will vary depending on the thickness of the wire vs the
frequency. Typical values WITHOUT radials run several thousand
ohms with very thin wire, but try throwing in just a few radials
and see how the radiation resistance drops. You seems to be
missing the point that in all vertical antennas, a path must
exist for ground return, and the lower resistance that path
exhibites, the better the antenna will perform.
Now as a matter of efficiency, a typical 1/2 wave with an before
matched resistance of around 1500 ohms is far supperior, but ONLY
in the matter of efficiency. Or has Ohms law been repealed again?
-------------------------------------------------------------------------
> 73 (= Best Regards) de: Ron ka4inm@qsl.net
----------------------------------------------------------------------------
I would seriously suggest you read a little from the works of Jim
Lawson, or Paul Lee.
73
Ed
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