On Sep 26, 9:56 am, "Wayne" wrote:
"Nate Bargmann" wrote in message
news
On Sun, 23 Sep 2007 12:59:49 -0500, Richard Fry wrote:
"Rick wrote
... What say you all?
Read "Ground Systems as a Factor in Antenna Efficiency" by Brown, Lewis
& Epstein of RCA Labs, published in the June, 1937 issue of The
Proceedings of the I.R.E.
It proves otherwise.
Honest question, does it matter whether the objective is a strong ground
wave as in AM broadcast or skywave as in amateur operation?
I am installing a Hustler 4BTV this fall and have put down (so far) 16
radials that range from about 18 to 35 feet in length due to my servere
space restrictions. I may add 16 more later this fall as an experiment.
73, de Nate
It would be interesting to follow the change in VSWR as you add individual
radials. Some years ago, there was a discussion of adding radials until the
VSWR stopped increasing. This was based on an expected feedpoint resistance
of 36 ohms, and an assumption that the ground losses were 15 ohms or less.
So at the worst case, the VSWR was near 1:1. The best case, with a ground
loss approaching 0 ohms, would have a VSWR of 50/36= 1.39:1.
I want to attribute the original discussion to W2DU, but I stop short of
that, in case I don't remember correctly.
I think it would be a lot MORE interesting to follow the change in
_impedance_ as you add wires. I can see a lot that can go wrong with
"adding radials till the SWR stops increasing." I don't think that
the case of 33 ohms ground resistance is one to seriously consider*,
but if you're operating over really poor ground and/or your "quarter
wave" antenna isn't really a quarter electrical wave, you may see
significant reactive component that you'll never resolve with an SWR
meter. You'll likely get very confused by it instead.
*What's the "ground resistance" with as few as two radials, even if
there's no earth ground nearby? What if there are no radials but the
ground is really awful? Some "what-ifs" with EZNEC or the like can
give you an appreciation for what happens...
Cheers,
Tom