Originally Posted by

On Friday, February 14, 2014 11:21:01 PM UTC-6, Brian Reay wrote:
wrote:

On Friday, February 14, 2014 1:59:15 PM UTC-6, gareth wrote:

Just found this; looks interesting; no connection with the author;



all in the spirit of free dissemination of knowledge to fellow



radio amateurs ...







http://www.cvarc.org/tech/antenna_my...enna_myths.pdf



Several parts of it are pure unadulterated horse doo-doo..

I find it to be in very poor taste to post a page claiming to

expose and list myths and mysteries, only to replace them with

other myths and mysteries. :+

That is akin to chasing one's tail while barking at the moon.



I confess to only have 'scan read' the reference and I thought it was still

pretty good.



What in particular do you have an issue with, please?



--

73

Brian

G8OSN/W8OSN

Well, I suppose most is OK, but there are a few problems.

Take this one..

More recent HF tests by Al Christman - KB8I; "Eleva
ted Vertical Antenna Systems,"
QST, August 1988, p 35; have shown that
fewer "elevated" radials will perform
about as well as 120 ground mounted ones.
A base mounting height above ground
of about 1/10 to 1/16 of a wavelength seems optimu
m for 4 radials.........but will vary
with soil conductivity.

I don't know how he ran his tests, but this is not right.
1/10 WL is way too low for four elevated radials to equal
120 on the ground. I was harping about this "myth" in
another post not long ago..

There is no free lunch. :|

For four radials to equal 120 on the ground, they will
need to be nearly 1/2 wave up. Four radials at 1/4 wave
up are equal to about 50-60 on the ground.

Seems optimum? If the radial system were optimum, it really
wouldn't matter what the conductivity of the ground was.

This is actually proving my point that four radials at 1/16
to 1/10 WL are not nearly enough to actually equal 120 on the
ground. If they were equal, you wouldn't have to raise the
antenna and radials.

That's the whole point of using so many radials on the ground.
So the quality of the ground, good or bad, really doesn't matter.
Efficiency will be high either way.

Some of his 1/2 vertical design statements could be argued
with, but I'll be here all night if I start into that.. :/

Then you have this..

Myth:
A 5/8 wave antenna has 3dB
more gain than a ground plane.
False

This can be true in many cases.
But it can also be false in many cases.


*
The losses in the required matching coil at the base
of the 5/8 wave antenna reduce the gain difference
to a max of about 2dB (with a perfect ground plane)
to zero difference in some installations. **
--------------------------------------------------

This is fairly absurd.. The loss of the loading coil
is quite negligible. I bet not even enough for most
people to accurately measure.

The coil has nothing to do with why some types of
5/8 verticals show little or no gain vs a 1/4 GP,
or isotropic.

Those are a couple of my issues anyway..
The "Free Lunch" elevated radial system being one of my
pet peeve myths.. :|