You're entitled to your opinion on this seemingly controversial topic.
73 / DX ..hope to catch you on the bands one day Dave

--

Charlie
Ham Radio - AD5TH
www.ad5th.com
Live Blues Music
www.492acousticblues.com




"Dave Platt" wrote in message
...
What about the Hustler antenna instructions which provide the "correct
lengths" for cutting radials? Moreover they need not be "buried 2 inches"
in
the ground but can safely remain on the ground once grass growth
effectively
buries them. Also DX Engineering www.dxengineering.com has ground radials
for sale which are "pre-cut to length". I assume they know what they are
doing. Force 12 also recommends using "tuned radials" with their line of
vertical antennas. I assume they too know more about antennas then I do.

Tuned radials are necessary and appropriate when the radials are
installed well above earth-ground level. When the antenna is mounted
up at a significant height, there's very little coupling between the
radials and ground, and the radials must be tuned in order to present
a low impedance on the frequencies of interest. Once tuned, each
radial presents a low-loss current path, and only a small number of
such radials are required.

When the radials are laid on the ground, buried, or placed a short
distance above the ground, matters are very different. There is a
great deal of capacitive coupling between the radials and the soil,
and the soil also presents a (resistive and rather lossy) path for the
current flow. As a result, two things are different:

- The coupling to the soil de-tunes the radials and greatly lowers
their Q. They no longer serve as a resonant system, and cutting
them to a tuned length is no longer essential.

- A much larger number of radials is necessary, in order to limit the
losses which occur when the return current flows through the soil.

So... in an elevated-antenna situation, as few as three or four
radials can give you low losses, but the radials must be tuned. For a
ground-mounted vertical, you need many more radials (dozens, and some
people prefer over 100), but they don't need to be tuned, and there's
not much performance difference to gain once the radials are at least
about an eighth of a wavelength.

I researched this topic before installing my 5-BTV and tuned radials were
always recommended.

For elevated antennas, that's true. For ground-mounted antennas,
tuning is simply unnecessary.

Take a look at http://www.cebik.com/gr.html which shows some antenna
modelling and graphs for vertical antennas with ground-mounted
radials. The chart of "Ground Radial Test 2" is an interesting one.
It shows that there's only a very modest difference in performance
(less than half of a dB!) between a 64-radial system using tuned
quarter-wavelength radials, and a 64-radial system using radials which
are only .15 wavelength long.

If length means nothing I could have gone with 6 inch
radials if I followed your logic...eh?

It is not true that "length means nothing". 6-inch radials are too
short to provide adequate coupling to the soil.

It *is* true that "length is not critical".

My 5-BTV installation with 72 "tuned"
radials at this page

1. http://www.ad5th.com/5-BTV.html

I am getting great reports so far but have only been on the air at this
qth
for a couple weeks.

That's good news.

The bad news is that you could have used non-tuned radials, and saved
yourself some bother and perhaps some money (used somewhat shorter
lengths of wire), and gotten equally-good reports.

You didn't hurt yourself by tuning the radials. You just invested
some effort (and perhaps some money) unnecessarily.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!