I'm getting ready to install my tree mounted 80 m vertical now that the
ground is thawing.

It will be a 1/4 wave vertical for 80 meters.

I have a question regarding the radials I'll be putting out. I was
planning on using solid #12 copper, and was going to lay out about 500
feet total of radial.

Am I better off to use fewer and longer, or shorter and more? I'm
inclined toward 10 50 foot radials. I have heard opposing views on the
"proper" length of radials. (I'm assuming that longer and more would be
much better, but I have some practical considerations here)


- Mike KB3EIA -

Mike,

I assume you will have ground surface or shallow buried radials.

There are hardly any resonant effects in shallow-buried radials so no need
to concern yourself with particular lenghts.

You will be far better off with more and shorter wires. The attenuation
along radial wires is quite high. There's no current flowing in them beyond
a small fraction of a wavelength from the focal point. They may as well not
be there.

Wire diameter selected solely on your ideas about durability. Enamelled
copper wire is fine and may be less expensive, easier to obtain than the
bare stuff.

Not much point in having radials longer than 1/10th or 1/15th wavelengths in
moderately good soil at the lowest frequency of interest. A little longer
in poor soil. Shorter in very good soil. Moisture content and fertility is
the guide.

Begin with one radial and increase the number by 50% until the RECEIVED
signal strength from lower frequency, stable, reliable transmitters stops
increasing. Then add a few more for luck. You will probably end up with
fewer radials than recommended in the handbooks.
----
Reg, G4FGQ

Reg Edwards wrote:
Mike,

I assume you will have ground surface or shallow buried radials.


They will be shallow buried.

There are hardly any resonant effects in shallow-buried radials so no need
to concern yourself with particular lenghts.


You will be far better off with more and shorter wires. The attenuation
along radial wires is quite high. There's no current flowing in them beyond
a small fraction of a wavelength from the focal point. They may as well not
be there.

Wire diameter selected solely on your ideas about durability. Enamelled
copper wire is fine and may be less expensive, easier to obtain than the
bare stuff.

Okay, I thought I heard something about this in here somewhere! So I can
use insulated wire? I do have some #12 insulated solid wire - it's of
the house wiring type, with a relatively hard insulation on it. I don't
know if this would work or not, but it would seem to make things last a
lot longer. and I wouldn't have to buy more nekkid wire.

Not much point in having radials longer than 1/10th or 1/15th wavelengths in
moderately good soil at the lowest frequency of interest. A little longer
in poor soil. Shorter in very good soil. Moisture content and fertility is
the guide.



Begin with one radial and increase the number by 50% until the RECEIVED
signal strength from lower frequency, stable, reliable transmitters stops
increasing. Then add a few more for luck. You will probably end up with
fewer radials than recommended in the handbooks.

Thank you much!

- Mike KB3EIA -

Mike,
Relatively thick plastic insulated wire will do fine for shallow-buried
radials.

Funnily enough, they result in slightly lower input loss resistance. (If you
take them out of the ground entirely, so that they behave as elevated
radials, you get a very low loss of course and with strong resonance
effects.)

Thick plastic insulated buried radials will have slightly greater resonance
effects than bare or enamelled wire which have next to none. They will also
have lower attenuation in the ground. In principle they could be made
somewhat longer than the equivalent bare wires. But as the length of bare
wires is all wishy-washy anyway you can forget about it. Go ahead and lay
it.

By the way, on 160 and 80 meters, if the shape of your property is suitable,
include your domestic plumbing system in the radial system. The best radial
you have is the incoming metal water main pipe. ;o)

At present I have a 160m inverted-L. Had it for years. The ONLY radial is
the domestic incoming main water pipe. At one time there were 7 other
radial wires of various lenghts around the garden but these were all
disconnected when part of the garden was paved with concrete slabs. I
noticed no difference in performance with the solitary but very good
water-pipe radial.
---
Reg.

It will be a 1/4 wave vertical for 80 meters.

I have a question regarding the radials I'll be putting out. I
was planning on using solid #12 copper, and was going to lay out about
500 feet total of radial.

Am I better off to use fewer and longer, or shorter and more?
I'm inclined toward 10 50 foot radials. I have heard opposing views on
the "proper" length of radials. (I'm assuming that longer and more
would be much better, but I have some practical considerations here)

If you only use that much wire, go with shorter. However, you will want
to put down quite a but more wire than that to get good performance.

The rule of thumb I use is a minimum of 50 radials, with length
at least the length of the vertical.

I currently have up a similar antenna- a full size wire 80m vertical
hanging from a tree fed in parallel with a 160m inverted L. So far I
have about 65 radials ranging from 50' to 100' in length. The antenna
works great on 80, even for far DX such as 9M6. On 160 it is fairly
good, but I feel I still need more radials.

Torsten
N4OGW

Mike & Reg,
I agree with Reg, mostly. A good 'rule of thumb' (for
me), is put in as many radials as you can before you get
sick and tired of it, then do one more. Considering that
my knees give me problems, that usually works out to ~far~
less than the 'normal' number of radials.
I don't exactly disagree with Reg about the domestic
plumbing being used for an RF ground, but there are a lot
of 'if's about that. The one 'if' that I've had a problem
with is that if the plumbing happens to be shared with
neighbors, you have a direct RF path into their house, and
their electrical appliances, and they usually know just
who's door to pound on. That may have been an isolated
occurence,
but something to keep in mind if the "pounding on the door"
happens.
What kind of wire? The 'best' wire type to use is what
ever you have the most of. And the 'best' way to tell if
there are enough radials is when there is no noticable
improvement after adding the last few that you put in. Then
put in maybe a few more just for the hell of it...
'Doc