Anyone know how to use square rod in modelling programs?

I'm sure it's a small effect, but I'm interested in the *proper* way to
account for it vs. round rod.

I've used the mean radius of the inscribed and circumscribed circles
and that turned out fine,
but I don't have much ability to make good gain and F/R measurements.

It seems that the corners could affect element coupling...

Should I use the circle that has the same area? Maybe the geometric
mean of the radii of the inscribed and circumscribed circles?

I've got a bunch of 1/4" square rod that I want to make 435MHz yagis
out of, and pretty much all web searches I could think of on square
antenna elements either get zero hits for being too specific or talk
about quads a lot.

The square rod is great mechanically; I can slap a piece of PVC pipe on
a milling machine, mill 1/4" slots through very accurately spaced, and
hold the elements in with cable ties.

Anyway, I'm just going to try the geometric mean and build another
antenna, but I'm interested in any comments on this.

73,
Dan
N3OX
www.n3ox.net

As they say, measure with a micrometer, mark with a crayon, and cut with an
Ax. From my limited (50 years) experience, your picking fly crap out of
pepper!

The absolute perfectly modeled antenna will still have to be adjusted in
it's environment. The difference between square and round tubing is
insignificant unless your into the mental masturbation of caring everything
out to 12 decimal places.

I am sure that someone will venture forth with an example to show how
important this is at some frequency, altitude, temperature, phase of the
moon and barometric pressure.
Such is the habit of the newsgroups denizens.

The reality is YOU have square tubing, use it and enjoy the contacts.


wrote in message
oups.com...
Anyone know how to use square rod in modelling programs?

I'm sure it's a small effect, but I'm interested in the *proper* way to
account for it vs. round rod.

I've used the mean radius of the inscribed and circumscribed circles
and that turned out fine,
but I don't have much ability to make good gain and F/R measurements.

It seems that the corners could affect element coupling...

Should I use the circle that has the same area? Maybe the geometric
mean of the radii of the inscribed and circumscribed circles?

I've got a bunch of 1/4" square rod that I want to make 435MHz yagis
out of, and pretty much all web searches I could think of on square
antenna elements either get zero hits for being too specific or talk
about quads a lot.

The square rod is great mechanically; I can slap a piece of PVC pipe on
a milling machine, mill 1/4" slots through very accurately spaced, and
hold the elements in with cable ties.

Anyway, I'm just going to try the geometric mean and build another
antenna, but I'm interested in any comments on this.

73,
Dan
N3OX
www.n3ox.net

Fred,

You are absolutely right as far as my particular antenna goes....
changing the element size by a couple of mm doesn't do anything at all
to the antenna I'm going to build.

But for high frequencies with relatively fat elements and close
coupling, maybe it does matter.

This is a question about theory; it *is* a question about the twelfth
decimal place (or is it the third? the fourth? the second?)

I'm going to build it anyway. I'm going to get on FO-29 and make
contacts with it.

I just wonder if there's a *right* way to plug square elements into
antenna modeling programs. There certainly is a right way to account
for tapered elements.

Dan,
N3OX
www.n3ox.net

To model a square conductor with a round wire, use a wire diameter which
is 1.18 times the side of the square.

Roy Lewallen, W7EL

wrote:
Anyone know how to use square rod in modelling programs?

I'm sure it's a small effect, but I'm interested in the *proper* way to
account for it vs. round rod.
. . .

thanks roy!