If I join some extra wire to the ends of the G5RV half size and bring them
down towards the bottom of the 300 Ohm slotted feeder to make a triangle
shape, kept vertical. Would this radiate ok or would it be a waist of time?

Is there a modelling program I could buy for HF antennas?

Thanks

I think its called a modelling program? I was told a long time ago that's
there is a program where you can input the shape and size of an antenna and
it will predict how well it would work.

Is there such a program and how simple is it to use?

At the moment I'm trying all different setups to try and get the best I can,
because of the space and the neighbours.

Many thanks



"Barrett" wrote in message
...
If I join some extra wire to the ends of the G5RV half size and bring them
down towards the bottom of the 300 Ohm slotted feeder to make a triangle
shape, kept vertical. Would this radiate ok or would it be a waist of
time?

Is there a modelling program I could buy for HF antennas?

Thanks

Barrett wrote:
I think its called a modelling program? I was told a long time ago that's
there is a program where you can input the shape and size of an antenna and
it will predict how well it would work.

Is there such a program and how simple is it to use?

There are a couple programs out there that are free for use. The demo
program of EZ-nec, and 4Nec2.

What I would suggest is getting a copy of EZNEC. Then go through the
tutorials.

As for easy or difficult, you sound like a real new guy - that's okay,
no one was born knowing all this stuff, and we all have to start
somewhere. The important thing is to start. It will probably be a little
daunting for a while.

How familiar are you with the basic concepts? Then we'll know where to
start. There are some good web references out there, depending on where
you want to start.

- 73 de Mike N3LI -

I've just downloaded EZNEC v. 5.0 demo.
I'm only just starting to learn the basic concepts from the beginning.

Thanks

"Michael Coslo" wrote in message
...
Barrett wrote:
I think its called a modelling program? I was told a long time ago that's
there is a program where you can input the shape and size of an antenna
and it will predict how well it would work.

Is there such a program and how simple is it to use?

There are a couple programs out there that are free for use. The demo
program of EZ-nec, and 4Nec2.

What I would suggest is getting a copy of EZNEC. Then go through the
tutorials.

As for easy or difficult, you sound like a real new guy - that's okay, no
one was born knowing all this stuff, and we all have to start somewhere.
The important thing is to start. It will probably be a little daunting for
a while.

How familiar are you with the basic concepts? Then we'll know where to
start. There are some good web references out there, depending on where
you want to start.

- 73 de Mike N3LI -

"Barrett" wrote in
:

I've just downloaded EZNEC v. 5.0 demo.
I'm only just starting to learn the basic concepts from the beginning.


Okay Barrett,

One of the basic concepts that is helpful is the "wavelength".

The speed of an RF signal in free space is the speed of light.

Imagine a pure RF sine wave. Starting at zero, the sine will increase to
maximum, then turn around, cross zero again, then go to the other
maximum, and then return to zero. The distance traveled while that
happens is the wavelength. Pretty simple, that, but all the other parts
are related to it. A lower frequency travels further before returning
than a higher one does.

Now in order to have an antenna that will cooperate with our
transceivers, it needs a particular impedence, or near to it. What most
equipment uses is 50 ohms impedence. Some equipment use 75 ohms, but
nothing we're interested in Amateur radio.

So if you are designing a single band antenna that uses coax, you'll want
to hit around that value of impedence.

There is a relationship between the length of the antenna and the
wavelength. In the case of a typical antenna for amateur radio use, the
dipole, you'll end up with around a half wavelength antenna, 1/4
wavelength on each side to get near that impedence. Other antennas may
use more complicated ways of coming up with the proper impedence.

These are generalizations. There are some other aspects, such as changes
in the speed of the RF through cables and insulated wires being different
than in free space, but what I gave you so far is pretty much the basic
basics.

- 73 de Mike N3LI -

Barrett wrote:
If I join some extra wire to the ends of the G5RV half size and bring them
down towards the bottom of the 300 Ohm slotted feeder to make a triangle
shape, kept vertical. Would this radiate ok or would it be a waist of time?

The 300 ohm line is a series-section transformer that
works with the G5RVjr antenna feedpoint impedances
encountered on 40m, 20m, 10m, and 6m. If you change
the antenna, you change the antenna feedpoint impedance.
It would be a virtually impossible coincidence if the
same series-matching transformer worked well on a
different antenna.

Is there a modelling program I could buy for HF antennas?

EZNEC is available from www.eznec.com. Before buying,
you can test drive the free demo version which has
a 20 segment limit. EZNEC is a very time efficient
way to learn about antennas.
--
73, Cecil http://www.w5dxp.com