I just started playing with EZNEC and am modeling an Inverted V for 20
meters with the lowest SWR at 14.1mhz up about 25 feet. Angle will be
90 degrees. My figures show that each leg to be a little over 17 feet
long. Doesn't seem correct to me. Could someone plug my figures in and
tell me if I'm right or wrong. I would appreciate it.

Thanks

On Wed, 18 Aug 2004 11:44:57 -0500, JerryB wrote:

My figures show that each leg to be a little over 17 feet
long. Doesn't seem correct to me.

Hi Jerry,

Trust your tool, or give a reason why it doesn't seem correct.

73's
Richard Clark, KB7QHC

Thanks for the reply. I had seen formulas for dipoles using 468/FMhz
and the V's were always 2 to 5% shorter, which would make the V about
16 foot per leg. But I guess that's not taking height and angle into
consideration. I'm learing so guess I have more to do. Thanks again.

Jerry





On Wed, 18 Aug 2004 17:55:30 GMT, Richard Clark
wrote:

On Wed, 18 Aug 2004 11:44:57 -0500, JerryB wrote:

My figures show that each leg to be a little over 17 feet
long. Doesn't seem correct to me.

Hi Jerry,

Trust your tool, or give a reason why it doesn't seem correct.

73's
Richard Clark, KB7QHC

On Wed, 18 Aug 2004 13:52:43 -0500, JerryB wrote:

Thanks for the reply. I had seen formulas for dipoles using 468/FMhz
and the V's were always 2 to 5% shorter, which would make the V about
16 foot per leg. But I guess that's not taking height and angle into
consideration. I'm learing so guess I have more to do. Thanks again.

Hi Jerry,

At best, such formulas are a starting point, and one should always cut
the wire LONGER than any solution offers.. This is so that you can
trim it to accommodate local variations in geology, topography,
interfering trees and houses and the world in general.

Modeling programs attempt to anticipate a myriad of complications,
such as your height and angle variables to aid in construction. Also,
modeling programs attempt to portray the consequences of building your
antenna by providing matching information and launch characteristics
so that you can vary elements and observe the impact of your actions
before you start building.

This is all relative of course. Your back yard may not conform to the
model's expectations, and you would then experience a divergence from
your own expectations of performance. However, even in this regard
you have a basis of comparison. You can vary the model's settings
(generally this reflects a poor choice of ground type or wire size or
its insulation) to conform to your reality, and then alter the model
to what your desired characteristics and be relatively assured that
changing your physical model in a similar manner will result in
greater success.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Wed, 18 Aug 2004 13:52:43 -0500, JerryB wrote:

Thanks for the reply. I had seen formulas for dipoles using 468/FMhz
and the V's were always 2 to 5% shorter, which would make the V about
16 foot per leg. But I guess that's not taking height and angle into
consideration. I'm learing so guess I have more to do. Thanks again.

Hi Jerry,

At best, such formulas are a starting point,

468/f is said to have been derived from a low dipole for 40m, strung in
the back-alley of the old ARRL HQ building. Anywhere else, expect
different results.

and one should always cut
the wire LONGER than any solution offers.. This is so that you can
trim it to accommodate local variations

Good advice.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

A very rare, welcomed, combination of events has occurred.

First we have a sensible, concise, well-presented enquiry about
inverted-V's.

And secondly we have a response from Richard (Clark) which combines both his
advanced (never doubted) technical knowledge and his ability (but long
awaited) to express himself in the logical, unambiguous, easy-to-understand
English language.

Makes a change from the deliberately confusing, psychologicially mixed-up
stuff we are accustomed to. Keep up the good work.

But may I say I have learned a lot over the years from your own
how-not-to-do-it mode of expressing yourself.

Richard, please forgive me for being so forthright in public. I'm on
Valencia red this evening. I'm sure you will understand.

Incidentally, I think the English and American languages, after a
generation's lapse, are coming back closer together again. You get rid of
Bush and we'll get rid of Blair.
---
Yours, Punchinello, G4FGQ.

There's a small program named INV_VEE available from website below.

It will tell you immediately all you wish to know about interactions between
wire lengths, height above ground, apex-angle between 0 and 180 degrees,
wire-size, feeder loss, SWR, radiating efficiency, etc., of any inverted-V
at any fequency.

It won't tell you much about its radiation pattern but that's already a
simple, well known property of the popular inverted-V. For practical
purposes, at ordinary apex angles, it is omni-directional and fairly
low-angle as EZNEC is designed to show you.

Download INV_VEE in a few seconds and run immediately. Good DX-ing with it.

Free to USA citizens.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........