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OT: Vertical antenna ground systems

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Ken Kopp-3

OT: Vertical antenna ground systems

Of potential interest to those who use verticals with their Elecraft
rigs.

http://www.antennasbyn6lf.com/

73! Ken Kopp - K0PP
[hidden email]

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Alan Bloom

Re: OT: Vertical antenna ground systems

N6LF has done some wonderful experimental work on vertical antennas.

He found that a radial laid on the ground experiences a velocity factor
similar to coax cable. A quarter wavelength is only about 60% of its
free space value. If you make the radials a physical quarter wavelength
long, they are actually closer to a half-wave electrical length
(anti-resonant).

With 4 radials he actually got about a 3 dB improvement by making them
SHORTER!

For my next vertical I will definitely plan to tune the radials. I
think I'll try laying out a 1/2-wave dipole on the ground and then trim
it to resonance. Then cut all the radials to equal the length of one
half of the dipole.

Al N1AL

On Tue, 2008-11-04 at 19:10, Ken Kopp wrote:

> Of potential interest to those who use verticals with their Elecraft
> rigs.
>
> http://www.antennasbyn6lf.com/
>
>
> 73! Ken Kopp - K0PP
> [hidden email]
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
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hf4me

OT - L. B. Cebik (sk) website - Antenna related testing and design

L.B. Cebik(sk) was the technical editor for AntennaX magazine for many
years. He is now silent key but his website is now being hosted by the
magazine in his memory. There is a tremendous amount of information there.
He ahs also authored many books on antenna subjects including antenna
modeling that you will also find available on the website. This is a huge
information recourse. His books are great. His antenna testing and
analysis posted on the website is invaluable.

www.cebik.com

Take a look,
73, de Jim KG0KP

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George Badger

Re: OT: Vertical antenna ground systems

In reply to this post by Ken Kopp-3

Al
The worst length for a raised radial is a resonant quarter wave. Two together form a half wavelength. The problem is that the ground on one side of the "dipole" is not exactly the same as the ground on the other side so the "dipole" has a life of it's own and becomes a slightly off-center driven resonant dipole.
It will radiate some of your energy because of it's stored energy. Energy will be wasted because it will be radiated so close to ground.
The radials should be shorter or longer than a quarter wave so they do not form resonant dipoles. Bring the overall antenna system to resonance by adjusting the length of the monopole or adding appropriate reactance.
This is very well covered by Moxon [SK] in his book 'HF Antennas For All Locations' and elsewhere in the amateur press.
73
Good luck on your project.
George Badger W6TC

----- Original Message ----
From: Alan Bloom <[hidden email]>
To: Ken Kopp <[hidden email]>
Cc: [hidden email]
Sent: Wednesday, November 5, 2008 8:47:39 AM
Subject: Re: [Elecraft] OT: Vertical antenna ground systems

N6LF has done some wonderful experimental work on vertical antennas.

He found that a radial laid on the ground experiences a velocity factor
similar to coax cable. A quarter wavelength is only about 60% of its
free space value. If you make the radials a physical quarter wavelength
long, they are actually closer to a half-wave electrical length
(anti-resonant).

With 4 radials he actually got about a 3 dB improvement by making them
SHORTER!

For my next vertical I will definitely plan to tune the radials. I
think I'll try laying out a 1/2-wave dipole on the ground and then trim
it to resonance. Then cut all the radials to equal the length of one
half of the dipole.

Al N1AL

On Tue, 2008-11-04 at 19:10, Ken Kopp wrote:

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Don Wilhelm-4

Re: OT: Vertical antenna ground systems

In reply to this post by Alan Bloom

Alan,

LB Cebik and UN4UN (Low Band DXing) had some information on using tuned
radials - this is a situation that is covered under the topic of 'raised
radials'. The tuning technique is to tune each radial with the vertical
monopole separately - tune for reactance (X) = zero which is the
resonant condition without respect to the actual SWR or resistance
part. Tune each radial in turn (one at a time), and when all have been
tuned, connect them all together to form the 'ground plane'. After that
resonance tuning is complete, one can design a matching network to match
the resistive portion of the feedpoint to the feedline characteristic
impedance for best power transfer.

The conditions found by someone else in his particular situation may or
may not be applicable to the situation that your antenna exists in.

73,
Don W3FPR

Alan Bloom wrote:

> N6LF has done some wonderful experimental work on vertical antennas.
>
> He found that a radial laid on the ground experiences a velocity factor
> similar to coax cable. A quarter wavelength is only about 60% of its
> free space value. If you make the radials a physical quarter wavelength
> long, they are actually closer to a half-wave electrical length
> (anti-resonant).
>
> With 4 radials he actually got about a 3 dB improvement by making them
> SHORTER!
>
> For my next vertical I will definitely plan to tune the radials. I
> think I'll try laying out a 1/2-wave dipole on the ground and then trim
> it to resonance. Then cut all the radials to equal the length of one
> half of the dipole.
>
> Al N1AL
>
>
> On Tue, 2008-11-04 at 19:10, Ken Kopp wrote:
>
>> Of potential interest to those who use verticals with their Elecraft
>> rigs.
>>
>> http://www.antennasbyn6lf.com/
>>
>>
>> 73! Ken Kopp - K0PP
>> [hidden email]
>>
>> _______________________________________________
>> Elecraft mailing list
>> Post to: [hidden email]
>> You must be a subscriber to post to the list.
>> Subscriber Info (Addr. Change, sub, unsub etc.):
>> http://mailman.qth.net/mailman/listinfo/elecraft
>>
>> Help: http://mailman.qth.net/subscribers.htm
>> Elecraft web page: http://www.elecraft.com
>>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
> Help: http://mailman.qth.net/subscribers.htm
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Jim Brown-10

Re: OT: Vertical antenna ground systems

In reply to this post by George Badger

On Wed, 5 Nov 2008 18:39:03 -0800 (PST), George Badger wrote:

>The worst length for a raised radial is a resonant quarter wave.

Rudy, N6LF, recently presented some excellent NEW work on this topic
at Pacificon. A Power Point is on his website. It's worth chasing
down. Google on N6LF to find it.

73,

Jim K9YC

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David Cutter

Re: OT: Vertical antenna ground systems

Ralph Holland VK1BRH did a lot of very similar work and I think came to
similar conclusions.

David
G3UNA

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: "Elecraft List" <[hidden email]>
Sent: Thursday, November 06, 2008 3:23 PM
Subject: Re: [Elecraft] OT: Vertical antenna ground systems

> On Wed, 5 Nov 2008 18:39:03 -0800 (PST), George Badger wrote:
>
>>The worst length for a raised radial is a resonant quarter wave.
>
> Rudy, N6LF, recently presented some excellent NEW work on this topic
> at Pacificon. A Power Point is on his website. It's worth chasing
> down. Google on N6LF to find it.
>
> 73,
>
> Jim K9YC
>
>
>
> _______________________________________________
> Elecraft mailing list
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> You must be a subscriber to post to the list.
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