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OT - Interesting Accident with Homebrew Vertical

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Bob & Debbie Fish

OT - Interesting Accident with Homebrew Vertical

This is slightly off topic but I was using my K3, so it is close. I was
trying to set up a 2 element Vertical array in the back yard today
(actually for the last couple of days). A couple of 17 foot aluminum
tubing elements spaced 1/4 wavelength apart. With the bottoms of the
verticals about 6 feet high so I could run elevated radials to the top
of the surrounding back yard fence. (My wife loves the new view out the
back window, but, I digress). I could not get the verticals to play with
each other, I think the elevated radials were detuning each other or
something. So I gave up and decided to take down one vertical and just
run a single regular vertical with elevated radials.After I set up the
single vertical I went in the house and found the K3 had come alive with
lots of signals on the band and even some DX. I found a pileup working a
gent in Senegal on the CW part of the band and after ten minutes of
trying I worked him. So I was pretty happy with my project. I just went
out to put a plastic bag over the feed point because I haven't
waterproofed it yet and don't moisture in the open coax end. I noticed
that I had hooked up the shield of the coax to the vertical element and
the center conductor to the radials. (I was experimenting with running
180 deg out of phase for end fire and forgot to change it back). I am
not sure what that proves except that he radials really are half the
antenna. Working Africa from here on the west coast with only 100 watts
is pretty rare these days, so the backwards hookup is obviously working.

I guess it makes sense that it shouldn't matter. What do you guys think?

Bob K6GGO

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Don Wilhelm-4

Re: OT - Interesting Accident with Homebrew Vertical

Bob,

Indeed elevated radials *are* a part of the antenna (actually radials in
the ground are too). Elevated radials must be tuned (while buried
radials do not need to be). To do that properly, connect each one - one
at a time - and resonate it with the vertical element. When all have
been tuned, then they can be connected together.
To cancel the horizontal radiation component, the radials should be
oriented in opposing directions - any pair should be in a straight
line. 4 radials arranged 90 degrees apart is normally sufficient, and
in a pinch, 2 placed 180 degrees apart are sufficient.

It matters not whether the vertical part is fed from the center
conductor or the shield. The currents on the inside of the coax are
balanced (equal and opposite currents). The "magic" is to keep the
current off the outside of the coax shield, and that is what common mode
chokes (current baluns) should accomplish.

73,
Don W3FPR

Robert Fish wrote:

> I noticed
> that I had hooked up the shield of the coax to the vertical element and
> the center conductor to the radials. (I was experimenting with running
> 180 deg out of phase for end fire and forgot to change it back). I am
> not sure what that proves except that he radials really are half the
> antenna. Working Africa from here on the west coast with only 100 watts
> is pretty rare these days, so the backwards hookup is obviously working.
>
> I guess it makes sense that it shouldn't matter. What do you guys think?
>
>

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Steve Ellington

Re: OT - Interesting Accident with Homebrew Vertical

I think the original question was.....Can you feed the vertical section with
the braid and radials with center conductor?
I guess technically you could since neither one is grounded. It's weird to
think about.
Also I'm not too sure about all that "radial tuning" and canceling of
horizontal radiation if the radial system is only a few feet from the dirt.
It's interesting to think about how radiation is "canceled". Where's it go?
Think I'll go to bed and dream about this. 73
Steve
N4LQ
----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Robert Fish" <[hidden email]>
Cc: <[hidden email]>
Sent: Wednesday, February 03, 2010 11:06 PM
Subject: Re: [Elecraft] OT - Interesting Accident with Homebrew Vertical

> Bob,
>
> Indeed elevated radials *are* a part of the antenna (actually radials in
> the ground are too). Elevated radials must be tuned (while buried
> radials do not need to be). To do that properly, connect each one - one
> at a time - and resonate it with the vertical element. When all have
> been tuned, then they can be connected together.
> To cancel the horizontal radiation component, the radials should be
> oriented in opposing directions - any pair should be in a straight
> line. 4 radials arranged 90 degrees apart is normally sufficient, and
> in a pinch, 2 placed 180 degrees apart are sufficient.
>
> It matters not whether the vertical part is fed from the center
> conductor or the shield. The currents on the inside of the coax are
> balanced (equal and opposite currents). The "magic" is to keep the
> current off the outside of the coax shield, and that is what common mode
> chokes (current baluns) should accomplish.
>
> 73,
> Don W3FPR
>
> Robert Fish wrote:
>> I noticed
>> that I had hooked up the shield of the coax to the vertical element and
>> the center conductor to the radials. (I was experimenting with running
>> 180 deg out of phase for end fire and forgot to change it back). I am
>> not sure what that proves except that he radials really are half the
>> antenna. Working Africa from here on the west coast with only 100 watts
>> is pretty rare these days, so the backwards hookup is obviously working.
>>
>> I guess it makes sense that it shouldn't matter. What do you guys think?
>>
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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> Please help support this email list: http://www.qsl.net/donate.html

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14:35:00

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Dunc Carter - W5DC

Re: OT - Interesting Accident with Homebrew Vertical

It probably depends on how low the impedance of the radials and of the
vertical section are compared to the impedance of the outside of the coax.

Dunc, W5DC

Steve Ellington wrote:

> I think the original question was.....Can you feed the vertical section with
> the braid and radials with center conductor?
> I guess technically you could since neither one is grounded. It's weird to
> think about.
> Also I'm not too sure about all that "radial tuning" and canceling of
> horizontal radiation if the radial system is only a few feet from the dirt.
> It's interesting to think about how radiation is "canceled". Where's it go?
> Think I'll go to bed and dream about this. 73
> Steve
> N4LQ
> ----- Original Message -----
> From: "Don Wilhelm" <[hidden email]>
> To: "Robert Fish" <[hidden email]>
> Cc: <[hidden email]>
> Sent: Wednesday, February 03, 2010 11:06 PM
> Subject: Re: [Elecraft] OT - Interesting Accident with Homebrew Vertical
>
>
>
>> Bob,
>>
>> Indeed elevated radials *are* a part of the antenna (actually radials in
>> the ground are too). Elevated radials must be tuned (while buried
>> radials do not need to be). To do that properly, connect each one - one
>> at a time - and resonate it with the vertical element. When all have
>> been tuned, then they can be connected together.
>> To cancel the horizontal radiation component, the radials should be
>> oriented in opposing directions - any pair should be in a straight
>> line. 4 radials arranged 90 degrees apart is normally sufficient, and
>> in a pinch, 2 placed 180 degrees apart are sufficient.
>>
>> It matters not whether the vertical part is fed from the center
>> conductor or the shield. The currents on the inside of the coax are
>> balanced (equal and opposite currents). The "magic" is to keep the
>> current off the outside of the coax shield, and that is what common mode
>> chokes (current baluns) should accomplish.
>>
>> 73,
>> Don W3FPR
>>
>> Robert Fish wrote:
>>
>>> I noticed
>>> that I had hooked up the shield of the coax to the vertical element and
>>> the center conductor to the radials. (I was experimenting with running
>>> 180 deg out of phase for end fire and forgot to change it back). I am
>>> not sure what that proves except that he radials really are half the
>>> antenna. Working Africa from here on the west coast with only 100 watts
>>> is pretty rare these days, so the backwards hookup is obviously working.
>>>
>>> I guess it makes sense that it shouldn't matter. What do you guys think?
>>>
>>>
>>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
>
> --------------------------------------------------------------------------------
>
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.733 / Virus Database: 271.1.1/2666 - Release Date: 02/03/10
> 14:35:00
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>
>

Bill W4ZV

Re: OT - Interesting Accident with Homebrew Vertical

In reply to this post by Bob & Debbie Fish

N4KG used an interesting variation of this idea to feed a **grounded** tower on 160. He made four elevated 1/4 wave radials, attached the coax center conductor to the radials and the shield to the tower at the same point (up from the base several feet). If I recall this was in previous editions of the ARRL Antenna Handbook but I'm not sure it's in the latest edition.

73, Bill

Bill W4ZV

Re: OT - Interesting Accident with Homebrew Vertical

Bill W4ZV wrote

N4KG used an interesting variation of this idea to feed a **grounded** tower on 160. He made four elevated 1/4 wave radials, attached the coax center conductor to the radials and the shield to the tower at the same point (up from the base several feet). If I recall this was in previous editions of the ARRL Antenna Handbook but I'm not sure it's in the latest edition.

See Figure 28 on page 6-16 (Low Frequency Antennas chapter) of 20th edition. In newer editions you can probably find it by searching the index for N4KG.

73, Bill

Don Wilhelm-4

Re: OT - Interesting Accident with Homebrew Vertical

In reply to this post by Steve Ellington

Steve,

Elevated radials are not the same as buried radials - while related,
they are not the same. Elevated radials must be resonant, but in-ground
radials are untuned - those simply make the earth a better ground screen.

If the desire is for the antenna to be resonant (so it is easily fed
with coax), one must tune it. We are normally using 1/4 wave radiator
and 1/4 wave radials, but they can vary slightly from that exact length
and cause no problem We want the whole thing to be resonant, and that
can happen with a slightly long vertical section and slightly shorter
radials (or vice-versa) - think about it as a dipole fed slightly off
center, the feedpoint impedance changes a bit, the the dipole can still
be resonant.

You can tune the vertical element, or you can tune the radials. I
prefer to tune the radials rather than bringing the vertical element
down for pruning. Yes, there will be ground effects, and the easiest
way to do it is to cut the radials long and trim as required - that
compensates for any effects of ground and surrounding objects.
AND, if you want equal currents on the radials, each one must be tuned
to the same frequency (same electrical length), so tune each one in turn
with the vertical element, then connect them together at the feedpoint
when that has been finished. See ON4UN's Low-Band DXing Chapter 9
section 2.2.7 for details on this technique (the theory and discussion
is in section 2.2.6).

As far as cancellation of the radiation from the radials, yes, that will
happen if they are oriented in pairs 180 degrees apart. I refer you to
the writings of LB Cebik and others for verification. It does happen in
theory and modeling - how close it is achieved in practice is another
question.

73,
Don W3FPR

Steve Ellington wrote:

Don Wilhelm-4

Re: OT - Interesting Accident with Homebrew Vertical

In reply to this post by Bill W4ZV

In the 19th edition, it is figure 22 on page 6-14.

73,
Don W3FPR

Bill W4ZV wrote:

> Bill W4ZV wrote:
>
>> N4KG used an interesting variation of this idea to feed a **grounded**
>> tower on 160. He made four elevated 1/4 wave radials, attached the coax
>> center conductor to the radials and the shield to the tower at the same
>> point (up from the base several feet). If I recall this was in previous
>> editions of the ARRL Antenna Handbook but I'm not sure it's in the latest
>> edition.
>>
>>
>
> See Figure 28 on page 6-16 (Low Frequency Antennas chapter) of 20th edition.
> In newer editions you can probably find it by searching the index for N4KG.
>
> 73, Bill
>
>
>

Jim Dunstan

Re: OT - Interesting Accident with Homebrew Vertical

In reply to this post by Don Wilhelm-4

At 11:06 PM 2/3/2010 -0500, you wrote:

Hi,

Just as a side note .... I have used verticals with ground plane radials
... in pairs (4 radials work fb) ... to eliminate the horizontal radiation
component. However an interesting version is a vertical with only 1 radial
... in other words an "L" antenna vs the more common inverted "L" which is
usually worked against ground. I have used such an "L" antenna with the
base about 15 ft off the ground ... the vertical portion apporx 26ft of
self supporting (more or less) aluminium and the horizontal portion about
30 ft of copper wire. I fed the antenna with ladder line to a balanced
antenna tuner. It has an almost omni directional pattern with both hi and
low angle radiation. It is what you might call the middle of the road
antenna ... e.g. general purpose. Very efficient on all bands and works
well for local contacts with very good propagation at a distance.

The antenna used to be featured in older antenna handbooks .... but
disappeared as coax cable feed started to become the norm.

Jim, VE3CI

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