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Antenna Idea




 
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WA4WAX
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« on: October 26, 2022, 09:40:53 PM »

This is for 20 meters.....a beam idea.  Small yard, HOA regs, etc.  Small budget.

Make two rectangular SCV antennas as per Cebik.  Using 14.200 MHz, I get 6.5 x 29 feet rectangles.  Erect two, with the bottom wire 9 or 10 feet above the ground. They should be parallel.  Space them 1/4 wave (A little over 16 feet).  Feed in the center of a vertical member.  Use a short section of 450 ohm balance line and a shunt variable immediately followed by a current balun. You will have to experiment wiht the length of 450.....should not be more than a couple of feet.  Set each rectangle to 50 + 0.  Make a phasing harness with RG-213 or LMR-400.  Use type N.  Connect both lines to an unbalanced L in a small box.  This will transform 25 ohms back up to 50 ohms.  Main direction of radiation should be broadside to the lagging rectangle. 

Thoughts from the group?  Anybody want to simulate the pattern?
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Pete, WA2CWA
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« Reply #1 on: October 27, 2022, 01:41:40 AM »

Why not just two parallel dipoles fed out of phase (Lazy H)?
For real cheap, a simple dipole will work.
Then there's the issue of rotation.
A flag pole vertical probably would look less obvious for the HOA police.
Then there's always the infamous "TAK antenna". Hams hang these from their balconies.
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Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
WA4WAX
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« Reply #2 on: October 27, 2022, 02:14:29 AM »

Pete:

The elements of a Lazy H are fed in phase.  What is more, it is a big honker.

The proposed antenna is not expected to be a world beater, but it is relatively small and cheap. 

It offers a low angle....something a dipole at the same height could never do.

One more thing: Swap the phasing lines to reverse direction.

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K9MB
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« Reply #3 on: October 27, 2022, 07:56:59 PM »

Just curious- Since you obviously are familiar with CEBIK’s work, why not build a shrunken quad a.l.a CEBIK?

14 feet on a side- 10 ft boom for 20 meters.
Probably can use 10’ pvc pipe for spreaders.

https://formufit.com/products/1-1-4-in-5-way-cross-furniture-grade-pvc-fitting-connector?variant=15069737732&currency=USD&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=CjwKCAjw2OiaBhBSEiwAh2ZSP9OjnZByLOq5D31dd9pCJ8uD5RJfrWweq6QVlDOpR1Uy66ghfXHoYxoCyFwQAvD_BwE

7.2dB gain.

http://www.antentop.org/w4rnl.001/quad3.html
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WA4WAX
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« Reply #4 on: October 28, 2022, 05:51:06 PM »

I am familiar.

It still needs a mast on 20 meters......30 feet or more.

My goal here is something that does not go too far in the vertical direction. Also, something that is stealthy and unobtrusive.

True, it cannot be rotated......but you can reverse direction by swapping the phasing lines.
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K9MB
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« Reply #5 on: October 29, 2022, 01:37:40 PM »

I am not sure why you are looking for a directional antenna if you do not wish to rotate it.

Why not run a rope between two supports that can suspend a vertical wire and then put a few 16-20 ft radials on tue ground and secure with lawn staples and mount your feed on a short pipe and run your coaxial cable on the surface using the same lawn staples. You can put a choke balun at the base if you like.
It will be close to 50 ohms with 12 radials and will give you an omnidirectional low angle antenna. Add fan elements for 15 and 10 meters.

If you do not want ground radials, raise the support 7 feet and add another rope at 7 feet to support a folded counterpoise tuned to 20 meters and an isolatiin transformer to raise efficiency by decoupling from the ground (See work by N6LF and K2AV).

https://www.ivarc.org.uk/uploads/1/2/3/8/12380834/rfgroundpaper.pdf

https://www.radioenthusiast.co.uk/news/radials-for-quarter-wave-verticals-an-overview/

https://www.nonstopsystems.com/radio/pdf-ant/article-antenna-elevated-radials.pdf

https://rudys.typepad.com/files/elevated-ground-systems-article-final-version.pdf

https://k2av.com/

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R. Fry SWL
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« Reply #6 on: October 30, 2022, 06:46:06 AM »

This is for 20 meters.....a beam idea.  Small yard, HOA regs, etc.  Small budget. ... Thoughts from the group?  Anybody want to simulate the pattern?

The antenna described below may be a possibility for you ...?


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KD6VXI
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« Reply #7 on: October 30, 2022, 12:23:10 PM »

He's trying to gt a low take off angle while having to hide it from an HOA.

Almost all thr ideas being presented don't pass the HOA problem.

I'd bet he's trying to hide it behind a house or other such structure.  Hen e the want and need for such a low mounting height.   Unless you load the heck out of a vertical, on 20, it's not going to be below 9 or 10 feet above ground level.

Antenna he's talki g about seems sound.  I'd ensure you will get what you want for take off, etc by modeling it with your ground, etc parameters as close as possible.

I mean, it's got to be decades better than a taktenna....?


--Shane
WP2ASS / ex KD6VXI
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WA4WAX
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« Reply #8 on: October 30, 2022, 01:53:51 PM »

I do not have an HOA problem.  I can put up pretty much what I want.  That will likely be an inverted L, later followed by an 8JK.

It is just an idea.  I am quite familiar with a 1/4 vertical with 4 elevated radials.....that is another Cebik topic.

You could space a pair of those verticals 90 degrees and phase them 90 degrees.  As I said, you could also do that with a pair of rectangles.

It would be interesting to see field simulations for both.

BTW, do not forget current baluns and static drains.

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KD6VXI
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« Reply #9 on: October 31, 2022, 06:41:39 AM »

"This is for 20 meters.....a beam idea.  Small yard, HOA regs, etc.".    From first post

"I do not have an HOA problem".    From last post


Sits back utterly confused.



--Shane
WP2ASS /ex KD6VXI
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ka1bwo
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« Reply #10 on: October 31, 2022, 10:42:32 AM »

"This is for 20 meters.....a beam idea.  Small yard, HOA regs, etc.".    From first post

"I do not have an HOA problem".    From last post


Sits back utterly confused.



--Shane
WP2ASS /ex KD6VXI
Shane, I seen this time and time again. Let them do their own analysis and show us the results for discussion.
Joe
Ka1bwo
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WA4WAX
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« Reply #11 on: October 31, 2022, 10:48:12 AM »

I do not have an HOA problem.

Some might, so I am throwing this out as an item of interest.

The rectangular loops could be placed in a back yard and folded down during the day.  After sundown, they could be folded up.

Someone on the board might want to simulate two rectangles space 90 degrees and phase 90 degrees, with two 4 radial verticals spaced and phased the same way.

Radials 9 feet up for the verticals.  Bottom wire 9 feet up for the rectangles.

BTW, the HOA crowd could take a similar approach with an end fed 8JK.  In the day time, tell the old buddy walking by that is a clothes line.  Run the poles up to about 20 feet after dark.

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WA4WAX
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« Reply #12 on: October 31, 2022, 10:58:56 AM »

Old biddy I meant to type.

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w4bfs
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« Reply #13 on: October 31, 2022, 11:08:57 AM »

nothing else is as misunderstood as altruism
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Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
K9MB
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« Reply #14 on: October 31, 2022, 04:58:37 PM »

nothing else is as misunderstood as altruism

I considered being an altruist, but could not see anything in it for me…😉😂
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w4bfs
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« Reply #15 on: November 01, 2022, 03:08:19 PM »

 Grin Grin Grin
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Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
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