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 DOUBLE EXTENDED ZEPP 
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Post DOUBLE EXTENDED ZEPP
Would it be possible to configure a home brew Double extended zepp (single band) in a inverted V fashion?

Would the element dimensions need adjustment & what's the best inverted degree for low angle radiation pattern that would not interact with the feeder.

Would it be more effective to consider a vertical antenna ?

Thx

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Wed Nov 22, 2017 12:52 pm
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 DOUBLE EXTENDED ZEPP 
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Post Re: DOUBLE EXTENDED ZEPP
What band? Inveriably on the lower bands it's going to be an NVIS antenna no matter what you do to the ends. What you could do is something similar to what I do with my doublet and that is to turn it into a Marconi Tee by stapping the feeders at the bottom, I use a relay box and an SG230 to match the strapped feeders.

That gives me about an S point or two on the longer range signals, or if I want to work the closer in stuff I just feed it as a doublet.

From memory when I modelled an inverted Vee the NIVS actually increased, I'm at work at the moment but I'll try and find the info when I get home.

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Wed Nov 22, 2017 2:26 pm
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 DOUBLE EXTENDED ZEPP 
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G4LNA wrote:
What band? Inveriably on the lower bands it's going to be an NVIS antenna no matter what you do to the ends. What you could do is something similar to what I do with my doublet and that is to turn it into a Marconi Tee by stapping the feeders at the bottom, I use a relay box and an SG230 to match the strapped feeders.

That gives me about an S point or two on the longer range signals, or if I want to work the closer in stuff I just feed it as a doublet.

From memory when I modelled an inverted Vee the NIVS actually increased, I'm at work at the moment but I'll try and find the info when I get home.


Thank-you Paul,
20m band
THX

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Wed Nov 22, 2017 2:37 pm
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 DOUBLE EXTENDED ZEPP 
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How high above the ground is it? This will have an affect on the radiation pattern.

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Wed Nov 22, 2017 4:01 pm
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 DOUBLE EXTENDED ZEPP 
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G4LNA wrote:
How high above the ground is it? This will have an affect on the radiation pattern.


47ft
Thx

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Wed Nov 22, 2017 4:12 pm
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 DOUBLE EXTENDED ZEPP 
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Post Re: DOUBLE EXTENDED ZEPP
Wow, that's a good height.

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Wed Nov 22, 2017 4:27 pm
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 DOUBLE EXTENDED ZEPP 
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Post Re: DOUBLE EXTENDED ZEPP
OK, I've had a play around with this antenna and I've come to the conclusion that it isn't the best antenna for 20M. The optimum height is about 30 feet for 20M when it's horizontal, you do get a large lobe broadside to the antenna at that height but it is very narrow, any higher and the main lobe starts going straight up when you reach 47 feet in height. Bending the ends down into inverted Vee reduces the side lobes and just increases the main lob, as I suspected and it ties in with what others have found on line.

The Double Zepp is really intended as a low band antenna where you want NVIS, in other words the lobe going straight up in the sky. It is a similar length to my doublet that I use on all bands and that works really well on all bands up to 30M, after that I often strap the feeders and use it as a Marconi Tee. I can switch between the two, so I select either the vertical or the horizontal whichever gives the best signal.

You might be better off with a 30 foot vertical against a radial system for 20M.

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Wed Nov 22, 2017 5:09 pm
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 DOUBLE EXTENDED ZEPP 
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Post Re: DOUBLE EXTENDED ZEPP
I'd say that just about anything at 47 feet will outperform any vertical.

I'd just use a doublet, or even a trap dipole, so that the 'current' part (which does the radiating) is up high.

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Wed Nov 22, 2017 5:42 pm
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 DOUBLE EXTENDED ZEPP 
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The project was to try & maintain the dbi gain of the double extended zepp & direct it in a low angle radiation pattern.The thought of using a ground reflector system had also been in the equation,Thanks to Paul & Chris for advise & comments.

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Wed Nov 22, 2017 6:04 pm
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 DOUBLE EXTENDED ZEPP 
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Post Re: DOUBLE EXTENDED ZEPP
2E1GSN wrote:
The project was to try & maintain the dbi gain of the double extended zepp & direct it in a low angle radiation pattern.The thought of using a ground reflector system had also been in the equation,Thanks to Paul & Chris for advise & comments.


Ground reflectors are an 'NVIS thing' (you're in my territory here :) ). You are in effect making a 2-element Yagi pointing straight up.

A good single-band balanced dipole or doublet will give deep joy, oh yes.

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Wed Nov 22, 2017 6:12 pm
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 DOUBLE EXTENDED ZEPP 
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Post Re: DOUBLE EXTENDED ZEPP
47 feet up.

Image

30 feet up.

Image

As you see, the higher you go, the more the lobe grows towards the sky. And see how narrow the lobe is at 30 feet, it will knock spots off a vertical, just hope it's in the right direction, unless you can turn your garden around, now there's a project :thumbsup:

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Wed Nov 22, 2017 7:09 pm
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 DOUBLE EXTENDED ZEPP 
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Post Re: DOUBLE EXTENDED ZEPP
Very informative Paul & food for thought,Thanks for all your effort.

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Wed Nov 22, 2017 7:23 pm
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 DOUBLE EXTENDED ZEPP 
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Post Re: DOUBLE EXTENDED ZEPP
I mentioned earlier about a 30 foot vertical which is nearly a full wave on 20M, this is what it looks like, notice the very low radiation angle of about 20ᵒ.

Image

It is a very high impedance at the bottom, so the simple LC network will be sufficient to match it to 50 Ohms.

Image

You will need a few radials, but they only need be very short ones and probably only half a dozen.

I meant to add, the radiation angle of the Double Zepp is about 60ᵒ, so some signals will be stronger on the vertical and some will be stronger on the Zepp depending on where the signal is coming down from above ;)

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Wed Nov 22, 2017 7:30 pm
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 DOUBLE EXTENDED ZEPP 
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Post Re: DOUBLE EXTENDED ZEPP
I remember Steve demonstrating to me (to put it diplomatically) once, that - no matter how 'good' and 'neat' the vertical's graph looks for low angle compared to a dipole - that the dipole will still always have gain over the vertical, no matter what low angle you choose.

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Wed Nov 22, 2017 8:11 pm
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 DOUBLE EXTENDED ZEPP 
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Post Re: DOUBLE EXTENDED ZEPP
Don't forget Chris, in some directions the long dipole, extended zepp whatever you want to call them, has up to -11dbi in some directions against 0dbi on the vertical, so the vertical wins in that situation, you have just got to be lucky the gain from the long dipole is in the direction you want.

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Wed Nov 22, 2017 8:26 pm
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