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Re: [Antennaware] 2-element delta loop array close to ground

To: "'Pete Smith'" <>, <>
Subject: Re: [Antennaware] 2-element delta loop array close to ground
From: "Stephen Kangas" <>
Date: Fri, 28 Nov 2008 10:56:43 -0800
List-post: <">>
This is one of the characteristics of the driven or single director Delta
Loop, an omni pattern.  However, that pattern is made up of a horizontally
polarized component that is directional perpendicular to the plane of the
loop and a vertical polarized component in-line with the plane of the loop
(you should see that in the modeling program if you have the option of
selecting a view of either/both polarizations).

The antenna should become more directional in each of the two polarizations
when adding more elements, ie narrowing the lobes and increasing F/B ratio.

Also, I recommend placing the apex down, which improves the pattern when the
antenna is that close to the ground.  Also, I have had good luck making a
"Super" Delta Loop, that uses ladder line placed into the middel of the side
opposite the apex that is quarter wave of the lower band and acts as a
"trap"  to turn the loop into a dual-bander while also increasing the gain
of the lower band (up to 9.4dbi.  However, this cannot be realistically
modeled in EZNEC, MMANA, and other similar low cost programs as the ladder
line trap requires a very high number of segments (need NEC PRO or better
program); using these programs throws way off the predictions of
impedance/resonance/swr, altho the patterns produced by MMANA are pretty
close.  If you want to build that antenna for 80/40, let me know and I'll
supply the final materials/dimensions I used.  Even this antenna needs to
have the apex up at least 30-35ft.  You'll need a 4:1 current balun for a
delta loop.

-----Original Message-----
[] On Behalf Of Pete Smith
Sent: Friday, November 28, 2008 6:56 AM
Subject: [Antennaware] 2-element delta loop array close to ground

I am modeling a 20M 2-element delta loop array with the apex up, 12-foot
spacing and the bottom about 35 feet above ground, fed at a lower corner,
using Multi-NEC and NEC2.  In driven/reflector configuration, it looks about
like what I'd expect - 6 dBi gain and 14-18 dB F/B.  But in the
driven/director configuration, there isn't much directivity at all,
regardless of frequency.

Does this square with others' experience, or am I messing something up in
the model?

73, Pete N4ZR
the World Contest Station Database is back...

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