[Antennas] Would vertical be better than yagi? Maybe...

[Charles Greene]

Karl,

I always thought the Yagi had a lower angle of radiation than a dipole when 
both antenna were at very low heights.  I modelled both antenna at 37 ft, 
about 11 meters, which is about 1/4 wavelength.  The ARRL antenna hand book 
shows differences between the Yagi and dipole on the second angle of 
radiation, but it is showing the angles for a height of 1 wavelength.  I am 
enclosing my Moxon and dipole files.  A quick glance doesn't show anything 
amiss; let me know if you can find any problems.  I am using EZNEC 3.0.39 
which I bought new about a year ago.

On the 1:4 Guanella balun, I wound three single core Guanella baluns with 
the two windings the same direction and noted a large difference in low 
frequency performance.  In fact, they have too much Lm, (magnetizing 
inductance) for the HF band, so I plan to rewind them all to give adequate 
input Zi on 160 meters but still have good HF performance through 10 
meters.  Not there yet.  I'm striving for a Lm of on the order of 110 uhy 
which is what I strive for on the two core baluns.  That will give a Zi of 
1243 ohms on 1.8 MHz.  If I can get this value Zi with flat performance 
through 10 meters, why not?  That means the balun will work better into a 
load of higher than 200 ohms than with an input impedance of the minimum 10 
times Zo (10 times 50 ohms).  Lm is the inductance measured across the 
input (50 ohm side), and Zi is the input impedance.

At 02:20 PM 6/12/2002 -0400, DJ5IL@aol.com wrote:

>W1CG@QSL.net wrote:
>
> > One big advantage of a Yagi compared to a dipole, is it's take off angle
> > is lower.  I modelled the field day Moxon Rectangle antenna in June 2000
> > QST for 40 meters with EZNEC, and also modelled a vertical and dipole
> > at the same height for comparison purposes.
>
>Chas,
>
>if mounted at the same height above the same ground, dipole and yagi
>definitely have the same optimum take-off angle and a difference would not be
>consistent with wave reflection theory. If you got other results from your
>simulation, you are either using and old EzNEC version (which used an
>inaccurate ground model for low heights) or you specified different ground
>charactersitics. Could you please email me me your .EZ files ? Which EzNEC
>version are you using ?
>
>P.S.: I will mail you more info very soon on my findings concerning the 1:4
>Guanella on one core ...
>
>73
>Karl, DJ5IL

73, Chas, W1CG

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