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Re: [TowerTalk] Yagi gain vs rotary dipole.

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Yagi gain vs rotary dipole.
From: "Joe Subich, W4TV" <lists@subich.com>
Date: Tue, 25 Nov 2014 17:44:31 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>


## Ok, what are u saying here. Lets say a 20m dipole and a 3-el 20m
yagi.... both at 70 feet.At really low angles..say 0-10 deg.....
will the 3-el yagi have even more than 5.2 db of gain ?? Or put
another way... even though 70 feet = aprx 15 deg take off angle of
main lobe.... does the yagi exhibit more gain vs the dipole at angles
below 15 deg ?

A little work with EZNEC provides some answers ...

Using the model of a five element 20 meter yagi at 50 feet and a dipole
at 50 feet above *real* average ground ...

The dipole has a peak gain of 8.0 dBi at 21 degrees.

The 5 element Yagi shows 14.4 dBi at 18 degrees

 Angle     Dipole       Yagi
  2        -7.7        -0.1    dBi
  4        -1.8         5.7    dBi
  6         1.5         8.9    dBi
  8         3.7        11.0    dBi
 10         5.2        12.4    dBi
 12         6.3        13.4    dBi
 14         7.1        14.0    dBi
 16         7.6        14.3    dBi
 18         7.9        14.4    dBi
 20         8.0        14.3    dBi
 22         7.9        13.9    dBi
 24         7.6        13.4    dBi
 26         7.1        12.6    dBi
 28         6.4        11.6    dBi
 30         5.5        10.4    dBi

73,

  ... Joe, W4TV


On 2014-11-25 1:52 PM, Jim Thomson wrote:
Date: Mon, 24 Nov 2014 20:46:14 +0100
From: "Peter Voelpel" <dj7ww@t-online.de>
To: "'Towertalk'" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Yagi gain vs rotary dipole.

Hi Jim,

To get the same signal strength -4db compared to the 3el yagi on low angles
with your dipole that dipole must be mounted much, much higher then the yagi
and even higher with more elements on the yagi.

Tribanders at the same height as the 6 el monobander certainly will have
identical gain when the effective boom length is identical and enough
elements sitting on it.

I don?t build yagis for getting more gain above dipoles at high lobes, but
for low elevation angles and better receiving.


73
Peter

##  Ok, what are u saying here.  Lets say a 20m dipole and a  3-el 20m yagi.... 
both at 70 feet.
At really low angles..say 0-10 deg..... will the 3-el  yagi have even more than 
5.2 db of gain ??
Or put another way... even though 70 feet  = aprx 15 deg take off angle of main 
lobe.... does the
yagi exhibit more gain vs the dipole at angles below 15 deg ?

##  anytime I have done yagi to dipole tests in the past..the difference was 
astounding.  I always
assumed it was cause the dipole was fixed...not rotatable...  and not quite 
broadside to the station.

Jim

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