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

[Charles Greene]

Karl and All,

I'm sorry I have to disagree with you Karl.  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. A Moxon Rectangle is a two element beam with the ends 
folded toward the center.  Results:

         Vertical angle
         of maximum radiation           Gain

1/4 Vertical         22 deg            -.59 dBi

40 meter dipole      62 deg            6.61 dBi
at  37 ft.

Moxon Rectangle      45 deg            9.55 dBi
at 37 ft

The antenna is for 40 meters but a similar comparison can be made for 
higher frequencies.  Actual results may vary, but the advantage of the beam 
with respect to gain and take off angle is readily apparent.

For actual results, I have a G5RV at 30' and its gain is about the same as 
my Hustler 6BTV vertical on 20 on US stations but slightly better on 
DX.  The gain of the G5 is slightly greater on 40.  I don't have a 
comparison on the other bands except to state that they both work about the 
same.

73's

At 05:55 PM 6/11/2002 -0500, Karl Kanalz wrote:
>Actually, John, if you look at the elevation patterns ("take-off angle")
>of a Yagi antenna, you'll find that the take-off angle of a Yagi is the same
>as a dipole at the same height!  The major difference is that the Yagi has
>(usually) a front-to-back and front-to-side ratio that the dipole *doesn't*
>have,
>and that's why it produces "gain" over the dipole.
>
>Your particular "... lack of height..." is why your Yagi is not performing
>as
>expected.
>
>If you'll read the appropriate sections of the ARRL "Handbook" or the
>ARRL "Antenna Book", you'll begin to understand the importance of
>height above ground for *any* antenna, and how it affects the radiation
>pattern, the "take-off angle" and so on......
>
>Karl K - W8TIF
>McKinney, Texas
>
>-----Original Message-----
>From: John Geiger
>Sent: Tuesday, June 11, 2002 3:04 PM
>To: antennas@mailman.qth.net; dx-list@yahoogroups.com; dx@mailman.qth.net
>Subject: would vertical be better than yagi?
>
>I recently put up a 2 element triband yagi (full size
>tribander) but it is not up very high-maybe 25 feet or
>so.  The lack of height is noticable in performance.
>It does show gain towards Europe vs my dipole (G5RV
>type, also not up very high), and it also showed gain
>over the dipole when working VK9LO the other day.
>SOmetimes the yagi is a couple of S units better than
>the dipole towards Europe.  Most of this has been done
>on 20 meters.  Have not found enough stuff on 10 to
>compare yet.
>
>However, the past few days been trying to work BQ9P
>for #298, and the yagi doesn't show much gain at all
>over the dipole towards the far east-observe the same
>with Japan.  Did work DU3NXE on 20 cw this AM with the
>yagi, but he was about as loud on the dipole.
>
>THe way I understand it, the low height does not give
>me the low angle radiation lobes that the long haul DX
>often requires.  So my question is:  Given that I
>might not be able to get the Yagi much higher for some
>time (my yard is a nightmare of trees and power lines)
>would I be better off getting a vertical on the roof
>instead.  I know that verticals hear equally poor in
>all directions, but would it allow me to get the lower
>angle-long haul stuff.
>
>I would appreciate any comments, especially from those
>who have been in the same boat.
>
>73s John NE0P

73, Chas, W1CG