I'm putting up a Diamond V-2000 (Omni directional 6m/2m/440) on my tower
with a side arm. I've been told to expect some degradation in the 'shadow'
direction. Just how bad will this be in dB? Any affect on other directions?

--
Bob D. ND9B

On Sun, 13 May 2007 12:45:43 -0400, "Bob D."
wrote:

I'm putting up a Diamond V-2000 (Omni directional 6m/2m/440) on my tower
with a side arm. I've been told to expect some degradation in the 'shadow'
direction. Just how bad will this be in dB? Any affect on other directions?

Hi Bob,

You would have to work extremely hard to optimize that shadow. Any
less work will hardly be noticed. (Look at any of a number of towers
supporting UHF antennas that are generally omni-directional.)

Keep the antenna far enough away so as to not detune it, however.

73's
Richard Clark, KB7QHC

"Bob D." wrote in message
m...
I'm putting up a Diamond V-2000 (Omni directional 6m/2m/440) on my tower
with a side arm. I've been told to expect some degradation in the 'shadow'
direction. Just how bad will this be in dB? Any affect on other
directions?

--
Bob D. ND9B

You can go here to find a program that will plot the patern.

http://www.repeater-builder.com/ante...sys-index.html

Here is the name of it.

ANTPLOT - A Side-Tower Mounted Antenna Pattern Prediction Program

Depending on how far from the tower you mount the antenna you can get from a
few db to very deep nulls in many directions.

Hi Bob

I modeled a commercial install some years ago on 148MHz (pagers) that
ended up with maybe 3-4 nulls between 6 and 9dB on the shadow side. This
was also born out by a site/coverage test.

As it turns out the antenna mounting designers hit this as a pure fluke
or if you like plain old bad luck! Moving the antenna in or out maybe
10" yielded ripples less than 3dB. The reason we were even looking at
the pattern was that the coverage had gaps in the prediction off the
back of the mast. The modeling (nulls) actually matched the places where
the signal was low.

You can of course place an antenna for best gain off the mast as a
reflector of sorts. The URL below is an extended double 5/8 ZEPP with a
center hairpin feed that I more or less optimized for that.

http://pages.suddenlink.net/vk2yqa/f...0patter n.gif

F/B is about 6dB

Cheers Bob VK2YQA

Bob D. wrote:
I'm putting up a Diamond V-2000 (Omni directional 6m/2m/440) on my tower
with a side arm. I've been told to expect some degradation in the 'shadow'
direction. Just how bad will this be in dB? Any affect on other directions?