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[TowerTalk] Two antennas, same band, same tower.

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Subject: [TowerTalk] Two antennas, same band, same tower.
From: "K8RI on TowerTalk" <>
Date: Wed, 3 Jan 2007 18:58:40 -0500
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Back to antennas...

I have a Diamond Duoband vertical side mounted on the tower that is used mainly for 
near by repeaters and simplex to mobiles. I have a small antenna (not 
visible in the photo) at roughly the roof line for the local repeater and a 
second Diamond at the roof line on the far side of the shop (partially 
visible if you know where to look) I want to  add a second to the tower that 
will be used for digital in the 145 MHz range with a minimum of interaction.
There is heavily wooded low ridge line about a 100 yards to the West of my 
back yard which puts even the side mounted vertical well down into the trees 
when going West or SW.

I'm probably going to raise the current antenna about 10 feet, but that is 
about as close as I dare get to the TV antennas at roughly 90 feet. Those TV 
antennas have remote preamps and it takes traps to keep out the 2-meter 
signals which are between the high and low VHF bands.  I'd really like to 
put the second duobander right up on top of the mast, but with the lightning 
track record around here, antennas mounted up there would probably have a 
very high mortality rate.

I would guess mounting another on the opposite side of the tower would be a 
worst case with the most interaction. That leaves mounting the second one, 
either upside down (base to base) with the existing one, or side mount them 
with one immediately above the other. (top to base with no more than 2 or 3 
feet of separation).

Also note the stacked beams on both 144 and 440 bands at the top of the 

The reasoning behind this addition is a voice link on 440 to the NWS 
(usually takes the beams), remote station control as well as cross band 
receive on 440 and digital (both packet and as an Internet gateway routed to 
other ham gateways, the NWS and the local EOC)

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2 


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