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Re: [TowerTalk] Field Day Antennas - Multiband Vee-Beam?

To: "Tower and HF antenna construction topics." <>
Subject: Re: [TowerTalk] Field Day Antennas - Multiband Vee-Beam?
From: David Gilbert <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Fri, 23 Apr 2010 11:20:20 -0700
List-post: <">>
Hi, Steve.

I've done EZNEC analyses on antennas like that in the past and from what 
I remember the maximum lobe gives only about 2 db improvement.  That's 
not trivial for DX, but I'd be surprised if it helped much for a Field 
Day type of event.  I also seem to remember that at low heights the gain 
effect is reduced, so I suspect that you'd get even less than 2 db 
benefit on the low bands.

Wow, though ... your antenna restrictions per the rules are pretty 
severe.  K7ZB and I used to travel to the Mogollon Rim country of 
Arizona (between Flagstaff and the border with New Mexico) that is the 
home for the largest forest of Ponderosa Pine trees in the world.  We'd 
shoot lines over the tops of 120 to 150 foot tall trees and haul up all 
sorts of wire antennas pre-designed (using EZNEC) and pre-built for the 
job.  Each year we'd try something different, and in 2000 we put up nine 
different antennas for different bands and different directions:

80m  - dipole
40m  - delta loop
40m  - 2 element wire yagi (full size with 20 foot poles for spreaders)
20m  - phased stack of two 2 element wire yagis (an amazing rats nest of 
wires that worked great)
20m  - single 2 element yagi
15m  - phased stack of 2 dipoles
10m  - 3 element yagi

I don't even remember what the other two antennas were, but we set an 
all time USA record that year for ARRL Field Day 2-op single rig QRP 
(broken two years later by an east coast station).

Are you allowed to change the position of the feedpoint during the 
contest (multiple selectable feedlines)?  What is the definition of a 
"single element" ... does a continuous triangle, for instance, count as 
a single element?  Are you allowed to change the dimensions of the 
single element during the contest?  There may be some possibilities for 
beam shifting by playing around with such things.

Also, what kind of ground conductivity do you have there?  If it is 
pretty good, a low vertically fed loop (a sort of squashed rectangle) 
might be interesting ... keep one support stationary and move the other.

Best of luck es 73,
Dave   AB7E

On 4/23/2010 8:28 AM, Steve GW4BLE wrote:
> Anyone have experience of using a multi-band sloping Vee beam?
> In preparation for National Field Day here in the UK we are considering
> something along those lines.
> We are restricted, by the contest rules, to one antenna which must be a
> single element having not more than two elevated supports and not exceeding
> approx 35 feet above ground at its highest point.
> We usually have a doublet, but with no real restriction on space thought to
> experiment with something different this time...
> A sloping vee with the far ends moved around to favoured directions could be
> an option.....
> Any observations out there ?
> Thanks
> Steve
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