[TowerTalk] Beverages and verticals
Jim Brown
jim at audiosystemsgroup.com
Sat Mar 18 12:31:39 EDT 2017
On Sat,3/18/2017 9:16 AM, Bill via TowerTalk wrote:
> 1. I can make them any height, but am considering 10 feet with a rise to maybe 14 over the driveway. Thoughts on the height, and the "hump' over the driveway?
Lower height makes them work to a higher frequency. Mine are over
irregular terrain, with intended height varying between 6 and 12 ft, and
often drooping to 2-3 ft when a limb hits it. They are still working on
20M, and I used the EU Beverage on that band before I had aluminum in
the air.
> 2. The NE/SW run will be running pretty evenly downhill and will drop from around 1150 feet to around 1000 feet above sea level. While this is great for a Yagi, how will it affect the Beverage going downhill? Conversely, how will the rise of 150 feet affect the Beverage in the opposite direction?
Mine are bi-directional and terminate into a rise in one direction, more
or less flat in the other. Since I have no reference it's hard to say
whether that matters.
> 3. Finally, a 4 square will be used for transmit on 80, with the same drop. Should I expect any enhancement in the direction of the drop and conversely, any degradation in the uphill direction? I think I know the answer to both questions, but want some opinions. I can't model this on N6BV's HFTA so right now it's guesswork.
N6BT gave a talk at Pacificon two years ago documenting experimental
work showing that a vertical very close to a drop-off had significant
enhancement in the direction of the dropoff. As I recall, this was on
20M. Slides are somewhere on the internet. Google is your friend. :) As
you probably know, the physics behind HFTA only applies to horizontal
polarization.
73, Jim K9YC
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