Topband: RE: BOG antenna notes

[Tom Rauch]

Hi Fritz,

Some food for thought....

> I've got a couple 260ft terminated Beverages that are abt 5ft high. 
>  Several weeks ago, Earl, K6SE, was nice enuf to do a little analysis
>  with 
> EZNEC.  What he discovered was that a 260 BOG (Beverage on the ground)
> had a better F/B than the 5ft high Beverage (40 vs 25).  The elevation
> patterns were pretty close, 40.1 degrees for the BOG and 41.8 for the
> 5ft.  So this past weekend, I did a little experiment.


What is an elevation pattern? If it is TOA, it is an often-misused 
term with antennas. The important thing is the absolute response 
at the desired angle compared to the response in directions of 
noise when receiving, and the absolute gain at the desired angle 
when transmitting.

I've commonly seen people use the wrong antenna because they 
consider TOA as an important concern, instead of looking at gain.  

Also models tend to fall apart with wires near earth.

A wire closer to ground looks electrically longer and generally has 
more loss. You could obtain better results loading the wire 
periodically with inductive loads, and using normal height.     

> this wasn't a good match, but it was either that or nothing).  The BOG
> was terminated with 184ohms and the 5ft one with 276 ohms (this is
> what Earl's model suggested).

Did Earl's model have "perfect ground connections" at each end? 
Did you account for the RF resistance of your ground connection in 
the termination?

With a single ground rod several feet deep, I measure about 100 
ohms or so RF resistance on 160.

 
73, Tom W8JI
w8ji@contesting.com


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