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Re: Topband: BOG Antenna Measurements

To: Topband <topband@contesting.com>
Subject: Re: Topband: BOG Antenna Measurements
From: Don Johnson <n4dj@me.com>
Date: Tue, 05 Feb 2013 10:16:44 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Thanks to all for comments concerning my post a couple months ago inquiring 
about BOG impedance.   The short story is since then I have determined that one 
of my BOGs must have a feed point impedance of approximately 400 ohms at my 
location in New Kent County, just east of Richmond, Va.  

The long story is that I decided to document my Beverage construction and 
measurements on my website. At times this is a daily occurrence. What has 
resulted has become what some may call a "Beverage Blog".  What started as a 
desire to wind the right ratio transformer and pick the right termination 
quickly started getting larger.  Questions about so called "water proof" 
connectors came up etc.  As a result, I will include a few things which should 
be good practice because I discovered, for example, that everyone does not tape 
their connectors when they are out in the weather.   Also, just because a 
dealer says a connector is "water proof"  that may not mean water will not find 
its way in!  

I thought I would post the link for anyone interested.     
http://n4dj.com/Beverage.html

If you read it, remember that it is a work in progress and I do not have the 
best test equipment. Any numbers noted are "ballpark" and things like 
terminating impedances vary considerably, depending on ground composition, 
distance to ground, and many other factors. 
There are some charts, plots and tables.  I like to use EZNEC. I am learning to 
use cocoaNEC (for the MAC)  Some of the tables I worked up were using formulas 
that are common in the antenna text books. They also appeared in the ON4UN book 
as well as H.H. Beverage's papers.  I  try to explain my thinking as I go, 
right or wrong. We learn a lot from our mistakes. I will try to document a 
mistake and what I learn from it.  For example, from reading what I could find 
on BOGs, I first assumed that the BOG impedance was much lower than what I have 
measured.  I probably just did not find the right things to read. I do not 
think I am alone in doing that!  There is a wealth of bad information on the 
internet. I hope I am not adding to it. 

So far the Beverages I have, two on the ground and one in the air are working 
well beyond my expectations!  

73,
Don
N4DJ

n4dj@me.com
n4dj.com
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