Topband: BOG Antenna Measurements

[Don Johnson]

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 at me.com
n4dj.com