TopBand: Beverage Box Hum

[W8JITom@aol.com]

In a message dated 97-01-10 23:17:54 EST, you write:

>Well I'll be,  it did. Its hooked to the same ground stake the Box is on.
>Some folks said it didn't help much when they tried it, but my intent was to
>get a little more bounce off the unterminated end of my backwards European
>bev.   The Beverages are noticeably more directive, and the European one is
>louder off the back now. The bev crossing the radial field is quieter also.

I wonder if you are using the simple method of just ghrounding one wire at
the far end for reflection??

If so, and if you want greatly improved performance, use a real reflection
transformer at the far end.  Grounding one wire does NOT cause a 180 degree
phase reversal that properly excites the Beverage as a two wire transmission
line returning to the transmitter, that method simply puts the current and
voltage out of phase with each other. What we really want is the current in
each wire 180 degrees out of phase in the transmission line mode, and in
phase for common mode excitation.

You can easily prove the one wire grounded one wire floating with a few
current measurements in the wires.    

Putting a ground (counterpoise) wire under the antenna seems OK. That has
never hurt my Beverages, and seems to help. It reduces current taper in the
antenna greatly, allowing more F/B ratio.
 
>THE PROBLEM
>
>Now I have a problem.  Signals on the bev's sound like polar flutter.  At
snip]
>The ground wires are not grounded at the far ends, only at the origins
>(directly to the ground stake the Box is mounted on).

It sounds like something is oscillating, and that indicates an RF ground loop
problem. 

Why do you not have the far end of the ground wire terminated in a ground
system? Or do I misunderstand you?

73 Tom

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