Topband: Terminating System for Beverages

[Tom Rauch]

Hi Fritz,

> I'm planning to put up several beverages on a farm that has cattle grazing
> all over it.  For obvious reasons gradually sloping the beverages to
> ground level at both ends would require quite a bit of extra fencing to
> keep the cows away from the wire.

I have a similar problem. There is no need to slope the wire, it does 
not reduce the vertical pickup off the ends unless the slope 
extends a very long distance. 10 feet of vertical drop is ten feet of 
vertical drop. 

For an example, consider the K9AY loop or the Pennant antenna. 
They use a sloped side (or sides) and the sides behave like a short 
vertical, despite being sloped.    

The ends of my Beverages slope a few feet, but just for mechanical 
reason to reduce leverage on the end posts. My wooden end-posts 
are five feet high so they don't need to be back-guyed.

> beverage?  At the terminating resistor end of the beverage, the resistor &
> capacitor would be 10ft off the ground and then the coax would go
> vertically 10 ft down to a ground rod.  Similarly, at the feed point end
> of the beverage, the matching transformer and feed-line connection would
> be 10 ft off the ground.

I think you are seeing a capacitor isolating the ground so voltage 
can be applied down the Beverage? At least that is what I recall in 
my newer edition.

You can do anything you like with capacitors and shields, and you 
will have exactly the same "vertical pick up " at the ends of the 
antenna. Vertical pick-up will be exactly the same as a single 
unshielded wire. If there was a way to shield a system for good 
common-mode currents and not bad ones, and someone 
discovered it, they would be rich!
 
> If the answer to the previous question is yes, then is there any problem
> with several beverages "sharing" the same "ground system", i.e., a single
> capacitor and 10ft length of RG-62, at the feed point end?

Beverages should never share a common ground. The common 
ground is a path where the unused Beverages will "pump" the 
ground system's finite resistance up-and-down with their signal, 
and it will couple to the Beverage you are using. Another way of 
looking at this the unused antennas become part of a radiating 
ground system for the used antenna.

The ends of separate Beverages should always be kept at least a 
few times the height plus several feet apart, and especially not 
share the same ground system!


73, Tom W8JI
W8JI@contesting.com