[TenTec] OCF antennas evolution

[Stuart Rohre]

Some of us have also had good results with variations of the G5RV, using 
a stub of parallel llne and transitioning to Coax without a balun at 
that point.  Varney in his original design, ran parallel line all the 
way to the shack. Is going to coax after the stub unbalanced?, sure. 
Did it work? With 60 feet of coax from the stub to the rig, it worked 
very well, usually without a tuner on 40 and 20.  The angle of take off 
or efficiency seemed suspect on 15; but it accounted well for itself on 
favorite bands. It was necessary to have the stub come off horizontally 
from its junction with the feed point, since the trees holding the 
antenna up were not over 40 feet high at the attachment points.  Thus, a 
40 foot stub could not hang vertically, with the house under it.

One can be very happy with an antenna that does the bands you prefer. 
The flat top for my version of the G5 was a variation of the ZS6BKW 
design that tries to provide for WARC bands as well. About 92 feet as I 
recall.

The main point of discussion is it seems easiest to put up symmetric 
antennas to preserve balance in a dipole.  If you don't feed in the 
center or with balanced line, you may find some issues.  You then deal 
with them, and since I come at things from a minimalist approach, if I 
don't have RF in the shack from feeding a balanced system with coax, 
that is OK.  If I had RF in the shack, I would rearrange the antenna as 
a system to correct that, or at least find the cause, and do something 
to deal with it.

The OCFD solves some very real problems for hams.  One is lay of the 
land, where you might have difficulty center feeding a long dipole in 
your available space.

In a vertical dipole, one end is coupling to earth by proximity, while 
the upper end does it to a lesser degree.  To restore symmetry there, 
you can make one end longer than the other, especially when making a 
multi band stub decoupled dipole. Making it an OCFD eases the provision 
of multiple bands on one vertical system.

In the end, the success of any antenna is can you match it conveniently, 
and does it produce contacts?

-Stuart Rohre
K5KVH