[Elecraft] OCF antenna

[Art Nienhouse]

/*I have been using the K-Line for a while now with an 80 meter OCF 
dipole, mine is from Radio Works it uses a transformer balun at the top,
with 22 ft of 8x coax to a line isolator current balun at the bottom ( 
feed of the antenna) its long end is almost over the operating station, 
I have for many years run a Hy Tower 25 foot from the radio room when I 
lived up north using a Quadra amp. I always  use a line Isolator current 
balun at both end of the coax run station to antenna I modified my Hy 
Tower to remote tune on 160 with a air core roller inductor, the 
performance on 160 was very good with no problem in the shack at power 
levels over 1200 watts.

I can say the KAT-500 does not exhibit any bad behavior I have always 
used a line isolator current balun at both ends of the feed line, my 
tuner is working like is should I have never had it auto adjust on my 
during qso's. I do not run 160 meters with this set up even tho the 
antenna is called the 160 cw special I have only tested it at 500 w a 
couple of times, as expected it does not perform well on 160 meters even 
at 500 watts.

It could be a requirement for the best problem free operating to use two 
Line Isolator baluns when running power with this antenna or others like it.
My big Palstar 4k is now in the closet ever since I built the KAT-500  
mine is one of the first kits shipped I am and have been pleasantly 
surprised with the performance no more tuning from the notes.

Its truly automatic I love it, I was a bit apprehensive when I ordered 
it thinking it surly can not replace the big box but it has and then some.

There is nothing to be afraid of Elecraft as a company is far and a way 
better than any body else if there is an issue it will be fixed if you 
are looking to purchase and it fits the budget .......do it you will be 
glad you did......

Regards
Art
ka9zap*/

     I can't agree with your last paragraph. The usual problem with RF 
in the shack is traceable to a couple of factors. First, your shack is 
right there under your antenna and the RF in the shack is direct 
radiation from the antenna. However, that is not the problem in most cases.

     In most cases, RF in the shack can be traced to having RF on the 
outside of the shield when using coax or an unbalance in the current on 
open wire feeders. Usually the problem is manifest in the case of coax. 
The really good news is that there are easy fixes for the problem. The 
fix is to use a proper balun or line isolator. A proper balun is one the 
prevents currents from flowing on the outside of the coax shield. I dare 
say that most inexpensive baluns are of the voltage type. What that 
means is, if the SWR gets too high or the input terminals don't see 
equal but opposite currents, current WILL flow on the outside of the 
shield; there are several books on this subject. A Windom or OCF dipole 
will not present equal and opposite current to the balun input. The fix 
is to use a balun type that will minimize current flow on the outside of 
the shield, and that is a CURRENT balun.

     The other thing you can do is to install a line isolator. This is a 
device that is called a choke or 1:1 balun. It is nothing more than a 
bunch of magnetic material, ferrite or powdered iron, on a section of 
the coax below the feed point and balun, if used. Coiled up coax works 
also, about 10 or so turns about 6 or so inches in diameter. Taking 
these steps should make a dramatic improvement to the conditions you 
reflect.

73,
Barry
K3NDM