[Elecraft] OCF antennas

[Tony Estep]

On Fri, Mar 9, 2012 at 3:50 PM, Bill <bill at w2blc.net> wrote:
> I have found the easiest single antenna to utilize is the OCF...
============
The OCF has advantages and can work very well. I have had good success
with several versions, and in fact published an article in QST about
one such setup (March 2006). It's important to note that any OCF
antenna will have common-mode current flowing on the feedline, which
will produce RF in the shack. With modest power this is usually not a
problem, but as power goes up, the effects get worse.

If the antenna is coax-fed, the common-mode RF can be choked off with
a 1:1 balun or an isolator. If it's fed with balanced line, it should
go to a balun and thence to a coax link to the transmitter, and that
coax should have provisions for choking the RF. The cold side of the
isolator should be grounded to a good RF ground (i.e. not just a
ground rod or water pipe -- ideally, a counterpoise or radial system,
or other really good RF sink). The feedline will radiate, and this
should be included in your EZNEC or other model when determining the
radiation pattern.

Tony KT0NY




-- 
http://www.isb.edu/faculty/facultydir.aspx?ddlFaculty=352