[TowerTalk] OCF dipole

[jimjarvis@comcast.net]

TT:

Been reading Bill Meeker's OCF dipole saga, and communicating privately with him.

Jack Belrose, VE2CV, wrote a series of articles for QST over 10 years ago, analysing the OCF dipole, and designing a 'balun' to handle the varying complex impedance presented by the off center feed.

In reality, what is needed is an "un-un",  and Sevick's work may prove helpful, as well.

For whatever value it may have, I was inspired to try an OCF dipole by Belrose,  as a general purpose antenna.   To save time, I used a commercial product....the "Carolina Windom", of which I've now had several, in both 160 and 80m configurations.    Radioworks makes and sells these things, and has resolved the matching solution to a satisfactory degree.

As both K4SAV and W8JI observed, an unbalanced antenna will tend to have current on the outside of the feedline.   The CW is no exception.   My solution is use of  ferrite chokes in the feed system,  on a ground point directly below the antenna.   The coax shield is grounded through a bulkhead connector fastened to the ground rod.  Clip on ferrites both upstream and downstream of this point tamed the common mode problem.   

N2EA