[TenTec] The OCFD Mystique

[Barry LaZar]

Fellas,
     There is nothing magic about an OCFD. It just a variant of the 
Windom that was invented, I believe, in the 1920's. It's nothing more 
than a dipole fed off center so that when you use it on even multiples 
of a 1/2 wave the impedance is either 50 Ohms or in the region of what 
your tuner can handle. If you can get it up 35 or more feet, it does 
make for a pretty good all around antenna. I have a variant called a 
Carolina Windom. It's up about 40 feet and I've worked DXCC, mixed CW, 
and phone. I've also gotten my WAS using it and 100 Watts.

     The issue of SWR is a red herring. So long as you can tune the 
"system" such that your rig can accept what the tuner gives it, that is 
really all that matters. Yes, there are losses associated with high SWR, 
but if you use low loss transmission line, the additional loss due to 
high SWR can be pretty trivial, a 1db or so, depending on SWR and band 
being worked. On 10 meters my system losses total around 2 db which 
includes everything behind the tuner.

     One thing that must be remembered is that the transmission line from 
the antenna to the station can be an impedance transformer if the SWR is 
greater than 1:1. What this means is that what you measure at the 
station may not be reflective of what the antenna is reflecting. So, 
some of the comments about this antenna works well over all but this 
band or another may not be accurate unless the effects of the length of 
the transmission line is included.


     Bottom line from here is put up 66' or 132' of wire. Feed it ~ 1/3 
of the way from an end. Use a 4:1 current balun if you don't want the 
feed line to radiate or voltage balun if you do. And, if you force the 
feed line to radiate, put a good RF choke about 15 or so feet down from 
the antenna feed point point, load it up, and start working the world. 
Just remember to use a good low loss coax like Belden 9913 or Times Wire 
LMR-400.


73,
Barry
K3NDM