[TenTec] [Ten Tec] OCF Antennas - Which commercial antenna is gest?

[Barry LaZar]

I think there is some historical perspective that is missing in some our 
discussions. First open wire was used in the early days of radio as 
there wasn't much else around. You could run a wire from your antenna 
directly to your transmitter's output, but there were really few other 
ways to go. Coax came into being somewhere around 1940, and this can be 
disputed, for the purpose of running a transmission line through a 
ship's steel bulked.  The 50 Ohm number came about because that is what 
resulted from the material at hand, or you can supply another story.


The Windom was invented to be able to use a single antenna on multiple 
bands. The original design shows that it was fed by a single wire to a 
point 1/3 down the length of the antenna, and it was mandatory to ground 
the radio. All of what we today call Windoms or OCFDs are based on 
Windom's design. None of any of these antennas were touted to be 50 
Ohms. They were sold to be workable with your transmitter if you have a 
tuner, and hopefully a good one with reasonable loss. One commercial 
version sold by Radio Works is the Carolina Windom which is a design 
that a bunch of hams in the Carolinas came up with based on Windom's 
designs. From my inference, what they were trying to do was to overcome 
the issue of having a horizontal antenna electrically low to the ground 
and still get low angle coverage. It sort of does that, and I said in an 
earlier post I bought into that argument; I'm not sorry as I was finally 
able to obtain a DXCC after 50 years on the air. The Windom is not a 
compromise antenna unless you consider trying to use one antenna for all 
bands a compromise.  I make NO consideration for SWR.

I am very cavalier about SWR as a means of determining an antenna's 
operation, except in the extreme. A 5:1 SWR doesn't bother me much. I 
only care how much I give up in transmission line losses to that number. 
On 80-~20 it's not enough to excite me, but on 10, I get a little 
careful. Unless you have a really long run the RG-8 type low loss cables 
make the discussion more academic than worrisome, and I mean like the 
Belden 9913, Times Wire LMR-400, or equal. I do not equate antenna 
resonance with an SWR of 1:1, either. There are only a few times an 
antenna is resonant and it reflects 50 Ohms.

If you have the room and can put up only one antenna, a dipole for the 
lowest operating frequency is good. Just, get it as high as you can, on 
both ends. Anything else you do is containing the SWR variations over 
the bands such that you can deal with it. If you do go with a center fed 
antenna, open wire is really good as it has the least loss of any other 
feed line. However, you will need a balun, a good current balun, as 
today's radios want to be connected to coax cable.


73,
Barry
K3NDM