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Old March 18th 07, 03:22 AM posted to rec.radio.amateur.antenna
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Default Windom antennas - down to earth

Mike Coslo wrote in
:

....
Sorry for the delay in response Richard, but as a confessed
not-so-wise
guy, I've gone back to modeling to see exactly where I've erred and to
discover the source of my density.

And darned if I can't figure it out!

I've modeled Both OCF and frequency cut dipoles, and darned if
the
frequency cut dipoles don't look better.

Your argument makes it sound as if the OCF has identical
performance at
those same points as a frequency cut dipole. Resonance or not, there
are bands for which I still need a tuner, which makes the whole
purpose a little moot. The SWR curve of the OCF really doesn't look
all that hot, sometimes it is just passable at the frequencies of
interest,and looks better off frequency. and it looks like something a
radio with a *good* autotuner could take care of. That has been my
experience with them. Sure seems like a compromise to me. YMMV.


Mike,

You seem to be considering just the flat-top of the OCF and that is not
the only conductor of an OCF dipole antenna system carrying current, the
other is the feedline.

If you offset the source in a halfwave dipole (zero length feedline), I
expect you will just see an increase in feed point R, and no significant
change in loss. So on that basis you could argue they are equivalent...
but you haven't compared an OCF dipole antenna system with a centre fed
dipole antenna system.

Then you talk about the SWR curve and ATU.

Aren't you trying to compare the entire system? Is there much point in
comparing the flat-top of an OCF with a centre fed, it is only part of
the picture.

Of course, the system performance will depend on assumptions that you
make about the ground, feedline route, length, type, ATU etc... but
having chosen a scenario, you can get to an overall performance figure
that properly deals with the complex interaction between components.

Owen
 
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