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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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