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Discussion in 'CB Antennas' started by Number15, May 7, 2007.
Like MC, the only one I'm aware of is a dipole.
I figured BS.
I should have thought of that. I have an A3.
Looky here at step #4 page #6.
So the driven element is a dipole?
OK, it was BS as I thought.
I mentioned that I have a beam with the driven element being a dipole,could this be what he meant, I was told the coax was hooked to the yagi with a single driven element on a direct feed, gaining 5 db over a gamma. :frky
I figured why waste time telling him he couldn't gain 5db with anoter antenna just like it stacked.
This thread made me consider there was a method of feeding a yagi like he was trying to describe.
Check it out: Mosley Antennas!
As other elements are added to the driven element, director(s), and reflector(s), the input impedance of the driven element is lowered. Depending on the number of 'other' elements, the input impedance can get down to something around 20-30 ohms. Depends on the number of elements, their spacing, (and at times the color of the sky I think). That's why a gamma (or beta, or delta) match is then used, they tend to raise the input impedance back to something around 50 ohms. Feeding a multi-element beam directly can still be done but usually a balun is needed to get that 50 ohms back (but then you may not consider it directly fed anymore).
There is no 5 dB difference between matching systems, that's about the only B.S. about the whole thing (unless it's MY antenna, and MY antennas are always 5 dB stronger than anybody elses! You believe that too, right?).
Ain't this electronic @#$% fun?
The BS is, as I see it, is to simply eliminate a gamma and hook the coax to a one piece driven element.
Maybe I'm missing something.
For some reason adobe has gone to heck on this computer, so I couldn't see the pdf link above.