I do have a series capacitor. I was giving you the design impedance without
the gamma match and the measured impedance. I used one wavelength of feed
line so I could get the antenna off the ground. It is a multiple of 1/2
wavelength which should reflect the same impedance as the feed point.
Chuck W5PR
Whoa.
A gamma match has TWO things to 'change' ... one is the point of
attachment from gamma rod to the driven element ... the other is the
SERIES CAPACITOR in the gamma line.
All gamma matches that I use are tuned by placing the antenna analyzer
about ONE FOOT from the feedpoint, then going back and forth between
the capacitor and the shorting bar .. until the match is what I want
it to be.
The inductive portion of your measurement seems to be due to NOT
having a series capacitor in the gamma match.
73
Don
N8DE
Quoting Chuck <w5pr@swbell.net>:
> I hate adjusting gamma matches through trial and error. I am hoping my
> new antenna analyzer will help.
>
> I computer designed a 10 meter Yagi which designed at a feed impedance
> of 31.2 + j18.3. This is inductive, I assume.
>
> I have a gamma match, the antenna mounted at 15 feet and my antenna
> analyzer says (through an analyzer measured 1 wavelength 50 ohm feed
> line) Z=66 ohms, X=-52 ohms and C=105
>
> My take is to move the tap closer to the boom until it is about Z=50 ohms
> and, if there is still a negative X, to lengthen the DE. Of course, the
> changes will interact with each other and I will need to go back and
> forth until Z=50 and X=0.
>
> Am I on the right track?
>
> Chuck W5PR
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