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Author Topic: FMUser CP100 elliptical circular antenna (CZH) - anyone have this?  (Read 113 times)

Offline chanito

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screwed with one for 4 hours today and could not get it down lower than 2:1 SWR best case and only on the lowest part of the band. Also, how the heck does it mount? The diagram shows it stuck on top of a pole in line with the pole. Never seen a CP antenna mounted like that. I stuck it on sideways like it looks like it is really supposed to be, but not geed results.
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Offline redhat

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Re: FMUser CP100 elliptical circular antenna (CZH) - anyone have this?
« Reply #1 on: November 15, 2020, 0249 UTC »
I've built a number of them over the years as emergency antennas for stations.  The length of the elements sets the resonant frequency, the position of the arms adjust the match.  The two do interact.  It should be mounted with the feedpoint straight up.  Also proximity to its mounting structure and size of such will also affect the match and center frequency.  Usually the match was around 1.2:1 or so.

A sweepable analyzer of some sort will make life a lot easier.  I now use a return loss bridge and a service monitor so I can see the adjustments in real time.  Doing it the old way with an exciter and a wattmeter was always a maddening experience.

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« Last Edit: November 15, 2020, 0254 UTC by redhat »
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