[TowerTalk] C4XL Driven Element Placement

[K7LXC]

In a message dated 97-12-24 10:50:33 EST, k5qf@camalott.com writes:

> When I
>  measured my 185 inches from the end of the boom for the ez mount boom to
>  mast bracket it placed it going thru the hairpin tuning of the 40 meter
>  element here.The swr is fine and where it should be on the ground but
>  droppes to 4.26mhz when My tower is cranked up.:(.Does anyone out there
>  have the measure meusurement between that 40 meter driver and the coller
>  on that boom section.Or have any measurements at all so I can get this
>  antenna fixed.

     When you say the SWR is fine on the ground, do you mean ON the ground or
what? What height are you testing it at? Where are you measuring it on the
antenna? What's in line with the feedpoint? Are you measuring the same
feedline when it's up in the air? What are you using to measure the SWR? If it
is on the GROUND, it should still look like an antenna (take power, have some
sort of resonant point and fat SWR curve). If not, something's wrong. 

     First, I've installed a bunch of Force 12 antennas including numerous 40M
configurations. The measurements in the manual will give you a place to start
but are not necessarily the finished dimensions. I would suggest using an
instrument like the Autek or MFJ that you can put right on the feedpoint. Take
a measurement there to eliminate everything else in the feed system. That'll
be your benchmark. 

    Why don't you measure the feedpoint with the antenna on the mast and the
tower cranked down? I've found that it's much more meaningful than
measurements on the ground (see comments above). As long as the elements are
spaced properly on the boom, all you should have to do is tune the 40M
elements per the procedure and the resonant frequencies in the manual and the
antenna will work as advertised. You can tune the antenna with it mounted on
the mast by removing all but one of the boom-to-mast clamp bolts. Then tip the
boom until you can reach the out-of-reach element. Tune it up and pivot it
back into place. Tune the driven element and you should be in business.

73,  Steve  K7LXC

     

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