Gentlemen,
This Spring/Summer/Early Fall project is to attempt to erect an 80m wire 4
square off my tower, but using Folded Counterpoise(s) for each element. I
don't have enough property to use elevated radials, and the next door
neighbor is difficult to deal with.
I'll be using a Comtek box for phasing. My understanding is that the
feedpoint of each element needs to be ~ 35 ± 0 ohms for the system to work
correctly.
I'm not exactly sure what the feedpoint impedance of an FCP with a 1/4
wavelength element is supposed to be. I assume from K2AV's article that it
will be close to 50 ohms.
I do have the isolation transformers for the FCPs.
So, my plan is this:
1] Erect element #1 with an FCP.
2] Use my Zoom 230, a length of coax, and calibrate the Zoom 230 with an
Open, Short, Load at the end of the test cable.
3] Measure the feedpoint impedance.
4] Use SimSmith to calculate the matching network to transform the
impedance of the feedpoint to 35 ± 0 ohms.
Questions/issues:
1] The isolation transformers are from Balun Designs and are inside the
typical 4" x 4" x 2" grey PVC box. My plan is to remove the SO-239
connector on the box, and add a second grey pvc box "side to side" but with
the covers 180° from each other. Then drill holes for the "hot" and ground
wires from the transformer toroid, so that they can enter the second pvc
box (keep them separated). Then use the empty box for the transformation
network, and connect it to a SO-239 mounted on the box. Having no idea
what the impedance is, do you think that would work?
2] Do I tune the element/FCP to resonance (where the reactance is 0) first
(~ 3.55 MHz, as per the Comtek manual) THEN measure the impedance, and
build the network? Or do I just "get close enough" with the element/FCP,
then build the network, and then adjust the element for ~ 3.55 MHz?
Or, am I not asking the right question(s)?
Private replies with step by step instructions are welcome!
Thanks!
Tom, N2SR
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