On 10/17/16 3:06 PM, N5KM - Kris wrote:
Hi All,
A quick question about tuning an 80m 4-square. My 4-square is made from
suspended wires.
The NE and NW verticals are full size. The SE and SW verticals are 42 feet
tall with T-loading.
I'm using the Comtek hybrid box for phase control. When tuning the
individual elements what
consideration, if any, should be given to the fact that two of the elements
are shortened?
My design frequency will be 3650 KHz. In an ideal world all elements would
be identical and would
be tuned, say, 5% lower than the design frequency. My concern is that maybe
the shortened
elements will have to be tuned differently or that the 75 ohm feedline will
have to be something
other than 1/4 wl (times vf) in length.
In the past I've just tuned all 4 elements the same and it appears to work
OK like that. I'm just
wondering if there's any improvement to be had.
Any thoughts?
The standard 4 square uses the "quarterwave" current forcing technique,
And then you have some form of 90 degree quadrature hybrid or network to
get the phasing right. if the elements have "unusual" impedances, then
the impedance seen by the phasing box will be different. However, in 4
squares, the mutual impedances aren't well controlled, so the feedpoint
Zs could be all over the place. I suspect that the phasing box is
moderately insensitive to the impedances at the coax.
Kris, N5KM
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