[TowerTalk] Tuning a 4-square with different size elements

[jimlux]

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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