[TowerTalk] How to mod a 40m 4-square for 10m use?

[Joe Subich, W4TV]

You've asked this question before in a different form.  Check the
archives for the prior thread.

> I'll PRESUME the capacitors need to be a different value in the
> exterior switch box, but to what?...anyone have a schematic for a
> Comtek 4-square? (the outdoor portion)
You will need to change *both* the capacitors and the inductors.
Formulas for both inductors and capacitors are here:
 
<https://www.researchgate.net/figure/Transmission-line-and-lumped-element-based-a-90-coupler-and-b-phase-delay-cell_fig2_224208944> 


The inductors should probably be wound as a bifilar pair on a properly
sized toroid core for the desired power level.

As an alternative, you could replace the lumped circuit with a coaxial
"rat race" as shown in the upper left of that same reference.  Since
50/(2)^.5 = 35 Ohms, the two "horizontal" legs can be a pair of 75 Ohm
cables in parallel with only minor impact.

73,

    ... Joe, W4TV


On 2022-01-22 5:22 PM, Mike Smith VE9AA wrote:
> I am trying to go to all 4-squares like my contesting 4-sq buddy John, N8UM
> in TN.
> 
> I am nearly there, having just installed a 15m one in time for CQWW CW.
> 
> There are no new dedicated 10m 4-squares to be found commercially, if my
> internet searching skills
> are telling me the truth, so recently I bought a 40m 4-Square (Older Comtek,
> NOS)  and am hoping to mod it for 10m, but I have no idea where to start.
> 
> I'll PRESUME the capacitors need to be a different value in the exterior
> switch box, but to what?...anyone have a schematic for a Comtek 4-square?
> (the outdoor portion)
> 
> Apparently Tim, K3LR (DX Engineering) was not happy with the performance
> from the 10m Comtek 4-squares, so is not selling them anymore. I can
> definitely respect that decision to not produce a top-notch product.  I am
> not looking to squeeze every fraction of a dB out of a 10m array.  I just
> want something that 'works', is directional and has some modest amount of
> gain.
> 
> (I have built several K1WA/K8UR arrays and am not totally happy with them)
> 
> My SO2R contest station uses a single horizontal antenna on the 2nd radio
> and a bunch of vertical 4-squares on the primary radio.
> 
> Any ideas on the Comtek Mod fellas?
> 
> Tnx
> 
> Mike VE9Antenna Antenna
> 
> Mike, Coreen & Corey
> Keswick Ridge, NB
> 
>