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[TowerTalk] problems with 10m COMTEK 4 sq unit

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Subject: [TowerTalk] problems with 10m COMTEK 4 sq unit
From: (
Date: Mon, 19 Mar 2001 18:32:03 EST
In a message dated 3/19/2001 11:55:23 Eastern Standard Time, writes:

> I have a 4 square on 10 meters with the Comtek hybrid and it works perfect.
>  I am using 4 ground mounted 1/4 wave verticals with 20 radials under each.
>  I have no power in the dump load at 28.3 and a 1:1 VSWR across the band.
>  The front to back is outstanding at 25 dB.
>  The antenna elements or the 75 ohm lines are probably your problem.
>  I suggest you check your set up and wiring.
>  73,
>  Tim K3LR

Thanks Tim,
from the posts I gather that Comtek unit is looking for 50 ohm antennas, then 
transforms the impedances using 75 ohm quarter wave lines to 100 ohms, which 
are then paralleled to get back to 50 ohms (two radiators at 0 deg), which 
should be the impedances of the hybrids. 
As I mentioned, my 160 and 80 units have around 46 ohm impedance (and X=3) at 
the TX port when loaded with 50 ohm resistors on all ports (no antennas, no 
cables). My 10m unit gives me around 70 ohm R and X around 20 and high SWR. 
Is that "normal" on 10m?
I will try 50 ohm radiators. No word from Jim yet.

As far as why in the world would I want 4 square on 10m? For contest 
purposes, this is to complement other antenna artillery for single OP, 2 
radios, on the same band setup. 4 square gives polarization diversity, quick 
direction switching, good clean pattern and when used at the ocean front, 
good low angle performance beating Yagis. 
Also possibility to hitch it with other antennas via Stackmatch for extra dB 
in the favorite direction.


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