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Re: Topband: cutting coax stubs for 80 meter 4-square

To: terry burge <ki7m@comcast.net>, w5zn@w5zn.org
Subject: Re: Topband: cutting coax stubs for 80 meter 4-square
From: "Richard (Rick) Karlquist" <richard@karlquist.com>
Date: Sat, 9 Jun 2018 17:07:21 -0700
List-post: <mailto:topband@contesting.com>
As a sanity check, terminate the coax with a 50 ohm resistor and verify
that you have good coax.  Flat line at 1:1 SWR, etc.

Rick N6RK

On 6/9/2018 4:57 PM, terry burge wrote:
I don't know what is wrong here but I keep getting in this situation where my 
typing starts running back over my writing. I will try again to reply.


Joel,

I have tried all that the manual says without success. All I see is the 
horizontal solid and dashed lines of R and X. No indication of a resonance 
point anywhere from 1880 KHz up to 10,500 KHz. Go figure? At least my mfj-259b 
is working old as it may be. Rig Experts is going to get a nasty note I think. 
Disappointing, huh?


Terry

KI7M


On June 9, 2018 at 2:54 PM Joel Harrison wrote:


     Hi Terry,

     I replaced the 1/4 lines on my 80 meter 4 square this past fall and used
     my AA-170 to set the length with no problem.

     Just select "all" for the mode and set the freq you're aiming for and then
     trim the line until X equals zero with the far end open. Should work fine.
     I always calculate the length x VF then add a few feet to start.

     73 Joel W5ZN

         > > Hi guys and gals,


         I have got DX Engineering 75 ohm foam coax to make the stubs/feeders 
for
         my Comtek 80 meter 4-Square and am finding some difficulty. Neither my
         MFJ-259B nor my Rig Experts AA-170 seem to indicate a 1/2 WL at 7500 
KHz
         or a 1/4 WL at 3750 KHz? Or any frequency up or down from there. Seems 
to
         me the last time I did this a few years ago I didn't have a problem
         getting a 1/2 WL dip indicating a resonance location. But now I just 
don't
         get any indication of a resonance.


         DX Engineering said they had got some 75 ohm foam coax that instead of
         0.84 VF was more like 0.80 down to 0.76 VF. But checking all the way 
down
         to 6000 KHz on 40 meters or 2500 KHz on 80 meters fails.


         My test is to use either antenna analyzer with a PL-259 installed at 
one
         end and an open or a short at the other. I started with 57'7" of coax.
         Tried both with the coax in a roll and strung out. What am I doing 
wrong?


         Terry

         KI7M

         😞
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