Re: High SWR on 20 and 40

Posted by djmd on Jan 16, 2010; 12:34am
URL: http://elecraft.85.s1.nabble.com/High-SWR-on-20-and-40-tp4401077p4402287.html

It's the BL-2 switched balun that I have been using, and have tried both modes. Forgot that detail. I have also tried one of those baluns built from PVC - can't remember the manufacturer. It's a 1:1 as well. Same results.

No analyzer yet, but I really should think about getting one. Planning on a lot of antenna experimentation this year.

I have actually thought of eliminating the coax. I'm not sure if I can use the same route as the coax, with the metal window frames, gas pipe, water pipes, all nearby in the basement. But what about going right through the brick? I would not be opposed to doing something like this.

And re: your follow up - all the testing was done with the KAT2. I have never disconnected it.

I also should have mentioned that I do plan on using this antenna system with my old radio as well. Only 10w on the K2, but 50 or so with the Yaesu as well. (mostly digital and CW.)

Don Wilhelm-4 wrote

Dave,

Is that a 1:1 balun or a 4:1 balun.  Usually a 1:1 works better, but
whichever balun you are using, try the other one and see what happens.
Do you have an antenna analyzer?  or can you borrow one?  If so, what is
the impedance at the end of the coax?  Both the resistive and reactive
components please - just the SWR does not provide much information on
how to advise you to proceed.

You may be better off eliminating the coax entirely and running the
window line all the way into the shack.
73,
Don W3FPR

djmd wrote:
> Hello,
>
> I have been trying to troubleshoot my antenna system, and have been trying
> to avoid the dreaded "high swr" post, but I've run out of ideas, so I'm
> turning here.
>
> First let me explain my system. 67' dipole fed by 16' of window line. That's
> connected to an Elecraft balun. From the balun, there's a short piece of
> coax going to a barrel and into the basement (through a piece of cement
> backerboard. From inside the basement, there is another piece of coax, about
> 12', connected to the barrel, and going up into the bedroom directly to a K2
> with an autotuner.
>
> Before the K2, I was using a Yaesu FT840 with an MFJ tuner. After tweaking
> the window line length and the actual length of the dipole, I never really
> had a problem with SWR (well, according to what the MFJ was saying, which
> may or may not be totally accurate.) Usually 1.5:1 or under on all bands.
>
> With the K2/KAT2 in place, the SWR reported by the tuner is all over the
> place. The only one that gets less than 1.5:1 is 30m. Most bands are pretty
> random, anywhere from 3:1 to 7:1. However, on 20 and 40, it generally does
> not get below 9.9:1.
>
> I've tried 4 different lengths of coax between the barrel (inside) and the
> rig... 3', 6', 12' 20'. I've tried a couple different lengths between the
> balun and the barrel on the outside.
>
> When I attach the balun directly to the K2 I get <1.3:1 on all bands (most
> are 1:1.) With a short piece of coax between the rig and the balun, I get
> the same results. I've also attached my dummy load to the barrel on the
> outside of the house, and tested it from the shack, and I saw 1:1 no
> problem.
>
> I totally understand the concept that if "A" works and "B" works, "A+B"
> doesn't necessarily work. I understand it's a whole system. But I've tried
> so many different combinations of coax on each side, and don't understand
> why my SWR is basically infinity:1 on 20 and 40, when they seemed to match
> reasonably with the old system. I have not tried different lengths of window
> line between the dipole due to the fact that I had it perfectly trimmed for
> my old system. But I have plenty of it and would be open to trying anything.
>
> Just trying to get the most I can out of my modest 10W. :) Any suggestions
> would be appreciated!
>
> 73,
>
> Dave
> K8DJW
>  
>  
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