Re: High SWR on 20 and 40

Posted by Julius Fazekas n2wn on Jan 16, 2010; 2:33pm
URL: http://elecraft.85.s1.nabble.com/High-SWR-on-20-and-40-tp4401077p4404398.html

Dave,

Have you tried putting a dummy load in line and seeing if the tuner will tune 1:1 with it?

This might tell you if the problem is in the tuner. You could also place the load further along the coax and see if the problem disappears.

My KAT2 can tune almost anything it seems, but it is possible that your bridge diodes got zapped and that would cause problems.

73,
Julius
n2wn

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