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SWR

Jul 11th, 01:51

WA6ZFM

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I have noticed, at times, that my SWR meter reading fluctuates, wildly, even after initially tuning to 1:1. I will be transmitting with a 1:1 but, all of a sudden, it will jump up then come back to 1:1. What could cause this sort of thing?

Richard
Jul 11th, 02:06

9V1DB

Joined: Aug 10th 2011, 09:34
Total Topics: 0
Total Posts: 0
Richard, it could be something as simple as the wind blowing your antenna around. I use and end fed wire hanging vertically out my window. When the wind gets to a certain velocity, and the wire get about 30 degrees or more from vertical, my SWR's go crazy.
Jul 11th, 17:28

WA6ZFM

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Yes, thanks 9V1DB. Could be.

One leg of my ALPHA DELTA DXCC, as an inverted vee, passes through a pine tree. I went out, this morning, and clilpped off some of the branches near the antenna wire. I'll see if that helps.

Richard
Jul 11th, 20:10

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

Even if the wire is insulated, you can still get significant capacitive coupling to live foliage. The effect is more pronounced at the high impedance ends of the antenna.

With a 40M dipole, I was able to reduce my mid-band SWR from 1.5 to 1.2 by cutting off a maple tree branch that was up against the end of the dipole.

Zack W1VT
ARRL Senior Lab Engineer

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