Try the test with a different rig.
-Mike
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Tony
Sent: Thursday, December 22, 2011 12:52 PM
To: towertalk@contesting.com
Subject: [TowerTalk] SWR Problem Balun or lightning protection? Problem
solved?
All,
This has become a real mystery folks. I checked the SWR on my 3 element
Steppir today and found that it behaved the SAME as my 5 element 20M mono
band Yagi, i.e., the SWR increases after keying down for a few minutes and
returns to normal after waiting a few seconds. This happened with all bands
on the SteppIR. The antennas are mounted on the same tower about 12ft apart
so I always retract the Steppir elements when using the 20M mono bander to
avoid interaction.
Today, I temporarily "solved" the problem by adding a shorter piece of coax
between my rig and amp essentially shortening the total length of coax
feeding each antenna by a few feet. I can now key down without any problems
and the SWR curves on both antennas have returned to normal.
The bad news is that the problem comes back when take the new jumper out of
line and connect the rig directly to the separate coax cables that go up the
tower to feed each antenna.
My guess is that it's unlikely for both antennas to behave the same way
because of balun issues or some other problem with the antennas. As for the
coax, it's high-end Bury Flex that's a few years old; I carefully soldered
and waterproofed the connectors myself. I'm also using the same batch of
coax on other antennas and they work fine.
The only changes I've made recently was adding 2" copper straps to connect
the tower to the ground rods and Polyphaser lightning protection to the
rotator and SteppIR control cables.
Just to be clear, the SWR issues happen with or without the coax being
grounded via the Polyphaser lightning protection; that's either a direct
connection between my rig and coax that runs up the tower or with the
grounded lightning protection in line.
I'm glad all is working fine with the new shorter jumper that changed the
overall length of the two coax cables feeding each antenna, but it would
seem something is still not right. It's probably a long shot, but I'm going
to remove the ground straps from the tower and see if that makes a
difference.
My sincere thanks to everyone who took the time to reply.
Tony, K2MO
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