IF the feeder end at shack shows 3:1, you could have a loose connection to
the antenna on only one side, or it could be a balun, or cable choke loose,
or with water infiltration.
One of the ways to catch a opening up of a feedline, is to put a 100,000 ohm
resistor across a split feed, if that is what you beam has. When the beam
has a good feeder, (both sides connected), you can measure 100,000 ohm
resistance plus the resistance of the lenght of feedline times two. If one
side of the feeder comes loose, you no longer measure 100,000 ohms. The
resistor is such a high value, it has no effect on your much lower RF
impedances at the feedpoint.
Unfortunately, you most likely have an open connection problem, rather than
a trap problem,since it is on all bands. Or should I say fortunately, as a
feedpoint problem is a lot easier to fix than a trap problem when the trap
is out there on the element. At least the feedpoint is accessible by
climbing the tower, if so equipped, and the rotating mast is not too tall.
Stuart
K5KVH
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