Weird antenna problem

Mike Langner mlangner at SWCP.COM
Tue Jun 23 12:16:32 EDT 2009

Weird antenna --

Interesting problem !

Suggestions --

Try your procedure but don't use any contact cleaner.  See if the mere
movement "fixes" it.

If you have a low power "Antenna Analyzer" like the MFJ, try it from the rig
location.  It's low enough power that it shouldn't "weld" across an oxide
barrier.  When you have the fault -- either showing on the Antenna Analyzer
or because of low signals in your receiver, tap on or shake any
connectionors/connections and screwed-together or otherwise pressure joints
in the system.

Try transmitting.  If it's an oxide barrier between two metals, the
transmitter power should instantaneously "weld" across the oxide barrier,
bringing the receiver immediately back to life.

If these tests indicate that it is an "oxide between two connections"
problem, head to your local home improvement store.  Get a tube (toothpaste
tube) of the gunk electricians use to coat dissimilar metals, particularly
aluminum, when making connections.  It's sold under names like "No Oxide,
"NoOx," and similar.  Disassemble the/any suspect connections.  Apply the
gunk and see if it works. The paste is conductive, so don't get it across
any insulators.

The ultimate "fix" is not cheap -- electric utilities use a silver-bearing
past for high-current clamped-together connections.  "Cool-Amp" and
"Conduct-O-Lube" are two of the popular ones.  One ounce will last a typical
ham for a lifetime.

I had this same problem with my multi-band vertical until I removed the
sheet metal screws that hold the coil wire to the skirt of each trap,
replaced the screws with slightly oversize ones to get a better "bite," then
put stainless-steel radiator hose clamps around the traps over the heads of
the screws and tightened the clamps pressing the screws very, very firmly
onto the wires and the trap skirts.  No more problems!!

And I used the silver paste "Conduct-O-Lube" on AM broadcast directional
antenna 5kW to 50 kW antenna changeover contactors (relays) sliding contacts
for many years with great results!

Good luck !!


-----Original Message-----
From: Boat Anchor Owners and Collectors List
[mailto:BOATANCHORS at LISTS.TEMPE.GOV]On Behalf Of Schichler, Alfred (GE
EntSol, Digital Energy)
Sent: Tuesday, June 23, 2009 8:05 AM
Subject: Weird antenna problem

I'm not sure if this is the right group to ask about this problem, but I
figure I'll give it a shot:

Every so often, when I'm using my Butternut vertical mounted on the
garage roof, I notice that signals are way down, like more than 20 dB
down, almost like no antenna or a shorted antenna.
Well, I discovered that if I go in the garage (where there is a
lightning arrestor installed at the 75 ohm and 50 ohm coax junction) and
disconnect the lightning arrestor and squirt some contact cleaner on the
connectors, it works fine again. This happens every few months or so.
I just bought a new lightning arrestor last month, and I took a wire
brush to all the connectors and adapters connected to it, but the
problem still keeps coming back. (It just happened last night). I guess
it's possible that one of the coax connectors has an intermittent
connection, but it didn't look that way when I put an MFJ antenna
analyzer on it. I could only check one of the connectors though.
It's not a real serious problem since it's not hard to fix
(temporarily), but I was wondering if anyone has ever heard of anything
similar and found the cause. (Static discharge of some sort maybe?)


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