[Boatanchors] antenna question

[Gary Peterson]

“Assuming it is something inside the trap..    I am planning on taking the tower off the carport and ground mounting it soon..
what's the process for fixing the trap?    I've heard the plastic end caps can slide off ...  do I just take them off and flush out
the trap with water or is there some other thing I should do?
RAY FRIESS”

I have rebuilt many, used Hy-Gain, Mosley and Cushcraft beams and trapped verticals with good success.  Some were rebuilt because they did not work properly or were intermittent.

First, mark every junction with a Sharpie.  The marks will allow you to re-assemble with the proper mating pieces and with proper lengths.  I make a line on the smaller tubing, at the junction where it slides into larger tubing and then mark the two sides of the junction as A and A, B and B, etc.  I disconnect every junction and apply a bit of aluminum joint compound to the inside of every tube and the outside of tubes that slide inside larger tubes.  Aluminum joint compound is used by electricians to avoid high resistance connections involving aluminum-aluminum and aluminum with other metals, such as copper.  The three brands I am familiar with are No-Al-Ox, Ox-Guard and Penetrox.  These are available at Ace Hardware stores, in the electrical department, and electrical jobbers.  Aluminum is very chemically active and quickly forms a very thin, almost invisible oxide which is a good insulator (think of the dielectric in an electrolytic capacitor).  The joint compound prevents oxidation while the metal is cleaned.  On the outer parts of tubing, I use emery cloth to remove the oxidation, while the joint compound prevents air from re-oxidizing the metal.  On the inside of the mating tubing, I use a round wire brush, available in hardware store plumbing departments.  The joint compound protects the aluminum from further oxidation as you ream the corrosion out.  As soon as you get both ends of a junction clean, re-assemble and insert/tighten self-tapping metal screws or tubing clamps.  I even put a little joint compound in the screw holes.  Do not remove the excess joint compound.  The joint compound will make it much easier to disassemble the antenna in the future, as it is a mixture of silicone grease and powdered zinc.

Carefully disassemble each trap.  Remove any detritus (i.e., spider nests, dead bugs, etc.).  You will, typically, find aluminum wire wound on a plastic bobbin.  At every junction, clean the aluminum wire where it wraps around a self-tapping screw and the metal surface to which it is attached.  Again, use joint compound and emery cloth to get everything shiny before re-attaching.  Use joint compound and abrasive on every metal to metal junction in the entire antenna.  When finished, you should, pretty much, see continuity across every junction with an ohmmeter.  You may need test prods with sharp points and use a bit of force to “stab through” the aluminum oxide that has formed on the outside of the antenna elements.  If it’s a Yagi, don’t forget to make sure the trap drain holes are open and facing down.  Replace any deteriorated trap end caps and corroded hardware.  Stainless steel hardware should be assembled with anti-seize compound, available at auto parts stores.

I hope that helps and let us know how your project works out.  73,

Gary, KØCX