[TowerTalk] Tapered elements.

[k3hx at juno.com]

OM Tom,

Lots of good advice regarding the use of Scitchbrite and an aluminum-bearing joint compound.

I've just now finished getting my trap rotary dipole (modified from the reflector section of a TH-3) back together and would like to add a bit to the discussion.

Assuming you have a new antenna, wipe the joints down with 91% isopropyl (rubbing) alcohol before using the Penetrox.  

If your antenna uses "hose clamps" to cinch the sections together, toss into the trash the ones that came with it unless you can verify they are all stainless. The worm gear screw and housing are frequently made of ordinary, plated steel. Replace with "All Stainless (a trade name) or Breeze (another trade name.)  Both are US companies who make
their hose clamps from 100% stainless.  Prepare to pay a multiple of what a cheapie clamp costs but you will be spared much frustration when you have to service the antenna.  (I learned this the hard way...HI!) You may have to go to a smaller hardware store to get these or a place that cares about doing a good job repairing automobiles.  Perhaps some of the good folk on the list can recommend a mail-order house.  I've the good fortune of having an old-time hardware store within walking distance which carries the good stuff.

After you get the antenna together, wipe the whole thing down with 91% 
isopropyl alcohol and give the antenna (except the coax connector) a coat of liquid automobile wax.  I've found this technique keeps the antenna shiny for several years.

I prefer to use a synthetic grease to "flood" the coax connection.  If you use the rubber tape sealing method, the synthetic grease will not attack the rubber tape as the carrier in joint compound might.  This material is available at Radio Schlock and is just fine.....used it in
my antenna business for many years.  I've had bad luck with "Coax-Seal"
as it tends to harden after several years.  

You may wish to swap out the mast-to-boom bolts if they are not stainless steel.  In any event, use some anti-seize compound (not the same as the joint compound) on the bolts to make servicing easier.  You can get a small amount of anti-seize compound at your auto supply store.  It comes in essentially 3 "flavors" Nickel-bearing, Copper-bearing and Zinc-bearing.  Any of these will do fine.  I tend towards copper-bearing.

Hope to see you in the ARRL 10 meter contest this weekend.

72,

Tim



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