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1-7 of 7 messages
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How can I bug-proof my Cushcraft A3 traps
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by KT8K on September 20, 2009
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I have been running the driven element from an old Cushcraft A3 for years by hanging it as a vertical dipole in the tree tops. It always worked great, though I could see some loss when it touched leaves in the warmer part of the year. Over the last couple of years it got worse, though. Signals were no longer as strong as before in comparison with my other antennas (all but one of which it used to beat). I took it down and disassembled it, and took the traps into the shack to see if I could peek inside or at least clean them out. When I pulled off the end caps I was surprised by an entire ants nest inside one of them (I ran and tossed the trap out on the patio before they got all over the shack) and the biggest spider nest I'd ever seen in another one (that also was quickly pitched outside).
With the bugs gone, I am now tapping the outer covers off the traps and cleaning out the bug nests and crud inside. My question is ... what kind of sealing can I do to prevent the bugs getting in again, while still allowing the traps to drain off condensation. Or should I just seal them up liberally with a good acrylic sealant and not worry about condensation?
I always appreciate the advice of the good folks here, and have learned a ton from many of you. Thanks for your help again.
best rx & 73 de kt8k - Tim
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RE: How can I bug-proof my Cushcraft A3 traps
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by WB2WIK on September 20, 2009
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The CC trap covers aren't part of the trap design, they're just covers (unlike Hustler verticals, for example, where the trap cover is actually one electrode of the trap capacitor so they're critical).
You might consider leaving them off altogether and just applying high voltage insulating varnish over the whole assembly (once it's been very well cleaned) instead.
GC (General Cement) makes a few coatings that are perfect for this: They brush on, they're cheap, they're very UV-tolerant and very good high voltage dielectrics.
WB2WIK/6
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RE: How can I bug-proof my Cushcraft A3 traps
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by KT8K on September 20, 2009
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Thanks, Steve. I wasn't sure so I put the covers back on. It had been more than a month since I thought I got all the bugs out, but when I disassembled one of the 15m traps I got another multi-dozen ants in the shack. Fortunately I had the vacuum at hand ...
Leaving off the covers and coating the assembly sounds like a great idea, but I wonder if the covers don't add some to the overall strength of the element. I am considering going the acrylic caulk route and just "hermetically" sealing the traps this time. I have the caulk, and the day job has left far too little time for antenna work recently - this might be the last good chance to work on this one as the sun is setting much earlier, I have others to put up, and the big horizontal loop must be fixed in my scarce weekend hours between now and the big contests.
Incidentally, I was able to tap out the trap insulators using an old Cushcraft 1/4 wave 2m whip. It's pretty stiff, and I was able to slide it up inside the covers and pop the insulators out (1 each on the 10m traps and 2 each on the 15m traps) by tapping the exposed whip end gently but persistently on the concrete patio. It's good to do this outside, as it's amazing how much crud and crap builds up inside those traps over a decade or two, especially when they're suspended from a tree and ants and other critters are using the ropes as a super highway to the ground. I certainly know why replacing the coax last spring didn't help - the source of loss was inside the traps.
I may insulate the rope from the antenna this time, too, as I was always concerned about extra loss when the polyester rope was saturated with water or covered in ice and potentially shorting around the traps. In the past I just tied the rope to the U=bolt at the center of the element and then attached it to the bottom of the dipole with a stainless steel hose clamp to keep the thing roughly vertical. This also allows me to pull the center point of the antenna up to the branch and let the driven side of the dipole stick up well above the supporting tree branch. Does anyone think insulating the rope from the dipole will make much difference?
My fan dipole may work great at 60', but when the band is coming in or going out and the low radiation angles predominate this vertical dipole (also fed at about 60') can be more than an S-unit better. Normally the two are about the same except in a couple of directions favored by the fan dipole.
Thanks again & best rx to all de kt8k - Tim
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RE: How can I bug-proof my Cushcraft A3 traps
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by WB2WIK on September 20, 2009
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I would not use any kind of caulking for this.
Here's something that works well for this application (scroll down to "Red-X Corona Dope"):
http://www.gcelectronics.com/order/SubCatPDF/thinners%20Solvents%20Coatings%2055-56.pdf
It's weatherproof, strong, dries to a hard finish, and is very good around high voltage.
WB2WIK/6
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RE: How can I bug-proof my Cushcraft A3 traps
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by N2OUV on November 2, 2009
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Hi Tim,
Im a bit late to your post but have had similar experiences with bugs in the traps on my A3S.
What I did was clean the outside of the trap cover with scotch brite. I then bought some fiberglass screening and cut small squares to go over each drain hole with and inch or two overlap. I glued each piece of screen in place with 5 minute epoxy. The best way is place the screen on the trap cover and put the epoxy over the screening that way its embedded in the epoxy. Just dont block the hole with epoxy. Mine has been up like this for 11 years and no problems.
73 es gud luck.
Joe
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RE: How can I bug-proof my Cushcraft A3 traps
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by N1LO on November 3, 2009
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Great tip Joe,
I think you could accomplish the same thing in stainless steel mesh using replacement faucet aereator screens.
--...MARK_N1LO...--
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RE: How can I bug-proof my Cushcraft A3 traps
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by K8SOR on November 3, 2009
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Something you might try. In the spring, just when the days are getting warmer, I find ants starting a colony in my mailbox. I just toss in a few moth balls, or crystals. It usually takes care of all the bugs. At out camp, I put them in the breaker box (outside-raintight) and don't have a problem with the wasps, ants or any bugs. You might try this, they usually last all year.
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