Summary: TH5/TH6 traps
TSkelton at engineer.clemsonsc.NCR.COM
Tue Apr 13 15:03:00 EDT 1993
Thanks to everyone for all the responses concerning my request
for information on traps used on the HyGain TH5/TH6 series of
antennas. I was absolutely stunned at the number of you who
took the time to respond.
Over the weekend, there was a note on our local Packetcluster
from Tom/N4KG regarding maintenance of tribander traps. In my
haste, I almost didn't read it except that I have learned that when
KG posts something it is worth reading. Anyhow, Tom related how
he thought he had a problem with one of his tribanders (a TH3)
that was 6 dB down from a TH7 at the same height and was suffering
in overall performance. (The light almost clicked on in my thick
skull) He described how he slipped off the trap cover (Al Kaplan at
HyGain said I can't do this) and re-tightened the self-tapping screw
that holds the trap cover ("C" in the "LC") in place. Voila!! His
problem was fixed.
Hmmm....well, if it is a self-tapping screw
(i.e., not a rivet) why can't I remove it and see what's inside? I
had nothing to lose except being forced to buy a replacement trap.
I previously didn't look closely enough to see that if the plastic trap
end is slid out slightly, you could see this 1/4" screw head. So, I
moved the end cap and removed the screw. I then carefully slipped
off the other end cap --- this was on a 10m trap that had been removed
from the driven element. Inside I saw a clean, dry, non-damaged and
beautifully wound 10m coil on a plastic form. I then opened the 15 m
trap and saw basically the same thing except that the coil looked like
it was covered in a layer of pollen. At this point, I was feeling as if
maybe my traps weren't the real culprit (the light clicks on in my
Later in the weekend, after countless fun family projects, honeydoos,
etc., I had time to sit down in the doctor's office with my sick
daughter and start the April issue of QST. The article, to which
others had referred, on antenna corrosion was read first. (the light
is getting brighter) The antenna in question (TH5 -- old version, not
dual driven elements) is at least 10 years old, and does not have
stainless steel hardware. Also, it has been taken down and re-
assembled and moved at least 6 times.
In order to get moving on this antenna re-building project before
The Second Coming, I started by mounting on the boom on a support
about 5 feet above ground. I then got the 10 meter reflector and first
director elements and disassembled them (after wrenching and
breaking the severely rusted clamps holding them together).
What I saw immediately made a lot of sense: tons of built-up
oxide on the inside of the elements (the light is now so bright it
is about to blow).
So, maybe my problem was not the coax that I replaced or the
trap that I thought I had blown. Maybe the arc in the SB220 was
just one of the parasitics that I haven't quite fixed. I still don't
know why the SWR got so bad (4:1) under a heavy downpour;
maybe the other trap (15m driven element) I haven't looked at
will be bad.
Regardless, based on the input from this reflector, the QST
article, N4KG's advice, and my lack of funds (to the guy who
said $75 is not a lot of money considering how much a new
antenna costs...ur right -- I just don't have $$$ to waste) I am
now happily re-building the antenna. I have an unopened
pack of "Butter-its-Not" from one of my HF6V's that I'll use on
each aluminum joint.
This headache started when I almost didn't work Romeo from
XY0RR due to the antenna problem, and hopefully will end
before Romeo shows from 5A (one of last few needed on CW).
So, if you want an antenna to work for a long time,
and not fail at a critical time like having W4MWT tell you YA0RR's
5x7 on 15 SSB and you hear him 5x1) put it up in the first place to
last. That means:
1. protective goop (NoAlOx, Butter-its-Not, OxGard...etc...others
listed in QST article) on each aluminum joint
2. cover every electrical connection (coax, balun, etc.) with high
quality EXPENSIVE (cheap in the long run!) Scotch 33 or similar
3. be careful if you use some sealants -- one guy found what he
used to be conductive!
I have also learned:
1. if something is put together by a human (like a HyGain trap),
it can be taken apart and re-assembled by a human
2. haste in putting up an antenna (I hate to admit I used some
hamfest special tape the first time I put the antenna up at the
new QTH as I thought this would be a temporary installation)
will cause pain later -- take your time and use quality components
3. advice is what you pay for it and is worth to the giver based
on the size of the invoice
4. this reflector has some smart and helpful folks.
Sorry this was so long.....thanks again. 73, Tom WB4IUX
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