[Towertalk] tnx info, Greenlee & 80M vert.
RICHARD BOYD
ke3q@msn.com
Fri, 17 Jan 2003 16:12:01 +0000
It's been less than 24 hours but I already have good suggestions on both my
questions. Here's a summary, some of which went just to me and not to the
reflector.
1. I realized myself I could ease the Greenlee hanging chad problem by
using a larger drill bit for the pilot hole. Then the chad would be less
likely to bind not only in the cup where it, by definition, is going to be
an exact fit, but also to the screw in the middle. With a larger pilot hole
it would only be binding on the outside. This occurred to me after
launching the towertalk question.
2. I like the idea of using WD-40 on the punch beforehand. I have noticed
they have a definite tendency to rust.
3. On the various ideas of prying and knocking the chad out, I will be
trying those.
4. On the 80M vertical, some have reported 2:1 SWR bandwidth of 60-80 kHz.
I suspect those are on shortened antennas. K4JA and K2YWE and maybe one or
two others report over 300 kHz 2:1 SWR bandwidth -- K4JA's with a fullsize
four-square. The broad bandwidth seems due to larger diameter radiators. A
four-square may have a larger diameter radiator effect by virtue of being
four radiators rather than just one, plus K4JA's and many others use tubing
or tower as the radiators themselves. K2AV had a nice chart of bandwidth to
be expected with various diameter radiators.
5. Many suggested more than two radials will increase efficiency with a
corresponding decrease in SWR bandwidth, that my bandwidth may be due to
needing more radials for better performance. I may try this, despite the
Dayton Antenna Forum presentation a few years ago that said even just one
radial was enough and many very successful stations using just one or two
radials, when the radiator is elevated. This strikes me as analogous to the
quad v. yagi debate and each side quotes scientific evidence to prove their
point. I think it is undisputed that more radials are better when the
vertical is ground mounted. There also seems to be at least a consensus
that elevating the feedpoint of your vertical is good and that fewer radials
are needed (e.g. N4KG's 10 and other peoples' 4) to equal the performance
with 120 radials on a ground-mounted vertical. The debate comes down to
just how few radials on an elevated radiator will equal or come close to 120
ground mounted radial performance.
Thank you all for your helpful comments and suggestions! CU on 80.
Next, pruning, maybe more radials, run the coax the rest of the way to the
house, contemplate hooking up CATV hardline that's already run most of the
way instead of RG-213 that I'll almost certainly hook up between the antenna
and shack first to have some fun with it and check it out, and some
beverages for receive. Then, get a 160M antenna up and tribander or
40-through-10-bander to get on all the bands.
73 - Rich, KE3Q
Rich Boyd
KE3Q/W3AO
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