Hi Stan,
From a mechanical engineering standpoint, let me point out a few things
that may help you keep on the right track in your persuit of proper
tensioning.
>For those of you who either own one or have the literature, you can see
that
>it does not measure tension in the cable directly. Rather, it measures the
>diffculty involved in putting a slight kink in the cable.
You are not exactly correct here. This is called "deflection measurement",
there is no "kinking" involved. It simply measures how much force is
required to move the cable a given distance perpendicular to its own axis.
>This will be
>proportional to the tension in the cable, and, if done correctly, can give
>you an idea of what the tension in the cable is.
You are, of course, right on the money here, it will give you a good "idea"
of the tension. Most hams just want to know if their guys are all tensioned
the SAME as each other, so they will probably be happy to just have a number
to compare from guy to guy.
> Anyone who has worked with
>EHS cable and the more flexible wire rope knows there is a great deal of
>difference in how hard it is to kink EHS cable as compared to wire rope.
This is not exactly correct. It is natural to think as you do, that the
stiffness of the material in a "free state" (meaning 'not under tension')
will have a bearing on the guage reading, and it will. However, the variance
between EHS and wire rope will be much less than you think. This is because
as you increase the amount of tension in the guy it becomes "stiffer" and
the resistance to deflection due to material stiffness becomes statisticly
smaller as the tension increases because the tension is exerting more
resistance (to deflection) than the material stiffness. As the tension in a
piece of EHS and a piece of wire rope increase their guage readings will
come closer and closer together until they are nearly the same at the yeild
(breaking) point. The real question is, how much do those readings vary at
the start, with just reasonable tension.
> He said that he believed Loos tension
>guages could be used with with EHS wire but they would have to be
calibrated
>specifically for it. In other words, the calibration charts supplied with
>the Loos guage are not for use with EHS cable.
You are correct here also.
>So it looks like what needs to be done is a calibration chart needs to be
>made by someone who has an accurate dynomometer, a Loos tension guage, and
a
>few towers with various types and sizes of guy wire. Without doing that,
it
>looks like we are back to guessing . . . Here is my guess. I would guess
>that a Loos tension guage calibrated for 1 X 19 sailboat rigging will be
>fairly close when used on wire rope of the same outside diameter but not
>very close when used with EHS cable of the same outside diameter.
I wouldn't be too sure of this. Better do some field research.
> I don't know the
>answer to this question and maybe someone out there who does know could
>tell us?
I'm not a PE, but I do have many metalurgy, strength of materials, and
mechanical engineering courses under my belt, in addition to 22 years in the
mechanical field. I believe that the loos guage will give the average ham
good COMPARTIVE results on most cable types. For those who need EXACT
numbers, you should probably find an engineer. There are many factors
involved. Good luck and be safe.
Tom Lindtveit N2GQS
Tom@utd.com
>From Bob Selbrede <w9nq@ccis.com> Sat Apr 27 02:46:08 1996
From: Bob Selbrede <w9nq@ccis.com> (Bob Selbrede)
Subject: WPX CW in the U.K.
Message-ID: <199604270146.AA01882@bart.ccis.com>
Hi All,
I will be traveling to London for business, from Dayton, on May 19th
and would be interested in doing the WPX CW contest on 25-26 May from
somewhere in the U.K before heading home. Are there any Multi-Singles or
Multi-Multi's being planned in or around London? Would anyone in the London
area allow me to use their club or home station for the contest? I would
also consider traveling to GM, GW, ON, PA, etc. Any help would be
appreciated. Please reply to my home E-Mail address (this one). Thanks!
73, Bob W9NQ
w9nq@ccis.com
>From John Brosnahan <broz@csn.net> Sat Apr 27 04:34:18 1996
From: John Brosnahan <broz@csn.net> (John Brosnahan)
Subject: precip static: hints
Message-ID: <199604270334.VAA21083@lynx.csn.net>
Douglas Zwiebel <KR2Q@worldnet.att.net>
>
>1) SNOW static is just as bad a rain static...not much LIGHTNING in snow!
In general I agree with you, but one of my worst
electrical storms of all time was during an incredible
blizzard Sunday afternoon in ARRL DX a few years ago.
Lightning everywhere, insulators were arcing over, and we
(W0UA and myself) bailed out of the shack--without disconnecting
anything or turning anything off--just too dangerous. It lasted
for a 1/2 hour and the snow that continued after the electrical
storm was well charged and very noisy. We just had some
lightning a few weeks ago during a snow storm. Our spring
rains are often in the form of snow. Mar/Apr/May are our
snowiest months out on the eastern plains of Colorado and are
sometimes accompanied by serious electrical activity.
In general I would say that half of our snow on the plains
NE of Denver is noisy and half is pretty quiet when there is
no serious electrical activity.
Hugh charges can build up even in clear air and there
is often as much as 300 volts per meter without electrical
activity in the form of lightning. This means that a
50 meter tower can have a potential of 15,000 volts
from the top to ground, which makes a very good
case for using shorted 1/4 stubs on things like
slopers.
When I first got my novice in 59 I used to be kept awake
by the arcing PL-259 on the 40M Flat Vee dipole at 20 ft, even
when storms were not visible when going outside. Not much
current involved but certainly enough to destroy solid state
devices.
I was repairing a 1.5 to 30 MHz Log Periodic Ionospheric
Sounder antenna once and had disconnected the 20,000 ft
of wire from ground while installing a new balun. Knowing
the potential for potential I tried to keep away from the
"floating" wires. Even though I was wearing rubber
shoes the antenna still "reached out" and knock me
down from the charge buildup. Must have jumped close
to a foot! It was a clear day but dry and with a 10 mph
wind.
I was also on top of a 330 ft tower once, counting the
number of bolts that had fallen out due its location
next to the vibrator that picked up fully-loaded railroad
cars and shook out the coal for the power plant, and the
lightning rod had a 6 or 8 inch flame of corona coming
off the top. It was an absolutely clear day with no wind.
Point is that there can be large charges built up on
ungrounded elements, even when there is no electrical
activity in the area. I ALWAYS ground all of my elements.
When lightning storms pass over the house they stop
lightning in most cases for about 600 ft on both sides
of the house due to the charge drainage by all of the
well-grounded towers and antennas. Now the lightning
doesn't strike the house or towers but nails the barn that
is actually in a hole and about 600 ft away!
My experience with two 4L 40 M Yagis that are stacked
at 80 and 160 ft (then--they are a little higher now) is that
the lower one is "shielded" by the upper one which
drains off most of the charge. Another 4L 40M beam at 80
ft on a separate tower that is not shielded by higher antennas
is often quite noisy--much more so than the shielded one
at the same height.
I also detect huge amounts of noise being generated by
arcing across the insulators in the guys on the stack. The
stacked Yagis are very noisy and non directional to the
noise, whereas the separate 40M Yagi peaks up on the noise
when pointed at the stack.
Not an answer but some more data points for a rigorous
analysis of the effect.
GROUND EVERYTHING
73 John W0UN
John Brosnahan
La Salle Research Corp 24115 WCR 40 La Salle, CO 80645 USA
voice 970-284-6602 fax 970-284-0979 email broz@csn.net
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