W8JITom@aol.com wrote:
>To my knowlege, no one has ever done an experiment proving charged rain drops
>are the source of the problem, and that insulation helps this and not a
>corona problem. I'd be willing to bet the "rain drop discharge" is folklore,
>and the real problem is corona discharge.
Tom
There is an Junior High School science project that I remember performing
(A long long time ago) that dripped water through a coil of wire. The coil
in turn was hooked to a very sensitive meter movement or oscilliscope
which flickered every time a drop of water passed through the coil.
The inference was that the water drop was indeed charged. The "moving"
electric field caused by the falling "charged" drop in turn induced
a current in the coil which in turn was detectable on the meter or scope.
Been there, did that.
Rain drop discharge or corona discharge? Which came first the chicken
or the egg? Just remember that a chicken is an eggs way of being sure
there will always be more egss. I suspect that BOTH are at work here
and in fact the charged rain drop may well be the corona's egg ( or is
that chicken?).
Anyway I do agree with your comments about insulated wires etc. In
fact it is just as likely that a charged drop falling on an insulated
wire will transfer its "static" charge to the insulation which at
that point might be considered part of a capacitor which would couple
the noise into the antenna system anyway.
It maybe that a "Radome" approach is the only way to avoid the problem.
i.e. put your whole antenna system under a giant dome! That oughta
give some of the big guns who have everything something to think about!
Imagine being to climb your tower in safety, 24 hours a day, regardless
of what the weather is outside! No rain static, no snow static, no
corona discharge....Life is beautiful...I like my room... my room is soft,
maybe even inflatable (like those indoor golf driving ranges)~8^).
Dave
N0DH/7
n0dh@comtch.iea.com
>From Ward Silver <hwardsil@wolfenet.com> Mon Apr 29 17:48:18 1996
From: Ward Silver <hwardsil@wolfenet.com> (Ward Silver)
Subject: Rain Static
Message-ID: <Pine.OSF.3.93.960429094218.9675M-100000@gonzo.wolfenet.com>
The sense that I'm getting is that it's a single "perceived" problem made
of up at least two sub-problems.
First of all, there's the all-the-time, ongoing corona discharge, however
slight, of the continuous earth/air charge transfer process. Due to
changes in the potential difference during storms, this noise source
increases in intensity during storms, even if there's no precip at all.
Second, there's the noise cause by drops or flakes with a charge hitting
the grounded element. The intensity of this source isn't really well
defined, nor is the process all that well understood.
Third is a mixed bag associated with whether or not there's a DC path to
ground from the antenna, whether the wind is blowing, how large the
antenna is, how tall it is, whether there are adjacent antennas, etc.
If I had to call it today, I'd take W0UN's advice and ground everything,
and then try to place a tall mast above any high antenna to try and move
the corona discharge point as far away from the antenna itself as
possible. The insulation issue is probably not very important. If I get
a chance, I'll browse the IRE/IEEE indices for stuff on precip and
atmospheric static.
73, Ward N0AX
>From w7ni@teleport.com (Stan Griffiths) Mon Apr 29 18:15:40 1996
From: w7ni@teleport.com (Stan Griffiths) (Stan Griffiths)
Subject: Rain Static
Message-ID: <199604291715.KAA00731@desiree.teleport.com>
>
>On Fri, 26 Apr 1996, De Syam wrote:
>
>> 1) The severity of the precip static is not proportional to the amount of
>> rainfall, but appears to be associated with the propensity of the storm
>> to contain lightning.
>
>This would probably indicate that the raindrops carry a charge which
>varies considerably based on the cloud's internal charging "engine". So
>we could have "noisy" storms and "quiet" storms. This certainly squares
>with my Seattle vs. Midwest experiences. Out here we consider lightning
>to be rare. I hear maybe a dozen strikes a year and they're never of the
>intensity I observed in Missouri. My rain static now is minimal compared
>to what I had to deal with during thunderstorm season in the Midwest.
Here is another theory: It has been noted that "high" antennas seem to be
more susceptable than "low" ones. It has been suggested that the drops are
discharged by the upper antenna in a stack and therefore have little or no
energy left to discharge into the lower one. (This does not seem likley to
me.) It has also been observed by someone in an earlier post that his lower
antenna on a separate tower does not get rain static as bad as his high
antenna. Could it be that the potential difference between a particular
charged drop and the antenna is a function of the antenna's height above
ground? Maybe the antenna itself is charged under these conditions and more
highly charged further above ground? Maybe drops lose their charge as they
fall and if they hit an element at 100 feet above ground the effect is far
greater than if they hit the same element at 50 feet above ground?
>> 2) The precip static is never a problem with my quad antenna.
>
>Ditto at my QTH. Maybe rain static comes mostly from raindrops hitting
>the ends of the elements, which are pretty high impedance. The quad has
>high-impedance points, too, but are they as high as the open ends of
>tubing? Maybe insulating just the ends of the elements would be helpful.
Theory: Maybe we are seeing that the actual cross-sectional area of the
quad elements, which are wire, is far less than normal Yagi aluminum tubing
elements. Quad elements simply intercept fewer drops?
>> 3) Precip static is often noted even when there is no rain falling, but
>> when there is a thunderstorm in the area.
Theory: There might still be charged "drops" there but very small ones,
more like fog droplets.
>I guess each little "splat" could radiate some energy at RF as the charge
>transfers to ground. Do we have any atmospheric physicists on the
>reflector? Sounds like a great thesis, "A Study of Rain Static as
>Observed at Several Harmonically Related Frequencies Across the HF
>Spectrum."
>
>73, Ward N0AX
These are only my wild guesses. I have no credentials to make me an expert.
Stan w7ni@teleport.com
>From w7ni@teleport.com (Stan Griffiths) Mon Apr 29 18:15:56 1996
From: w7ni@teleport.com (Stan Griffiths) (Stan Griffiths)
Subject: Loos Tension Guage
Message-ID: <199604291715.KAA00911@desiree.teleport.com>
>
>
>>So what do the power companies, telephone companies, and CATV companies do
>>to measure the tension in their guys and support cables? I don't know the
>>answer to this question and maybe someone out there who does know could
>tell
>>us?
>>
>>Stan w7ni@teleport.com
>>Aloha, OR
>
>==========================
>
>Stan,
>
>I have a crew of technicians that do tower maintenance for towers used in
>Public Safety communciations. The towers they maintain and inspect range in
>size from 100 ft to 450 ft and EHS guy sizes from 1/2 to 9/16 inch. They use
>a tension gauge manufactured by Penn-Tech Intl. Inc. out of West Chester,
>PA. tel (215) 692-4436. I bought the two we have back in 1993 and from
>what I remember the cost then was approx $1,200 each. They are NOT cheap,
>and I have used one on the guys at the W0SD station towers and they are very
>easy and fast to use. Just place the guy wire between the two hooks and
>move the handle down which in turn moves a center piece that pushes against
>the guy to measure the tension, read the gauge, and obtain the resultant
>tension in pounds from the calibration charts for the particular guy size in
>question. Perform this 3 times on each guy wire and take an average. Very
>similar to the Loos gauge in operation, it appears. However, it is
>designed ONLY for EHS. I have not personally compared the results of this
>with the dynamometer setup we also have, but from what I have seen on the
>results from my field technicians the two methods compare very closely. This
>is certainly an item that is out of my price range, but sure seems well
>worth the money as far as quality and ease of use. . Can't tell you what
>the other organizations use that you mention above. Hope this helps.
>
>73, Todd
>WD0T
>
>toddd@dci.state.sd.us
Hi Todd,
Thanks for the info. It seems to confirm my suspicion that all these clamp
on tension measuring devices need to be calibrated for the specific cable
they are being used with. I have also found another source of similar
devices and I have not yet had a chance to make some inquiring phone calls.
There is a company called "CESCO" (Communications Equipment and Service
Corporation) in Powell, Ohio that puts out a catalog with all sorts of
professional tower worker tools in it including two kinds of tension
measuring instruments. One is a model TM-750 that sounds like what your
crew has and another is a "Tension Load Cell" that is a "in series" type
device with a 5 ton capacity. You could call 1-800-642-7698 to get a
catalog from CESCO. They might get upset since this is their "order line"
and tell you to call back on (614) 846-4733.
Stan w7ni@teleport.com
Aloha, OR
>From w7ni@teleport.com (Stan Griffiths) Mon Apr 29 18:16:10 1996
From: w7ni@teleport.com (Stan Griffiths) (Stan Griffiths)
Subject: Loos Tension Guage
Message-ID: <199604291716.KAA01047@desiree.teleport.com>
>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.
Hi Tom,
Thanks for taking the time to respond to my post.
>>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 looks like a poor choice of words on my part. I guess a "kink" would
probably be a permanent bend in the cable. I meant a temportary bend in the
cable.
> >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.
This is an interesting point. If you assumed a tower with only one set of
three guys at the top and you tensioned only one of them, it appears to me
that the tower top would move such that the tension in all three would be
equal, assuming all the guys are spaced equally around the tower and equally
distant from the base. It would further seem that a second set of guys
might put a slight bend in the tower as you tension one guy to the required
amount, but again, the tension would be equal in all three at one level.
You could then let out on one and tighten up on another guy to bring the
tower back to vertical without a bend at the same time maintaining the
correct tension on the guys.
You say that most hams want to know that all their guys have the SAME
tension. I assume you mean the tension in the upper sets is equal to the
tension in the lower sets. I am not even sure that is desirable. It is not
obvious to me that guys at different levels SHOULD have equal tension. I
notice in some of Rohn's guying charts, they suggest that the top set of
guys needs to be of heavier cable than lower sets. This would imply to me
that the top set should be under greater tension than the lower sets . . .
> > 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.
Yes, I agree with that.
>> 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.
Well, we certianly agree that guessing on this stuff is NOT the way to do
it! I am trying to get enough stuff together to actually run some field
experinments. If I do, I will share the results here.
Stan w7ni@teleport.com
>From David Clemons <dave@egh.com> Mon Apr 29 18:05:42 1996
From: David Clemons <dave@egh.com> (David Clemons)
Subject: k1ea/k1ar conspiracy
Message-ID: <Pine.3.89.9604291316.B19211-0100000@newman.egh.com>
Hi all,
Thanks all for clearing up the reason(s) for why K1EA/K1AR do so well.
Now I have a simple little math formula which clearly explains it, and an
old theory debunked (...because they were loud...). No one will ever believe
what I used to attribute their scores to! (I used to think they were good.)
73, Dave Clemons K1VUT
>From Rus Healy <rhealy@mdsroc.com> Mon Apr 29 19:01:09 1996
From: Rus Healy <rhealy@mdsroc.com> (Rus Healy)
Subject: CATV Hardline connectors
Message-ID: <Pine.LNX.3.91.960429134805.3912C-100000@mdsroc.com>
Okay, everyone has their own "best" way of doing this. Mine is to use the
real CATV terminations. They're cheap (about $7 each in 1993 for 1/2-inch
cable), weathertight, and *designed for the application*. Their true
beauty is that their outer threads accept a stock N connector--female or
male. So you cut back the long center pin of the CATV termination, solder
on the N connector center pin, thread the connector bodies together, and
check the center-pin length. Remove the connector body and adjust the
center-pin position as necessary. No damage results from repeated assembly
and disassembly.
As someone recently mentioned here, N connectors are *the* way to go for
Amateur Radio applications from the electrical performance and
ease-of-assembly standpoints--but they can't be had for $1 each like
PL-259s can. Still, I'd opt for this avenue, coupled with a $5 (at Dayton
prices) N-to-UHF adapter any day of the week. There is one other factor:
You need to have access to a coring tool for the size of cable you're
using (or a lot of patience) to install the CATV connectors on the cable.
The coring tools can be had for around $35. Considering the number of
hardline runs most of us have (or want), even this extra cost is a
bargain.
--73, Rus
-------------------
Rus Healy, NJ2L
nj2l@mdsroc.com
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