Summer Season SafetyBy Jack L. Stone, Publisher
Nothing is too high for the
daring of mortals; we storm Heaven itself in our folly.
—Horace (65-8 B.C.)
Summer Season Safety
By Jack L. Stone, Publisher
INTRODUCTION
very season brings about its own collection of hazards. For the antenna
experimenter and user, summer is the season of very high electrical activity in the
atmosphere, otherwise known as thunderstorms and lightning. So you will forgive me if I
wish to assure myself that every antenneX reader is still with us in the autumn, complete
with family, home, and radio equipment. Thus, I venture forth a few reminders about
safety.
There are many radio services that must run in all kinds of weather. Commercial services
ranging from AM, FM, and TV all serve as long as they have power. Service industries, such
as cellular and other GHz enterprises all have subscribers that need them. Police, fire,
and other emergency services need to be one the air regardless of conditions. All of these
broadcast and communications services have—or should have—elaborate lightning
and other safety measures integrated into their antenna and equipment systems. These
systems involved engineered components tailored to the specific antenna or repeating
station site. The components protect against direct strikes, as well as surges and static
charge build-up. The general idea is to keep the entire installation at as close to a zero
voltage differential relative to the frequencies at which lightning and related phenomena
occur. Maximum protection comes at a price that requires commercial, government, or
military budgets to cover. (From here on, whenever I mention commercial service, I am
including those government and military services that absolutely must be available
regardless of conditions.)
Very few non-commercial services can afford the cost of a fully professional protection
system. Of course, very few non-commercial services need to be available during the worst
of summer’s electrical weather. Most amateur repeater stations stay on the air as a
public service. They often continue to function when police, fire, and other services go
down. A number of amateur repeater stations have received the full protection treatment.
Others get by on partial treatments or simple luck.
The individual antenna owner rarely has access to full professional-level protection. In
fact, the individual antenna user either does nothing for personal protection—or he
or she creates an imitation of a professional protection system and falsely believes that
it will perform like the system used by the local broadcast antennas. Now let’s add
in the usually amount of carelessness, and we have a formula for danger and damage. The
damage may range from fried solid-state components in expensive equipment all the way to
homes that turn into embers and ashes.
No individual amateur radio operator, short-wave listener, or antenna experimenter ever
needs to be “on the air” with an active outdoor antenna during an electrical
storm. Therefore, the first line of defense against damage from electrical storms has two
steps. First, disconnect the outdoor antenna leads from the equipment. Second, ground all
antenna leads to a deep ground rod out of doors as far away from the home as may be
feasible.
Not all damage from electrical storms comes from direct lightning strikes. Nearby strikes
may induce energy surges into antennas, leads, and even telephone and electrical wiring.
To protect against such surges, many newer homes have surge protection at the main
electrical box. (If you main-box surge protection is from the early days, you might have
it checked to see if it is still working or whether you need to upgrade the protection.)
In addition, many folks use surge-protection “strip” outlets for additional
protection against high-energy charges that may get through the main-box protector.
Although some say that we do not need the additional protection if we are using the latest
generation of main-panel protection devices, the added layers of protection do not hurt.
An older rule of thumb said that the higher the capacity of a surge-protection device, the
slower it was to react. Therefore, the smaller strips served a good function, with their
faster response time.
SAFER WAYS
Perhaps the safest system available for the individual antenna user is to perform a total
disconnect of sensitive devices from all external sources of surges that might come from
electrical storms. For the amateur radio operator, that means disconnecting all antenna
feedlines, all ground lines, and all AC power lines, leaving the equipment isolated, as if
it had not yet been installed. Equivalent disconnections are possible for short-wave
receivers, unnecessary television sets, computers, and sound systems. All such devices are
susceptible to surges that may enter via ground lines. Most solid-state equipment does not
care whether a high over-voltage occurs on the groundside, relative to inert devices, or
on the normally energized side (or Vcc side) of the system. The voltage differential can
do equivalent damage. The most total disconnect possible is the safest way to preserve the
expensive equipment.
One of the most illusory devices available to antenna users is the gap spark arrestor. One
may still buy gap lightning arrestors in their old form of two plates with points near to
each other. Modern equivalents often employ spark plugs. In either case, a strike or even
a very heavy charge build-up may ionize the air between the terminals of the gap and
provide a show to anyone watching. Once the ionized path exists, most of the current can
indeed proceed down to ground—assuming that the device is correctly installed.
However, for a small fraction of a second, while the path is forming, the energy is
propagating down the antenna lead to the equipment and the home. That time was once enough
to protect relatively insensitive vacuum tube devices. However, it may not protect
solid-state gear at all. Yet, once individual install gap lightning arrestors, they simply
assume that everything is safe, including their equipment, home, and family.
The field of protection from electrical energy thrown around so liberally by Mother Nature
in summer is fraught with vagaries, lack of full agreement, and downright commercialism in
the attempt to sell devices and services. Although we are learning more about the behavior
of lightning every day, we are also learning that caveat emptor still rules the market
place. So in the end, all that I can do is make a final plea:
Please give yourself, your family, your home, and your equipment the maximum safety margin
that you can. Be alert to prospective and approaching storms. Take all of the
counter-measures that you can to ensure electrical safety. Always err on the conservative
side of the ledger when it comes to electrical energy in its most violent natural form.
If you happen to live in the southern hemisphere when you read these notes, please save
them and re-read them in November or thereabouts. Those of us in the Northern hemisphere
will be worrying then about ice and snow on our antennas.
We may not be able to do much about hurricanes, typhoons, and cyclones (depending on where
you live), but we can all do a better job of protecting ourselves from both the lesser and
the greater evils of lightning.
To read more details about what to do to help minimize damages from lightning strikes, we have some excellent articles in the past issue archives on lightening protection by Tom Cox, KT9OM.
EMAIL SAFETY
Folks
should now beware of the latest trick being used on an increasing scale by the email
spammers. As the filtering software gets more sophisticated at detecting spam and other
junk mail, the spammers must devise new ways of avoiding or fooling those filters to get
the spam through to you.
The latest trick is the use of images rather than text in the spam messages. Those images can fool some filters because there is no easy way of detecting if such an image file is just an innocent picture or a pitch to sell something. At first, the spam-fighting filters were able to analyze the code used for the images and found they had a common "fingerprint" and could flag it as junk. Thus, the images needed some other way of disguising its code. They did so by finding a way to make each image vary as to color, borders, etc. which altered the fingerprint each time and so, no longer a constant for the filters to identify.
It has been reported that such revised image-spam attacks have increased by 40% within just the past couple of months. Image-type spam now accounts for about 15% of all spam.
Even worse for users, the image-spams are nearly 10 times larger than regular text spam and will heavily burden the mail servers and the user downloads. Those with limits on mailbox space will hit those limits all the quicker.
The good news is that we have some very capable people working on new filters sophisticated enough to deal with this new threat. Then, it will once again be up to the spammers to design some new trick—and the fight continues!
Always be careful on what you click! Stay safe!
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Along with the continuing fight against spam/virii junk, protecting our material and valuable bandwidth against piracy takes up a great amount of our time—time we can't really spare. The Internet is simply not the friendly neighborhood it used to be in the "old days" and more and more security must be installed to counteract these intruders. Thus, we have made the access to the Guest Rooms as automatic as possible for you to manage your own login.
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AN INVITATION TO CONTRIBUTORS
antenneX thrives
on the contributions of antenna experimenters, ranging from the informal home shop
construction project to the theoretical investigation of basic antenna, feedline, and
propagation phenomena. Over the years, we have published articles on the use of new or
newly adapted materials, known antennas adapted to new circumstances, modifications of
antenna structures, basic explorations of both common and unusual antennas, antenna
modeling exercises, design improvements, antenna matching techniques from both a physical
and mathematical perspective, evaluations of mini-antennas and their underlying theory of
operation, new and patentable designs, propagation tutorials, and.... The list goes on,
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At the same time, antenneX has experienced continuous growth in its
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better. How? By submitting an article every now and then based on your current antenna
work that may be useful at any level to other readers.
Among the engineering and researching readers, there are
undoubtedly a number of unclassified and non-proprietary findings that antenneX
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If you are uncertain about whether your ideas merit an article, please feel free to send
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To see details of our writing guidelines, please look at: Writing for antenneX
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IN THIS ISSUE
We again include many fine articles by our great writing team from around the globe. Now, allow me to introduce this month's line-up of content:
OUR MONTHLY COLUMNS (plus this one you are reading by yours truly):
FEATURE ARTICLES IN THE LIBRARY:
Long-Wire
Antennas |
 In Parts 1 and 2, we examined the simplest unterminated and terminated
long-wire arrays using a single end-fed wire in both cases. Unterminated wires yield
essentially bi-directional patterns in line with the wire--more in line as the wire grows
longer as measured in wavelengths. There is a small residual front-to-back ratio
associated with long-wire end-fed wires, with the stronger lobes toward the open or un-fed
end of the wire. Adding a terminating resistor converts the bi-directional wire into a
directional beam, although the gain is about 4 dB lower than the strongest lobes of the
unterminated wire of the same length. At the end of Part 2, we summarized the shortcomings
of the single-wire terminated end-fed wire beam: "The lobes are split. There are many
side lobes. The forward gain is low." To overcome some of these problems, early
antenna experimenters invented the unterminated V array and the terminated V beam. We
shall look at each of these antennas in order, since we have some questions that parallel
those connected with the single wire terminated and unterminated antennas. For example,
will the terminated V beam show the same gain deficit relative to the unterminated V array
as the terminated single-wire did relative to its unterminated version? The V antennas are
so intimately related to the single long-wire antennas that before we move onward to
rhombics, we shall do a more detailed comparison. |
An 11-Element 2-Meter Yagi-Uda Beam for Backpacking by Robert K. Zimmerman, VE3/NP4B |
 Many
amateurs have the incorrect belief that offset feeding will result in some sort of
"unbalance" on the driven element. This is simply not the case, provided that
the driven element is assembled correctly. Actual tests, as well as NEC modeling verify
this fact. The radiated beam from an offset fed Yagi will still be on boresite.Here we discuss direct connection of the coax to a point on the driven element which is somewhat offset from the center in order to achieve a match. The technique is simple in concept and does not compromise the radiation bandwidth of the antenna. Offset feeding is particularly attractive for VHF/UHF suspension beams; such as the rollup backpacking Yagi discussed in last month's article, which could not easily support a gamma match structure. |
A
Backyard Random Wire Antenna - Part II |
 Part II of this article addresses measurements using available test
equipment to compare with the modeling results included in Part I. The antenna is still
the tree-to-tree installation using the same feed point location.Because of the non-available radiation field pattern measurement capability (near and far fields at different azimuth and elevation points), no comparison between actual and predicted patterns can be made. However, since the impedance shows some wide variation in the measured results, it no doubt can be accepted that external metallic object effects are definitely present. There are surrounding power lines, my aluminum tower and beam, and the 2-meter vertical mounted on the chimney, along with an old TV antenna and mast. As well, many surrounding homes use aluminum siding. I often read that others think modeling is overdone or perhaps too much emphasis is placed on the results. Quite clearly, the modeler is the controlling element in the exercise and the results must be read correctly. External antenna metallic object effects are always a variable and perhaps, if the modeler desired, could be introduced. Most often, in my own case, I find the modeling results to be very close to actual experienced results without additional inclusion of other disturbing element factors. |
Measurement
of RF Power |
 The measurement of transmitter output power is not a topic one expects to
find included in a discussion of antenna testing and design. However, discovering the
amount of power absorbed by the antenna, and losses along the way in the feedline, tells
us important things about the performance of the matching network, the feedline, and the
antenna, itself — the "antenna system."An overall theme is that we can learn a great deal about our antenna systems without investing a great deal of money. The purpose here is to show how we can measure RF power with simple equipment that can be built in the typical Ham's home workshop. When the radio amateur knows how much power a transmitter can deliver to a resistive load and how much power can be absorbed by an antenna, he understands the heart of his antenna system. When he also discovers the impedance of the antenna, and the nature and amplitude of the electromagnetic field it radiates, nothing about the performance of the antenna is left to chance. |
VENT
PIPE STEALTH, Version 2 |
 Vent Pipe Stealth, Version 2 (VPS2) is of a similar appearance to Vent Pipe
Stealth, Version 1 (VPS1) but has a low SWR at 433 to 455 MHz as well as 144 to 148 MHz.
This is achieved by sizing the diameter and length of the upper radiator to not mask the
third overtone response. I also changed the construction from VPS1 to use a more widely
obtainable and stronger insulator.Vent Pipe Stealth, Version 1 (VPS1) was a good broadband antenna that covered from the two-meter band up past 180 MHz while maintaining a low profile. This helps with the neighbors and family members concerned by the appearance of the roof, which they view as degraded by ANY structure they did not place there. Field test results of VSP1 were very encouraging. The gentleman (K5USS) who did these informal tests remarked that he could work repeaters that were not reachable with his other ground plane type antennas. I did some modeling that suggests that vertical dipoles have a distinct advantage over many other simple antennas for ground wave operation. |
A
New NCDXF/IARU Beacon Monitoring Program |
 In March 2006 Alex Shovkoplyas, VE3NEA, contacted me to be a beta tester of
his new automatic NCDXF – IARU beacon-monitoring program, Faros. To be honest I was
really surprised by the program possibilities at first startup. This was not just another
beacon monitoring program, but "THE Program" we were looking and waiting for.Faros is a fully automatic radio beacon monitor program, intended for Radio Amateurs, SWL listeners, and HF communication engineers, with many useful and practical features: Alex is a keen programmer and most of you will know about and use other most useful programs from the author such as: DXATLAS, IONOPROBE, HAMCAP, OMNIRIG, ROCKY, etc. Many readers appreciated in the past my Tutorial style of reviewing. Obviously, I maintain this preferred style. |
Well, there you have it, folks—thanks for listening and remember, the reading lamp is always on for you in the reading rooms. If I can be of further help, I'm just a Stone's Throw! away.-30-
Best reGARDS, Jack L. Stone, Publisher
jack@antennex.com
July 2006 antenneX Online Issue #111
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December 31, 2010
