Folks: The new antenneX
online issue #197 for the month of September 2013 is ready to read at your pleasure!
IN THIS ISSUE
We again include many fine articles by our global writing team. Now, please allow
me to introduce this month's line-up of content:
OUR MONTHLY COLUMNS:
Modeling By L. B. Cebik, W4RNL
This column has ended with 147 articles.
From the Shack
Russ T. Nobs
Old Timer's Musings- Giving Back
Amateur radio’s uniqueness as a
hobby comes out in many ways, not the least of which is the spirit of
giving back to the hobby through mentoring new amateurs. Ours is a hobby
which is more caught than taught—which is why sharing what we do, why we
do it, and how we do it really requires the "personal touch" of an
Elmer. To use a well-worn, but perceptive phrase, we stand on the
shoulders of those who came before us. We are either building on the
ideas of others, or we are relaying (or learning) from the experiences
By various authors
An open column
subject to additional articles.
By Marcel H. DeCank
This column has
ended with 87 articles.
Antenna Design & Use
The Radio Corner
By Robert Gulley, AK3Q
There is an old saying which goes
something like this: “the only difference between men and boys is the
price of their toys.” No doubt there is a lot of truth to that adage,
but I think it also underscores an aspect of one’s hobbies or interests:
whatever one’s passion, it is just that—a passion. The radio hobby is a
passion for me, and it stirs within me not only memories of childhood,
but also some of the sense of adventure and wonder that is common as a
kid. The more you discover about radio the more you want to participate,
and that means lots of radios and radio accessories!
readily admit I have more radios than ought to be allowed, both old and
new. I also have a lot of radio accessories which make the hobby that
much more enjoyable, and so I thought I would share some information
about those accessories in the hope that some of them might add to your
pleasure as well.
- Stone's Throw!
By Jack L. Stone, Publisher
A monthly column covering breaking news, new concepts and products,
people making news and introduction of the current month's issue articles and its
authorsalthough not limited to this only.
This month, the topic is:
Flipping Over Solar Maximums
FEATURE ARTICLES IN THE LIBRARY
OF NEW ISSUES:
Matching and Myths of J-Poles - Part 4
I can't claim that I have solved all of the
possible issues but I will shed some light on some of the
functional concepts of J-Poles and some basic problems I have
not seen discussed, including some matching techniques that
certainly seem sub-optimal to me.
Most authors omit that we are referring to electrical lengths
instead of physical lengths, assuming that the reader knows this
already. I will state that this is sloppy writing. If you are
telling the reader something you assume he already knows instead
of approaching it from the point of view that you are
instructing someone who does not fully understand the subject,
why are you wasting the learner's time and the publisher's space
with only partial information? So, the learning process starts
with this 3-part series on J-Poles.
Practical Antennas: Part 6.12
Marcel H. De Canck, ON5AU
simple array that has been mostly forgotten by hams is the Bruce
array, in spite of it has been around since the late 20s. Edmond
Bruce took out a patent on this antenna in 1927. A few
variations of the Bruce array are illustrated. It is
simply a continuously wire one or more wavelengths long, folded
so that the currents in the vertical portions are in phase. To
ensure that the array is vertically polarized, (at least as a
starting principle), we shall feed it at the center of any
vertical element. The square loops in the Bruce behave very much
like quad loops. As can be noticed in a graphic, it carries the
vertical sections large in-phase currents, while the horizontal
sections carry the small currents flowing in opposite directions
with respect to the center of a section.
Directional Antennas in
Small & Noisy Places: Part 1
By Robert Gulley, AK3Q
There is no question that a good directional antenna has
numerous advantages over a non-directional antenna, as well as
some important disadvantages. My ideal antenna farm would have a
good selection of both, with plenty of room for them all. My
reality, like many others, is somewhat less appealing. I am on a
small lot and in a noisy location. Unfortunately this is
becoming more the rule rather than the exception, so the
question becomes how do we do more with such handicaps?
In answering this question for my own situation I have found
several workable ideas which I hope you will be able to use or
adapt to your own circumstances. In this Part 1 I examine
shortened Yagi antennas for their directional properties and for
their noise reduction capability. They can also be modified to
work in relatively small spaces with a minimum of compromise.
The goal here is to keep things as simple as possible (no traps
or capacitive hats), and to work within realistic limitations.
In Part 2, I will suggest some other antenna options, still with
the goal of working within a small space.
The "Magic" Rhombic
By Robert C. Wilson, AL7KK & VE7ZKK
Way back about two thousand years ago someone developed a “Magic
Square.” It looked like this:
4 9 2
3 5 7
8 1 6
Notice every way you add the
numbers, horizontally, vertically, or even diagonally, the sum
comes to 15 !!! It works properly no mater which way you add.
Well I have a "Magic" Rhombic for you. No matter which high
frequency band you want to work it will do the job from 80 to 10
meters. Not only will it radiate on each band but it will always
direct your signals in the same direction! Just like the Magic
Square this rhombic is also a SQUARE!
Ladder Line Antennas
By Heikki Antman OH7ND
The Yagi-Uda antenna is familiar as
the commonest kind of terrestrial TV antenna to be found on the
rooftops of houses. It is usually used at frequencies between
about 30MHz and 3GHz, or a wavelength range of 10 metres to 10
cm. (There are some obsessional amateur radio enthusiasts who
construct Yagi-Uda antennas for the 80 metre wavelength band.
This is rather impractical as spacing them from the ground by
more than half a wavelength is difficult.) The rod lengths in a
Yagi-Uda are about a half wavelength each, and the spacings of
the elements are about 1/3 of a wavelength. This puts the
overall sizes of Yagi-Udas within the ranges.
By L.B. Cebik, W4RNL (SK)
In some previous
notes I developed on traps left me with some unanswered
questions. For example, low Q traps appeared to unduly affect
antenna gain. Traps using certain forms of linear or
transmission-line stub inductors appeared to yield dipole gains
above standard full size models. The only way to settle some of
these questions is to do some systematic modeling and watch the
This brief report is the first step in
the process. It models a 10-20 meter dipole using traps that
consist of 1.2 microH inductors and 26.92 pF capacitors,
resonant at 28 MHz, consistent with common trap practice. As
previously noted, the traps are treated as loads on the ends of
the 10 meter sections of the antennas. Modeling the traps
consisted of calculating the requisite value of the equivalent
parallel resistance for each trap Q level for each of the two
bands and then inserting the trap as a parallel R-L-C load in
the last segment of the outer ends of the 10-meter wire, with
20-meter wire extensions added. The antennas used approximate 3"
segments throughout. Hence, trap length is considered for these
models to be 3" per trap.
The total antenna assembly was
resonated within +/-1 Ohm of reactance on each band for each
wire size and level of Q. Selected frequencies were 28.5 MHz and
14.175 MHz, which were considered fair samples of antenna
performance with the traps selected.
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Jack L. Stone, Publisher
antenneX Online Magazine
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