was a regular and popular monthly column by L. B. Cebik, W4RNL (SK) Because
computerized antenna modeling has become widespread, and its popularity as a design tool
continues to increase, this series is devoted to helping readers get the most from the
design software used. The articles focus upon the use of NEC and MININEC, along with
useful adjunct software as well.
This column is primarily for "Guest
Editorials" to provide a podium for our readers to voice their opinions to the rest
of the world too. This is a chance for readers to get on their "soapbox" and
speak about antenna and radio-related subjects. Don't miss these interesting views about
anything and everything about radio and antenna systems! Now, what have YOU to say??
Ham WorkShop, is also another
regular monthly column filled with a variety of "RADIO-STUFF" of value to
almost everyone in amateur radio from Novice to Extra and those just beginning to take up
this special hobby. This includes subjects, but not limited to: VHF, choosing the right
antenna, coax cable, small to mid-scale construction projects in a practical manner, use of test
equipment, etc. It is also meant to help readers become more familiar with the technical
jargon and the fun side of radio.
Stone's Throw! a
monthly column by antenneX publisher,
Jack L. Stone, among other things, is to keep
the readers informed about our progress, new developments, plans for the future, and to
introduce the authors and their subjects each month. Also, our main slogan around here is
"we aim to please", so this serves as a place for the readers to tell the
publisher what is wanted or at least make suggestions. Just remember, the publisher is
only a Stone's Throw away! Go in for a visit and read this month's column.
another monthly column by Marcel H. De Canck, ON5AU of Belgium. Signal propagation
is a subject that is one of the most basic ingredients of radio and is something everyone
in radio should know about in order to maximize communications in the most effective way.
Its not enough to have the best equipment and the best antenna if you are trying to
send out a signal against a brick wall. Conversely, one may possess a very crude rig,
running low power, but yet transmit/receive a signal to great distances with ease, simply
by making use of a thorough knowledge about how signal propagation works within the
environment. Follow this column and learn more about propagation!
author of the monthly column Antenna Design & Use
is Justin Johnson, G0KSC who does in fact design and install antennas in
many parts of the world. He's a real hands-on expert with years of
experience in this field. Following this column will be helpful
especially to those pondering a new antenna project. Examples of how to
model the designs will appear at times as well. There is something here
for just about everyone wishing to know more about how antennas are
created, tested and used.
The Radio Corner is a monthly column by Robert Gulley, AK3Q, devoted to exploring radios and radio-related topics
of all stripes. The radio is the other essential half of the antenna connection, and the possibilities for
both are almost endless. From antique radios to high-tech Software-Defined Radios, and everything in
between, each edition of The Radio Corner explores radios, software, hardware and almost anything
radio-related. Amateur, shortwave, digital, utility, broadcast, military and civilian aeronautical radio
are just some of the topics covered by Robert, and no doubt readers will want to build even more antennas
after exploring these facets of the radio hobby!
FEATURE ARTICLES THIS MONTH IN THE LIBRARY Subscription Required to View Click to
Babinet's Principle for Electromagnetic Fields
In optics, Babinet's principle for complementary screens is that the sum of the wave
transmitted through a screen (usually considered to be "black" except for its apertures),
plus the wave transmitted through the complementary screen, is the same as if no screen
were present. An electromagnetic version of this principle was given by Booker, who
considered perfectly electrically conducting screens and argued that the electromagnetic
fields in the case of the complementary screen (labeled with a ′) that appear in Babinet's
principle should be the dual fields -B′
and E′ rather than the nominal fields E′ and B′.
Practical Antennas: Part 8.07
The driver elements position in an interlaced multiband Yagi,
either using coupled resonator system or direct-drive feedline, plays a certain role. When moving a driver
element position, also the other elements related to that Yagi driver element have to move. Thus, the spacing
between all the multiband elements are shifted and changed. Also the mutual couplings between any elements
become different. Any changes influence the antenna performance, either minor or significant.
To investigate the impact of these element position moves, I will make a study with an overall design.
This dual-band design begins with a 3-element wideband 15-meter Yagi capable of matching a 50-Ohm main feedline.
Direction-Finding: The Sport of Hams!
I must confess to
getting rather excited. I know it is early days yet, but before long next September will be here and the seventeenth USA
and Ninth IARU Region 2 ARDF Championships will be underway right here in my home town. Our club is going to be the main
host for this event, as we have two nationally known champions as a part of our group. I am particularly looking forward
to seeing (and hopefully discussing) antennas with some of the participants - what they use and why.
Direction-finding is a very special niche of amateur radio, not only because of the international sport it has become,
but also because the techniques used often emphasize opposite aspects of our normal antenna design. This is instructive
not only for locating the "fox" (or interference or an offending transmission), but also for our testing and design of everyday antennas.
Links and Tips from Around the Web
There are so many great
resources around the web (like antenneX!) one can spend more time exploring than actually
operating. I try to find a good balance in that my first love is amateur radio, but I am not
so set in my ways I cannot find great value in the multitude of resources available to us today.
I have some cronies who will simply not get on the Internet, or even use a computer.
"Paper logs are good enough!" they say.
This time around I thought I would share some of the more useful resources I have found, with the hope at least
some of them will increase your enjoyment of this great hobby.
Notes on Fat-Wire Dipole Convergence:
MININEC, NEC-2, NEC-4
A standard dipole at HF made from commonly used materials can
be accurately modeled in any of the NEC-based programs using minimally
recommended segmentation. Convergence testing (increasing the segmentation
density) confirms the accuracy of the model for virtually any purpose the
model might be used.
Similar behavior is often expected from dipoles of increasing diameter, for example up to 1'
at 14 MHz. 2 * PI * radius (circumference) / wavelength must be much less than 1, a condition
easily met by this large dipole. MININEC prefers the largest minimum segment length to diameter ratio: 1.25:1.
This condition is easily met if the segmentation density is about 40 per half-wavelength or less.
Even within program limitations, however, the modeler encounters some interesting program-to-program
variations that are worth noting. They may not be operationally significant in terms of model
reliability. Still, they will increase our awareness of program tendencies and trends, thus
enabling the modeler to view a certain set of progressions as either expected or unusual.
Multielement Arrays: A Mutual Attraction Part
Multielement arrays are an elegant solution to adding directivity to our signals. There are many,
many different designs, and there are even the ones yet to be developed. As noted in Part 1 of this
series Multielement Arrays work on the electrical principle of coupling, typical referred to as driven
arrays or parasitic arrays. They may also be broadside arrays, end-firing arrays, and bi-directional
arrays. With this much variety there is real room for creativity, while still being able to utilize
the laws of physics. Let's look at a little more theory and then look at some of these antennas to
see just how they are designed.
?need a compact
signal problems either transmitting or receiving ? can't choose between a vertical or horizontal antenna
to learn about antenna modeling
want to know more about propagation
? want to design an antenna, but don't
want to redo the wheel
a program for antenna design and antenna plotting
know what antenna is best for hamsats or others
a busy mobile signal on all bands
an inexpensive directional antenna for 10 meters
a low-noise antenna for 160 meters
to know if someone else has solved your problem
a disguised mobile antenna for the vehicle
want to know more about antennas