Read
Our Monthly Columns! |
| Antenna Modeling |
From The Shack |
 This
is a regular and popular monthly column by L.B. Cebik, W4RNL 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 |
Stone's
Throw! |
|
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' 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. |
Propagation |
 Propagation
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.
It’s 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! |
FEATURE ARTICLES THIS MONTH IN THE LIBRARY
Subscription Required to View
Click to
Subscribe |
|
Designing Multi-Band Parasitic Beams
Part 6: Small Yagi-Yagi Alternatives to the Moxon-Yagi 2-Band Beam
By L. B. Cebik, W4RNL (SK) |
|
The summer VHF DX season held up well through July 2008, and six meters
was fairly active even into mid-August, but faded fast after that.
I’ll be turning my attention back to the lower frequencies, but have
one more installment in this series of articles on VHF gain
antennas. In Part 2 of this series we examined a design that
emphasized gain somewhat at the expense of other antenna
characteristics, especially side and rear rejection. This time we
look at one that obtains an excellent overall pattern by balancing
forward gain and front-to-rear performance with good SWR bandwidth.
Along the way to building this antenna I restored and reused some
old parts from my previously disclosed “boulevard of broken beams.” |
|
Practical Antennas: Part 2.1
By
Marcel H. De Canck, ON5AU |
|
The ionosphere plays a tricky but an important
role to our radio communications, and there is very little we can do
about it. But there is plenty you can do about having a good and
efficient antenna system. Yes, antenna system, it’s not the antenna
itself but the whole part as transmission line, and matching
properly the transceiver and the antenna to the transmission line.
It is a breath-taking concept that a simple length of wire or rod or
tube can transform electrical energy into invisible radio
electro-magnetic waves that can cross the space at the speed of
light.
How does an antenna system works? Why does the antenna radiate
electro-magnetic waves? These questions I heard many times and the
answers are not given with few words. Never-the-less, many books and
some of great weight and complexity have been written about antennas
and many antenna types have been developed and build. Often it is
not comprehensive to the layman to fully understand the whys and
hows of the radiation capabilities of an antenna and these counts
even for the simplest ones like a dipole or a groundplane. Also I
often hear many times misconceptions about antenna properties and
characteristics. To start with, understanding why and how a simple
antenna effective radiates will be explained in a clear view. The
dipole is the best antenna to do that and once the secrets of the
dipole characteristics and properties are fully understood it will
be much easier to have a clear insight of the hows and whys of more
complicated antennas.
The first episodes will handle completely about antenna fundamentals
mostly with the half wavelength dipole as study example. The dipole
is also often a part element of more complicated antennas such as a
Yagi and others. In particular for the low frequency bands, the
dipole is used by many radio amateurs as transmitting or receiving
antenna and its many practical installations and shapes will be
fully studied and explained in a chapter later on. In fact many
other antenna types will become subject to explanation as the
antenna story develops. |
|
NewcomerNotes: Short Wave Listening
(SWL)
By Robert Gulley, AK3Q |
One of the things which makes the
radio hobby so pleasurable for me is how easy it is to find
interesting things to listen to on whatever radio happens to be
handy. From the cheapest AM-only radio to the fanciest software
defined radio and beyond, every listening opportunity holds the
potential for something enjoyable with even the smallest effort.
When was the last time you listened to AM radio late at night to
hear stations from far away? A local group to which I belong
sponsors an informal “ULR” DX Award for folks who snag 10 or 20
states using their ultra-light radios such as the Sony SRF-59 or
similar. No one is going to argue ultra-light radios out-perform
larger, more robust radios—that’s not the point. What makes
attaining the award fun is seeing what can be accomplished with such
meager means, and the operant word here is fun! With a radio so
light I can forget it is hanging around my neck, stations from
hundreds of miles away come in like they were next door. Sure, I can
hear more stations and far more distant stations on my Icom or my GE
Super Radio II, but listening to the ultra-light definitely has its
place. Going in the opposite direction can be just as fun. Find the
biggest, oldest, clunkyist radio you can and see what comes over the
speaker—chances are you’ll be pleasantly surprised! |
|
Visualizing Antenna Fields
By Ron Nott, K5YNR |
|
The method of
visualizing antenna fields as presented here must be categorized as
theoretical because as of yet, instruments are not available to
provide direct observations. It has been said that the reason
mankind has made so much progress in science over the last century
is due to learning to make accurate instruments, rather than
improved imagination techniques. But the following will require that
you exercise your imagination because the instrument to do the
observation has not yet been invented. Perhaps your imagination will
be challenged into thinking about such an instrument by what follows
in this controversial article. |
|
The 6-10 Z-pole
Antenna
By Edward J. Shortridge, W4JOQ |
|
Both
the 6- and 10-meter bands can be exciting with DX signals that pop
up with surprising signal strength. These wonderful DX conditions
might not have existed for a long time, but if you want to take
advantage when conditions are right, you might consider the
following antenna.
A Duel-Band antenna is being presented that covers the 6- and
10-meter bands. Vertical and horizontal versions are considered.
Both versions are intended to use moderate size step-diameter
aluminum radiators at 10 meters. The vertical version has a radiator
that extends from 22 to 39 feet above Average Soil while the
horizontal version is mounted at a 30-foot height.
The 6- and 10-meter bands are quite wide and if you might consider a
J-pole vertical antenna, you will find it has a very limited SWR
bandwidth totally inadequate for use across the entire bandwidths.
Additionally, making a J-pole into a duel band antenna might be
impossible. |
|
Coaxial Cable Feeder Influence on Four
Stacked Yagi Antenna Array
By Dragoslav Dobričić, YU1AW (Serbia) |
A previous article series consisted of
two parts showing the results of investigating how a coaxial cable
antenna feeder influences antenna performance in a situation when
minimum and full interaction between antenna and cable is achieved.
Investigations were conducted by computer simulations of six
different antennas under the same conditions.
In the first part of the previous series, results show a high degree
of dependence on cable approaching angle alpha to antenna driven
element. This happened despite that the approaching angle alpha was
always kept lying in the antenna symmetry plane in order to maintain
minimum interaction between cable and antenna. Even under these
idealized conditions and in the absence of any other environmental
effects, results show considerable antenna performance degradation
for some antennas.
In situations when we use a horizontally stacked antenna array, it
is simply not possible to have the cable lying in the vertical plane
of antenna symmetry. In the second part of the article series, we
presented results of investigations conducted on how coaxial cable
influences antenna performance when it is not lying in antenna
symmetry plane. It is usually used for feeding two horizontally
stacked antennas or four antennas stacked two over two, or due to
any other reason depending on mechanical support construction
demands. In this situation, the cable cannot lie in the antenna
symmetry plane, and it is approaching a Yagi antenna’s driver
element under some angle beta which is lying in the plane
perpendicular to the antenna symmetry plane. In such case,
cancelations of some effects were present in a lesser degree and we
got more influence than in a situation when the cable was lying
exactly in the antenna symmetry plane. In this situation it was also
noticeable that coaxial cable became a significant part of the
antenna’s radiating structure. Due to significant coaxial cable
influence and radiation, antenna radiation diagrams in both planes
were considerably distorted.
In this article we will present results of an investigation on how
coaxial cable feeder influences four Yagi antennas stacked in an
array two over two when cables are arranged in a few different ways.
|
|
|
ARCHIVES Volume I, II, III, IV, V, VI,
VII, VIII, IX & X available!
Go
Here to See List of Articles
|
? need a compact
antenna
? have
signal problems either transmitting or receiving
? can't choose between a vertical or horizontal antenna
? want
to learn about antenna modeling
? just
want to know more about propagation
? want to design an antenna, but don't
want to redo the wheel
? need
a program for antenna design and antenna plotting
? don't
know what antenna is best for hamsats or others
? have
a busy mobile signal on all bands
? need
an inexpensive directional antenna for 10 meters
? need
a low-noise antenna for 160 meters
? want
to know if someone else has solved your problem
? need
a disguised mobile antenna for the vehicle
? just
want to know more about antennas |
Then you need
to subscribe to antenneX ONLINE!
...
Send mail to webmaster@antennex.com
with questions or comments.
Copyright © 1988-2009 All rights reserved - antenneX©
Last modified:
December 31, 2008
|
