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 |
|
Nulling an Unwanted Station:
Worse and Better Solutions
By L. B. Cebik, W4RNL
(A Posthumous
Publication) |
|
As
the number of VHF and UHF stations continues to multiply, seemingly
without limit, conflicts arise among services. Sometimes, they
involve two stations on the same or adjacent frequencies within the
same general service. At other times, there may be conflicts between
services in the same general area. When such conflicts arise,
solutions may emerge from general mediation or arbitration. In a few
cases, one service may have a clear legal or regulatory priority,
forcing a solution upon the other station in the lesser service. |
|
Radiation of Turnstile Antennas
Above a Conducting Ground Plane
By Kirk T. McDonald, PhD
Joseph Henry
Laboratories, Princeton University |
|
A "turnstile"
antenna consists of a pair of linear dipole antennas oriented at 90
degrees to each other and driven 90 degrees out of phase. The linear
antennas can be either dipoles or simply monopoles. Consider the
case that the length of the linear antennas is compared to a
wavelength so that it suffices to characterizes each antenna by its
electric dipole where the magnitudes p1 and p2 are
equal but their phases differ by 90 degrees, the directions of the
two moment differs by 90 degrees, i.e., P1*P2=0 and w
is the angular frequency. We discuss the angular distribution and
the polarization of radiation by turnstile antennas in various
configurations. The two antennas may or may not be at the same point
in space and they may or may not be above a conducting ground plane. |
|
Yagi Antenna Design Sensitivity
By
Dragoslav
Dobričić, YU1AW |
In my previous
simulations of wet antennas, I opted for “water foam” thickness on
antenna elements in order to improve accuracy of simulation and to
ensure fair enough comparison between antennas.
Some difficulties in the right choice arose because of the different
of antenna element diameters. The quantity of accumulated water on
elements might depend on its diameter. Water on elements produce
performance influence that is dependent on R/r, where r is bare wire
radius and R overall water covered wire radius. Ratio of these two
radiuses R/r is important for the wet antenna performance. This
water coating produces the effects of shortening in the element
wires, thus lowering the velocity factor which can be expressed as
equivalent distributed inductance L. |
|
Antenna Systems
By
L.B. Cebik, W4RNL (SK) |
|
Nothing in amateur radio provokes more debates than
antennas. And no aspect of the art of radio communications is so
filled with half information and downright misinformation. On the
other hand, when you leave behind the textbooks and try to construct
an antenna from available materials in the real world, nothing works
like the textbooks say it should. |
|
Magnetic Field of a Current Ring
By Douglas B. Miron, KC0NKY |
|
This article presents a closed-form expression for the magnetic
field at any point in space of a single-turn coil. Since the
expression uses elliptic functions, a very accurate
polynomial-and-logarithm approximation for the elliptic functions is
also given. The utility of this result is that the magnetic fields
and inductance of closely-wound coils can be calculated more rapidly
due to the elimination of one numerical integration in the process. |
|
Build an Air Variable Capacitor
By Thomas J. Nelson |
|
Variable capacitors are useful in a lot of situations. But,
adjustable plate capacitors bigger than 1000 pF are difficult to
find, and those that are available, tend to be inconveniently large.
There are several good tutorials on the Internet for building
rotatable air variable capacitors like those found in old AM radios.
However, because it's difficult to cut sheet metal into a curved
shape while keeping it perfectly flat, the plates have to be kept
far apart, which gives them a very low capacitance. The round shape
also tends to be bulky. I woke up one day and decided to invent a
new design that would be (1) compact and (2) have a high capacitance
(preferably above 5 nF). It should be easy to construct using
readily available parts. Should be easy, or so I thought. |
|
|
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 © 1988-2008 All rights reserved - antenneX©
Last modified:
June 02, 2008
|
