QEX №2 2014.pdf

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The national association for
225 Main Street
Newington, CT USA 06111-1494
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March/April 2014
About the Cover
QEX (ISSN: 0886-8093) is published bimonthly
in January, March, May, July, September, and
November by the American Radio Relay League,
225 Main Street, Newington, CT 06111-1494.
Periodicals postage paid at Hartford, CT and at
additional mailing offices.
POSTMASTER: Send address changes to:
QEX, 225 Main St, Newington, CT 06111-1494
Issue No 283
Harold Kramer, WJ1B
Larry Wolfgang, WR1B
Lori Weinberg, KB1EIB
Assistant Editor
Zack Lau, W1VT
Ray Mack, W5IFS
Contributing Editors
Production Department
Steve Ford, WB8IMY
Publications Manager
Michelle Bloom, WB1ENT
Production Supervisor
Sue Fagan, KB1OKW
Graphic Design Supervisor
David Pingree, N1NAS
Senior Technical Illustrator
Brian Washing
Technical Illustrator
Advertising Information Contact:
Janet L. Rocco, W1JLR
Business Services
860-594-0203 – Direct
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Circulation Department
Cathy Stepina,
QEX Circulation
225 Main St, Newington, CT 06111-1494 USA
Telephone: 860-594-0200
Fax: 860-594-0259 (24 hour direct line)
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Members are asked to include their membership
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Copyright © 2014 by the American
Radio Relay League Inc. For permission
to quote or reprint material from
or any ARRL publication, send a written
request including the issue date (or
book title), article, page numbers and a
description of where you intend to use
the reprinted material. Send the request
to the office of the Publications Manager
Michael Dzado, ACØHB writes about his “Eight
Channel Remote Control Antenna Selector.” With a
single coaxial cable run to his shack, he is able to
select between up to eight antennas. The Collins
Amateur Radio Club uses a pair of the selectors to
pick between several antennas and four radios. With
better than 70 dB of port-to-port isolation he is sure
the transmitted signal is going to the desired antenna!
In This Issue
A Different Type of Software Defined Radio — SDR
Based on
Michael Knitter, DG5MK
An Eight Channel Remote Control Antenna Selector
Michael Dzado, ACØHB
Actual Measured Performance of Short,
Loaded Antennas — Part 2
Barry A. Boothe, W9UCW
Radiation Resistance, Feed Point
Impedance and Mythology
Robert J. Zavrel, Jr., W7SX
78 GHz LNA Wrap-Up
Tom Williams, WA1MBA
Reprinted from
Proceedings of Microwave Update 2013
Upcoming Conferences
Index of Advertisers
ARRL: ........................................... 48, Cover III
Array Solutions: ........................................... 44
Down East Microwave Inc:............................. 7
Kenwood Communications: ................. Cover II
Nemal Electronics International, Inc: .............. 7
Quicksilver Radio Products................ Cover IV
RF Parts:................................................ 29, 31
Tucson Amateur Packet Radio: ................... 17
QEX – March/April 2014
The American Radio
Relay League
The American Radio Relay League,
Inc, is a noncommercial association
of radio amateurs, organized for the
promotion of interest in Amateur Radio
communication and experimentation,
for the establishment of networks to
provide communications in the event of
disasters or other emergencies, for the advancement
of the radio art and of the public welfare, for the
representation of the radio amateur in legislative
matters, and for the maintenance of fraternalism and
a high standard of conduct.
ARRL is an incorporated association without
capital stock chartered under the laws of the state
of Connecticut, and is an exempt organization
under Section 501(c)(3) of the Internal Revenue
Code of 1986. Its affairs are governed by a Board
of Directors, whose voting members are elected
every three years by the general membership. The
officers are elected or appointed by the Directors.
The League is noncommercial, and no one who
could gain financially from the shaping of its
affairs is eligible for membership on its Board.
“Of, by, and for the radio amateur,” ARRL
numbers within its ranks the vast majority of active
amateurs in the nation and has a proud history of
achievement as the standard-bearer in amateur
bona fide
interest in Amateur Radio is the only
essential qualification of membership; an Amateur
Radio license is not a prerequisite, although full
voting membership is granted only to licensed
amateurs in the US.
Membership inquiries and general corres-
pondence should be addressed to the
administrative headquarters:
225 Main Street
Newington, CT 06111 USA
Telephone: 860-594-0200
FAX: 860-594-0259 (24-hour direct line)
570 Brush Mountain Rd, Blacksburg, VA 24060
Chief Executive Officer:
The purpose of
is to:
1) provide a medium for the exchange of ideas and
information among Amateur Radio experimenters,
2) document advanced technical work in the Amateur
Radio field, and
3) support efforts to advance the state of the
Amateur Radio art.
All correspondence concerning
should be
addressed to the American Radio Relay League,
225 Main Street, Newington, CT 06111 USA.
Envelopes containing manuscripts and letters for
publication in
should be marked Editor,
Both theoretical and practical technical articles are
welcomed. Manuscripts should be submitted in word-
processor format, if possible. We can redraw any
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Any opinions expressed in
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the authors, not necessarily those of the Editor or the
League. While we strive to ensure all material
is technically correct, authors are expected to
defend their own assertions. Products mentioned
are included for your information only; no
endorsement is implied. Readers are cautioned to
verify the availability of products before sending
money to vendors.
Larry Wolfgang, WR1B
Empirical Outlook
ARRL Centennial Celebrations
By now I am sure all of our readers are aware of the many ARRL Centennial events taking place
throughout 2014. The excitement level around ARRL Headquarters is very high, and it is easy to
sense the growing anticipation of many events coming up later this year. The National Convention
in Hartford, Connecticut on July 18 through 20, 2014 is causing quite a stir, since many
Headquarters Staff members are playing a major role in planning this event. Oh, we participate in
National Conventions every year, and there are always several other major conventions that
require a bit of extra planning and participation by Staff members. We don’t normally have much
to do with the overall convention planning, though. That is usually handled by the committee mem-
bers from the area local to the convention who plan that gathering every year.
There hasn’t been a major ARRL Convention in the Hartford area in recent memory. Luckily, we
have lots of help from many of the people who organize the New England Division Convention in
Boxboro, Massachusetts every other year, as well as a dedicated group who have been putting on
the popular “Nutmeg Hamfest/Connecticut State Convention” for a number of years. Even so, the
buzz around here from all the additional activity of planning the Centennial Convention is palpable.
Of course State and Section Conventions across the country will be a bit extra special this year.
I am sure there is a lot of similar activity to go along with planning all those events. I hope you plan
to participate in or at least attend your local hamfests and conventions, as well as travel to one or
two of the larger events.
There are a number of special operating activities that you can participate in from the comforts
of your own radio shack, as well. I previously mentioned the ARRL Centennial QSO Party as one
of those activities. This is shaping up to be a fun on-the-air event, even for the most casual opera-
tors. Just spend a bit of time on the air, make a few QSOs, and submit your logs to Log Book of
the World. As your logs are processed they are cross checked, and points are awarded based on
the confirmed contacts with other ARRL members. You don’t even have to keep track of the points
values, although I think it is fun to find out what appointments and positions my contacts have in
the ARRL Organization. In the Nov/Dec 2013 Empirical Outlook I mentioned that I had been told
QSOs with your
Editor were worth 30 points. In a later refinement of the “Rules” all ARRL
Headquarters Staff Members became worth 50 points per contact. So, it’s even better than I first
Have you been chasing the portable W1AW operations? I have managed to contact most of
them so far, but I’ve already missed a couple so I am looking forward to the second operation from
at least some of the states. It seems to me that the operators tasked with these “Field Operations”
have been doing a great job, using the popular modes and having one or more operators on the
air at all times. At least I have found it pretty easy to look them up on the DX Cluster and then with
some patience to get them in my log. You can check the schedule for which states and territories
will be on with the W1AW portable call sign on the ARRL website:
www.arrl.org/files/file/On the
There are two portable operations, each lasting one week, with each
state being on two different weeks during the year. As an added bonus, The Hiram Percy Maxim
Memorial Station at ARRL Headquarters is operating as W100AW. Find a guest operator or
maybe even an ARRL Staff Member operating from one of the studios, and have fun chatting with
this special event call sign.
My Christmas Wish List for last year included a Raspberry Pi. Jean, WB3IOS, saw fit to fulfill
that wish, so I was thrilled to find a Pi under the tree on Christmas morning. I am still very much
at the bottom of the learning curve with this little circuit board, but it is definitely fun to play with. Of
course, I’ve had to add a few “accessories,” so I can start to learn about inputs and outputs, to
explore some things I can do with the computer. The “Operating Manual” I found on line was two
pages of quick-start instructions, so I have also had to go looking for a bit more documentation. I
have never used a computer running any version of
and it’s been quite a few years since I
have done much with running a computer from command line entries, so I have some challenges,
but I think that adds to the fun. I am sure many of you are reading this and laughing at my lack of
knowledge and experience.
I have found several websites describing some fun Amateur Radio applications, and there are
several ideas I want to explore. I have managed to install XASTIR (X Amateur Station Tracking
and Information Reporting) and get it running. No great accomplishment, since many have already
done this. My challenge was figuring out how to put some downloaded maps into the program’s
Maps directory. That was one of those
challenges. All of the descriptions I could find
assumed that I would already know how to copy files into the root directory.
Eventually I want to acquire a small monitor that runs on 12 V and have a computer system that
I can use in the car or while on camping trips. With a modem and radio I’ll have an APRS station
ready to go anywhere. Oh, the possibilities seem endless as I begin to learn more about this little
If you are reading this and thinking about how much more advanced you are with using your
Raspberry Pi, I would like to encourage you to write about some project or application that you
have found. I’ll bet there are many other readers who would benefit from your expertise. I’ll be
looking forward to hearing from you!
QEX – March/April 2014
Michael Knitter, DG5MK
Weissenburger Weg 5, 45701 Herten, Germany;
A Different Type of Software
Defined Radio — SDR
Based on
Software Defined Radio is a good example of hardware and software integration in
Ham Radio.
as a graphical programming environment, keeps away from
a lot of program syntax. It frees up the programmer to focus on the system from a
holistic point of view. This article shows the development of a SDR based
and common hardware frontends.
Some years ago, I started with SDR
and was excited about the capabilities and
opportunities. With minimal investment, I
was able to work all types of modulation
while having a very comfortable PC user
interface. Frequency spectrums and their
usage, image frequencies and modulation
suddenly became visible.
One day my son called me to help program
his LEGO NXT robot. Programming was
done with a graphical program called
where everything operates by drag and drop.
showed up to be a dramatically
reduced version of National Instruments
I was surprised and amazed and an
idea started to form up in my brain to create
a real time SDR with such a system.
By taking self study lectures on
some major advantages showed up compared
to a classical text oriented programming
environment like C. Many functions, from
graphics to DSP, are available by drag and
drop. I was more and more able to focus
on the overall system and its functionality
because the programming details are moved
to the background. The block diagram you
create is the program itself; the concept of
a block diagram should be very familiar to
many amateur radio operators.
Front Panel
Figure 1 shows the front panel of the
Figure 1 — Screen capture showing the SDR front panel
finalized SDR receiver with signals in
the 40 m band. Major features are two
independent receivers, a Softrock compatible
SI570 frequency control, demodulation of
SSB and AM signals and the implementation
of different kinds of filters. The program is
able to use internal and external soundcards
from common SDR hardware front ends.
Operating Mode
Figure 2 shows the
block diagram
of the RX program version 1.2.1. A larger
version can be found on my web page
because it is too large to print clearly as part of
this article.
It seems to be overwhelming, but
notice that this is the whole program. It has to
be compared to thousands of lines of code in
a standard text oriented program like
can easily identify the different functional
blocks in the enlarged version. Figure 3 shows
the building blocks of the SDR program.
Notes appear on page 7.
QEX – March/April 2014
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