QEX №6 2014.pdf

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The national association for
ARRL
AMATEUR RADIO
225 Main Street
Newington, CT USA 06111-1494
TM
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November/December 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 287
Harold Kramer, WJ1B
Publisher
Larry Wolfgang, WR1B
Editor
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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860-594-4285 – Fax
Circulation Department
Cathy Stepina,
QEX Circulation
Offices
225 Main St, Newington, CT 06111-1494 USA
Telephone: 860-594-0200
Fax: 860-594-0259 (24 hour direct line)
e-mail:
qex@arrl.org
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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
QEX
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
(permission@arrl.org).
Colin Brackney, KR4HO, discovered an old Kenwood
TM-241A 2 m FM transceiver that a friend had left
with him. In addition to the 2 m band, this radio also
tunes 118 to 135.995 MHz to cover the AM aircraft
band. Colin decided to build a “A Receiving Converter
for 2 Meter Radios” and can now receive AM and FM
from 18 to 74 MHz. As a bonus, he added coverage
for 218 to 235 MHz.
In This Issue
Features
3
14
25
31
35
44
Controlled Envelope Single Sideband
David L. Hershberger, W9GR
A Receiving Converter for Two-Meter Radios
Colin M. Brackney, KR4HO
Experiments With Eddy Current Methods for
Thickness Measurement of Thin Metallic Materials
Dr George R. Steber, WB9LVI
New Life for the Motorola MSR-2000 VHF Repeater:
A New RF Power Amplifier
Tom Wheeler, NØGSG
The Development of the Low Phase
Noise Double Tank Oscillator
Colin Horrabin, G3SBI
Bob Zepp: A Low Band, Low Cost, High Performance
Antenna
Robert J. Zavrel, Jr, W7SX
Index of Advertisers
ARRL: ................................................Cover III
Down East Microwave Inc:.......................... 24
Kenwood Communications: ................Cover II
M
2
:............................................................... 13
Nemal Electronics International, Inc: ...........24
Quicksilver Radio Products............... Cover IV
RF Parts:............................................... 41, 43
Tucson Amateur Packet Radio: .................. 30
QEX – November/December 2014
1
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
affairs.
A
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:
ARRL
225 Main Street
Newington, CT 06111 USA
Telephone: 860-594-0200
FAX: 860-594-0259 (24-hour direct line)
Officers
President:
KAY C. CRAIGIE, N3KN
570 Brush Mountain Rd, Blacksburg, VA 24060
Chief Executive Officer:
DAVID SUMNER, K1ZZ
The purpose of
QEX
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
QEX
should be
addressed to the American Radio Relay League,
225 Main Street, Newington, CT 06111 USA.
Envelopes containing manuscripts and letters for
publication in
QEX
should be marked Editor,
QEX.
Both theoretical and practical technical articles are
welcomed. Manuscripts should be submitted in word-
processor format, if possible. We can redraw any
figures as long as their content is clear.
Photos should be glossy, color or black-and-white
prints of at least the size they are to appear in
QEX
or high-resolution digital images (300 dots per
inch or higher at the printed size). Further
information for authors can be found on the Web at
www.arrl.org/qex/
or by e-mail to
qex@arrl.org.
Any opinions expressed in
QEX
are those of
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
The Year in Review
As we wrap up the November/December 2014 issue of
QEX,
I can’t help but reflect a bit on
the year that has been. Well, in reality I am quite happy that there are still nearly 3 months to go
in 2014. I’m not ready for this year to be over just yet, but even from my early October perspec-
tive, it is rapidly coming to a close.
Of course everyone knows that 2014 has been the ARRL’s 100
th
Anniversary. It has been a
year-long celebration, with many memorable events. I hope many of our readers have enjoyed
at least some of them.
As a ham for about 45 years, and also as a person who is very interested in the technical
aspects of our hobby, sometimes my interest in on-the-air operating has waned a bit. I imagine
that is fairly typical of anyone who has been licensed that long. I’ve never completely lost my
interest in getting on the air, but sometimes it is easier to pick other pastimes. This year I have
been more active throughout the year than I can remember in recent times. Several things have
helped fuel that interest.
The ARRL Centennial QSO Party has been a lot of fun. I have enjoyed several multiple-hour
operating stints of just getting on the air and chatting with fellow hams. There were a couple of
“Red Badge Days” advertised, with an emphasis on getting on the air and contacting ARRL HQ
Staff members as well as elected officials. Those activity days could only be successful with the
ARRL Membership if the “Red Badge” folks were actually on the air making contacts. While I
didn’t spend any whole days operating, I did try to put in a couple of hours at a time, and I found
this to be a lot of fun!
Another activity that has really captured my attention throughout the year has been the
W1AW special event stations. I didn’t put as much effort into contacting some of the earliest
states, so I missed a few and am still waiting for the second go around for a couple of those. I
won’t miss them the second time. At this point I have contacted all but three of the states on both
CW and SSB. I am feeling pretty confident about meeting my goal of a W1AW Worked All States
certificate on both modes.
One unintended consequence of all this activity has been the realization that I was fairly close
to earning several other awards. I have a mixed mode Worked All States Award going back to
sometime in the early 1980s, and I also completed my mixed mode DXCC in 1995. I haven’t
actively pursued new band/mode states or countries towards endorsements since then. While
looking at my Logbook of The World records late this Spring, I realized that I was not all that far
from completing WAS and DXCC on both Phone and CW. Since then I’ve done a little targeted
DX operating, and now have over 100 Phone QSL records in my LoTW account, and currently
stand at 92 on CW. I’ve worked at least 8 more countries on CW, but the QSL records have not
come through yet. With help from the ARRL Centennial QSO Party and the W1AW Special
Event Stations, I have WAS confirmed on CW and Phone now.
As I looked at some other awards listings, I realized that I could also update my mixed mode
Worked All Continents Award with both CW and Phone Awards. My plan is to apply for all of
these awards/endorsements as soon as I have those last 8 DXCC CW QSL records in LoTW.
This is really fun!
I have previously mentioned the ARRL National Convention in Hartford on this page. What a
spectacular event that was! I have not been to a National Convention in quite a few years. This
one would have been worth the trip from almost anywhere. I’m glad it was practically in my
backyard!
Over the last 12 months I have been reading and learning more about software defined radio,
and digging a little deeper into some of the math behind what goes on inside our modern radios.
I have also found myself learning a little bit about
Linux,
or at least the
Raspbian
version used
with Raspberry Pi computers. I’m still trying to gain a better understanding of why an operating
system designed for use with this little computer always seems to require additions/deletions/
other changes to make it work with various applications, but at least I have become a little fa-
miliar with the terminology. The Raspberry Pi is a fun little box to play with.
I have also recently mentioned that I have flashed the Broadband-Hamnet firmware into a
pair of Linksys WRT54G wireless routers, to create my own little Mesh network. I still have a lot
to learn about using this Mesh network, but it’s a start. It looks like I’ll have plenty of projects to
keep myself busy for some time to come!
What gets you excited about Amateur Radio? I hope you have been enjoying and learning
from the great articles that we have had in
QEX
over the past years. I can assure you that there
are more good articles to come in 2015, but I also need you to write about the projects and top-
ics that interest you. A lot of others want to learn from your experience and expertise! Have fun.
2
QEX – November/December 2014
David L. Hershberger, W9GR
10373 Pine Flat Way, Nevada City, CA 95959;
w9gr@arrl.net
Controlled Envelope
Single Sideband
Introducing Controlled Envelope SSB; greatly increase your SSB “talk power” by
accurately limiting envelope peaks in the SSB modulator. Generate SSB without the
big overshoot peaks that make ALC necessary with conventional SSB modulators.
Watch your wattmeter read higher than before.
Abstract
Achieving simultaneous accurate control
of both amplitude and bandwidth is a
difficult problem. When amplitude-limited
audio is filtered to limit its bandwidth, the
filter may overshoot substantially. It loses
its amplitude limiting ability. If the resulting
overshoots are clipped, the amplitude
is controlled but the signal’s bandwidth
increases because of the clipping distortion.
The signal loses its bandwidth limiting.
Systems exist for correcting audio low-pass
filter overshoot. But single sideband (SSB)
is a more difficult problem, because of
the inevitable Hilbert transform regardless
of the method of SSB generation. ALC
systems reduce the amplitude of an SSB
signal in response to overshooting envelope
peaks. Fast ALC may result in clipping and
splatter. Slow ALC will significantly reduce
transmitted power. This paper presents a
method for generating SSB without system
overshoots. The result is higher transmitted
power without audible distortion.
Objective
One of the reasons for the existence of the
Amateur Radio Service is the development
of new techniques for radio communication.
I hope that this paper will present a useful
method for improving the effectiveness
of SSB transmitters for both amateur and
commercial applications. This technique is
being placed into the public domain and in
particular, the “ham domain.”
1.5
1.0
Overshooting Squarewave
0.5
0
–0.5
–1.0
–1.5
0.0
0.002
0.004
0.006
0.008
0.01
QX1411-Hershberger01
Time (seconds)
Figure 1 — 100 Hz square wave filtered by 3 kHz elliptic low-pass filter.
Benjamin Franklin expressed it well: “As
we enjoy great advantages from the inven-
tions of others, we should be glad of an
opportunity to serve others by any invention
of ours; and this we should do freely and
generously.”
Background
In the 1970s, FM stereo broadcasters’
on-air loudness was affected by overshoot
in the sharp cutoff 15 kHz low-pass filters
(or 19 kHz notch filters) used in stereo
generators of the time. These filters were
necessary to prevent crosstalk between
the left plus right and left minus right
subchannels. As the stereo generator’s
filters would overshoot, the modulation
would have to be reduced to keep infrequent
peaks from exceeding 100% modulation.
A number of manufacturers responded
with systems that controlled overshoot
accurately, allowing a loudness increase
of 2 to 4 dB without any audible increase
in distortion. The overshoots themselves
contained relatively low energy. Eliminating
them resulted in a substantial loudness
QEX – November/December 2014
3

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