April 28, 2015
with the Small
Wonder Labs SW30+ Transceiver
Understand the basics of this
classic monoband superhet ... and build up the kit here with us all in
successive episodes of CWTD!
kitting of the classic 2-watt monoband superhet transceiver
designer Dave Benson K1SWL of Small Wonder Labs.
Welcome! In this
episode we are kicking off the first string of monthly CWTD
programs that focus on “Elmer 101” instruction and guidance as many of
us build up the resurrected SW30 superhet transceiver kit originally
produced by Small Wonder Labs some time ago.
Many great instructional references
were published several years ago and we’ll be paralleling portions of
each as we ramp up CWTD participants and podcasters on the theory and
design of the project, while stage-by-stage building Dave Benson’s K1SWL
classic little 30m kit. (A limited run of the SW30 Kit is being done for
CWTDers, with permission and assistance from K1SWL.)
Sure hope you can join us as we
start by exploring the basics of radio design in this series … and then
reach for the stars!
73, George N2APB and Joe N2CX
Listen to the Podcast
and download to your computer for best listening results)
Elmer 101 and the SW30 Transceiver
Elmer 101 - Learning Theory for Fun
... from the web pages of Jim Larsen, AL7FS ...
In the early days of winter 1997 - 1998, there were QRP
Operators on the QRP-L Mail List that were wanting a fun transceiver
project that was more than just plugging in parts on a board. They
wanted to learn from the experience and they wanted to help other hams,
new and old, to learn the theory behind the QRP transceiver. A general
call went out to the list for knowledgeable hams to act as Elmers (Elmers:
Hams who help hams or prospective hams with technical or other issues)
for the building of a 40 meter QRP CW transceiver.
One of the exciting aspects of the QRP-L Mail List
(information near the end of this article) is that a large number of
the people that you have seen writing articles (for ham radio
magazines) over the years hang out on QRP-L. These technically savvy
hams raised their collective hands and volunteered to author course
material for the building of a transceiver. In the end, the primary
authors of the SW40+ overview and course details were Mike Maiorana
KU4QO (ex. KF4TRD) and Glen Leinweber, VE3DNL. The course was dubbed Elmer
The only thing left to do was to decide on which QRP
transceiver kit would become the centerpiece of the Elmer 101
course. After much interesting discussion on QRP-L, Dave
Benson, NN1G, of Small Wonder Labs, offered to update and
improve his already well-known classic SW40 CW QRP transceiver. (The
SW40 design was published in the November 1994 issue of QST and
serves as a centerpiece in the ARRL's anthology, "QRP Power".)
circuit and thus the PCB (printed circuit board) were upgraded and
the kit was offered at $50 (currently $55 (postpaid) to US) (Did not
include the cabinet and chassis mounted wiring and parts) for the
class members. This tiny little 2-watt CW transceiver had already
proven to be a real performer and now it was even better. The rig
was renamed the SW40+.
Elmer 101 began
with a list of prerequisites for each prospective "student" to study
as preparation for the actual course. Then, slowly, at a pace geared
to allow each student to build and learn, the course unfolded.
I was fortunate to be subscribed to the QRP-L mail
list during the development and rollout of the Elmer
101 course. I had
been a ham operator for over 32 years, had passed my Amateur Extra
Class tests, but in spite of all this opportunity, I still did not
understand the inner workings of a modern day CW transceiver. This
approach to learning was to be one of the most exciting periods of
my ham career.
The prerequisites had me actually reading and
studying from the ARRL Amateur Radio Handbook. This material kept me
plenty busy as I ordered and waited for delivery of my Small Wonder
Labs SW40+ kit. By the time the kit arrived I was ready to begin
studying each chapter of the Elmer
101 course. The basic
approach was to read the theory, relate it to the schematic and then
build and test that section of the transceiver.
The beauty of this course was that if you got stuck
or needed help in any way, you could ask the question to the entire
QRP-L Mail List group. Always, the answer would be posted in terms
designed to help each student grow. (This help is still there
Day-by-day and week-by-week, the theory began to grow
in my head. The transceiver grew section by section. The transmitter
section was scheduled into the process such that it could be used to
test the receiver sections. Gradually, the mystery of a CW
transceiver was reduced to such a level that I could enjoy looking
at a schematic without getting too frustrated. I had finally learned
theory and married it to practice.
Today, the Elmer
101 class is
complete. Many SW40+ transceivers have been built and are now
operating on the air. This little rig from Small Wonder Labs is
available in mono-band form for 80, 40, 30 and 20 meters. While I
built mine for the class target band of 40 meters in the Elmer
101 course, I think
the 20-meter version would be especially useful for hams in Alaska.
This rig costs only $55 postpaid in the US. You can provide all your
own chassis parts and chassis or an enclosure kit (shown above with
customized labeling) is also available at $35 plus $3 shipping and
comes with all harnesses, connectors and controls. As discovered on
my business trips to the Lower 48 states, it is a real performer. I
have had successful contacts right from my hotel room with a
long-wire antenna dropped out of the window.
info on the circuits ...
& SW-xx Building Resources
101 web page.
"We have separated the construction of the SW-40+
kit into functional blocks.
Each part is posted to the QRP-L list and then discussed online.
Below are the links to the different sections archived."
Elmer 101 Special Issue,
QRPp magazine from Autumn 1998 ...
Starts at page 140 in this large PDF download.
87 pages of assembly guidance, background and theory!
The Eks Files ...
Chuck Adams, K7QO did his usual excellent
homebrewing and construction renditions with this version of his
build-up of the SW30 Kit.
... available for download at Chuck's site ...
Labs "SW30+" Kit
not supplied in this kitting round)
Here's the overview of this
family's design features:
- Single-board transceiver,
2.8 x 4.0" (7 x 10.1 cm)
- Commercial-quality board,
masked and silkscreened
- True VFO: 35-40 khz coverage
[SW30: 10.1-10.135 MHZ]
- Superheterodyne design, with
- Quiet solid-state T-R
- Output Power Adjustable-
Uses straight key &
filter at 4 MHz
Kit uses all
“add-ons”: keyer, RIT, frequency display, and more.
$45 (approx, plus shipping) ... only available through CWTD.
[Ordering details to be posted May 1st.]
The SW+ series retains much of the
original "40-40" receiver design, while augmenting the transmitter
design for improved stability and output power. The following design
changes went into making a classic even better:
- Added power supply
- The number of toroids to
wind drops from 8 (in the original) to 5. This pays off in
faster and simpler assembly.
- The diode bridge T-R switch
is replaced by a series L-C type. This drops receiver
current draw from 22 to 16 mA and improves image rejection.
- The crystal filter is
changed from 2 to 3 crystals for improved skirt selectivity.
A grounding point for the crystal cases is also provided to
reduce filter 'blow-by'. For the 30M version, the IF has
been changed. This relocates the image response to virtually
eliminate SWBC pickup.
- Replaced a number of local
oscillator components for improved reliability and
- The PA is a T0-220 device,
capable of more output power than the original. Should you
wish to modify the design slightly for more power, there's
now space for a TO-220 heatsink.
- The interconnects have been
functionally-grouped. The board kit-only builder may wire
directly to the board in convenient wiring groups. The
companion enclosure kit provides locking .100" headers, with
pre-assembled harnesses. The new board is 'drop-in
compatible' with prior versions of the SW-series enclosure
- The printed-circuit board is
now double-sided and solder-masked both sides. Component
silkscreening is improved, and all parts are identified on
the silkscreen by both outlines and reference designators.
Theory of Operation
SW30+ Manual ...
Next Episode ... Opening the kit and
Organizing/Identifying the Parts! ... May 19th