|The "ICE BOX"
Small Wonder Labs SW+40 QRP Transceiver Kit
See below - for
the addition of the SOTA Tuner, Elecraft T1 Automatic QRP Tuner as well
as my home-brew "Miniboots" 1-12 watt QRP linear amplifier!
got to build that CW QRP rig I've wanted to try for a while!
What a Christmas present...
QRP is an old telegrapher's term for "low power", which is a past-time
within the amateur radio hobby.
Believe it or not, the weaker radio signals produced by these types of
radios routinely span the globe.
very compact station! The photo on the left was
radio looked like February - The photo on the right shows the completed
radio in April.
Cool! A more recent update to the nearly completed K4ICY Portable QRP Station. (March 2013)
The indicator light on the Miniboots amplifier doubles as a reading light!
Last year I had
the chance to play around with the Pixie II kit. It was a fun kit to
tinker with, but as a direct-conversion single frequency radio with no
selectivity, it lacked many
important features that were needed in a rig that could be
realistically operated. Some folks enjoy them, but it wasn't for me.
Two such features in particular
was a true TX/RX offset, a side-tone and some good selectivity.
If your into
CW, kit building or QRP and have never heard of the SW+40 I suggest
looking at the reviews on eHam
and visiting Small Wonder Labs' site: www.smallwonderlabs.com.
Benson, K1SWL has developed a build-it-yourself transceiver that is
very well developed, compact, and comes with a commercial-grade printed
At only $60 for the main kit, for it's very good
performance it's one of the best deals out there for those hams not
afraid to pick up a soldering iron.
An additional $19 you can get all the external controls, knobs and
sockets required to get the kit operational.
And it only took two weeks to get the kit in hand.
Dave has temporarily removed the SW+ kit from availability. He has
begun a revision process to fix and improve many features.
There are many similar kits on the market that will compare.
• 10.5-14 Volt
Type is Super Heterodyne using a crystal network for filtering
Power has been set to 2 Watts on a 50 ohm antenna load
Frequency Range: Four
sub-bands set within the entire
40 meter (7 mHz) CW Band
Band A • 7000-7034 kHz
Band B • 7032-7066 kHz
Band C • 7061-7096 kHz
Band D • 7091-7126 kHz
Side-Tone and audio bandpass is set at 800 Hz.
Built-in PicoKeyer-Plus Firmware V4.0 ::: 4 text memories, dual speed
"Iambic" Keyer for use with dual paddles, Straight-Key operation
schematic diagram here:
instruction manual (SW+40):
See the Elmer
101 Study Course:
The SOTA QRP Tuner
Purchased as a kit from QRPKits.com
is a tuning device required to electronically match the antenna to the
SW+40, by essentially "tuning" the inductive and capacitive reactance
of the antenna circuit.
This is a mysterious subject to many new
radio enthusiasts, but more information can be had through the learning
material of the ARRL.
While the SW+40 kit from Small Wonder Labs
was impeccably packaged and well organized - I have to state that the
SOTA Tuner from QRPKits (AS WELL AS OTHER KITS) was a different story.
Number one, the
parts for the SOTA Tuner were incomplete, a
.01 uf capacitor was omitted and I was given double order of the 51 ohm
two, the circuit board, when placed in the metal housing provided - did
I had to find a suitable quality capacitor of my own and
I had to file a 1/4" square out of the corner of the board so that it
With that, though, the SOTA Tuner actually works! And
works well. It's really a simple solution that has proven itself
amongst many hams operating on remote mountain cliffs.
These are the parts provided by
the seller (Incorrectly)
This is the first toroid I've
ever wound - not so tough.
Toroid, which is kind of closed transformer or an electro-magnet coil
of wire around a
ferrite doughnut that acts as an inductive element to the
circuit it operates in.
Here it is
soldered to the printed circuit board ("PCB")
little work, the handful of components are soldered to the board.
By this point, I have applied the airplane model stickers to the metal
case and attached it's outboard connectors.
There is a second toroid also shown above.
Here are the main components
installed and wired to form a circuit.
Notice the chunk I had to file out so that the bolt holding the case
halves and it's fastener would fit.
Here is the completed SOTA Tuner
This box will have to be operated in conjunction with the
SW+40 for every use.
The attached wire
is the antenna system for the transceiver.
The antenna wire is "US Navy"-style wound for rapid and easy
deployment. The "Antenna"
side is a 65' wire that is strung to any tree limb. The other side is
the "Counterpoise" that serves as the electrical ground for the
antenna, required for the radio energy to have something to "push"
against when transmitting.
Small Wonder Labs SW+40 QRP CW
Here is the
arrangement for the packaged parts as provided from Small Wonder Labs.
was not used to building large kits, this one has a lot of parts - but
Dave Benson did a wonderful job organizing and packing these many
components into logical groups.
The component soldering and
installation process took ten hours!
were hundreds of contact points that had to be soldered. Each were
trimmed and inspected. The kit included five toroids that had to be
wound by hand.
The multi-VOM meter was used to check for continuity throughout
appropriate parts of the circuit board.
The instruction manual was thorough and easy to work through.
spent several days at my leisure to build this kit and was as
as possible. I chose to follow through the instruction manual for the
Many have used the step-by-step course study online
from Elmer101, going through each stage, making measurements and
learning the intricacies of this radio plus it's theory of operation.
The link to this very informative course is: http://www.qsl.net/kf4trd/lessons.htm
suggest reading through this before building your own. If you are going
to truly experience the fun of operating a QRP rig that you built
yourself, you should understand some of it's basic operation.
completed circuit board was checked and re-checked.
next phase was to connect the control potentiometers (variable
resistors) and run through the manual's procedures on fine-tuning and
aligning the internal circuitry.
The radio will be dead for all intents and purposes, unless the handful
of control parts are tuned properly.
stage, power level was adjusted and filters were aligned.
are two ways to read the transmitter output wattage for final
adjustment. I used a combination of both: First, the instruction manual
describes and easy to build circuit that allows your volt meter to
provide a reading that corresponds to the output wattage. The signal is
converted into a usable voltage for the meter. A basic math formula is
used to convert the voltage reading to watts - and visa-versa.
The second method involves using an HF wattage/power meter to
test the output.
My MFJ-993B will not tune anything under 3 watts input but will give me
a digital reading down to the tenths of a watt.
operation frequency range was determined here too. The SW+40 allows you
to choose operation in any portion of the 40 meter amateur CW band.
stock range of tuning for the VFO (Variable Frequency Oscillator) is a
decent 35 kHz, but this value can be changed as stated in the
instructions to not only make the band as narrow or
wide as the builder desires, but also determine the band's frequency.
I first chose to make this a two-band radio by placing two separate
sets of capacitor banks on a SPDT selection switch.
I added a four-position rotary switch and added two more bands to widen
the tuning range of this rig to encompass the entire 40m band.
disc capacitors called "NP0"'s were used to help prevent temperature
affected frequency drift. These are orange, round and flat with a black
dot painted on top.
They can be found at Mouse.com, and I found a large surplus pack at
This is the
final circuit board which has been mounted in a stock Radio Shack metal
box was only $3, and was the absolute perfect size.
(Moment of Inspiration) Visualization
This picture is not a real
photo, but was first designed virtually in
Moment of Inspiration.
known as "MoI" (pronounced Mow-Eye) it was then
rendered in a rendering program called Kerkythea. Visit MoI
a NURBS/spline-based 3D design and CAD program created
by Michael Gibson, a
The application is very powerful and
accurate, yet easy enough to teach children. I used MoI here
help me solve the common kit building problem of "where to place the
My arrangement looks like it was simply thrown
together, but I spent a few hours moving the computer model parts
around until I was satisfied. Not only did I have the look I
wanted, but that the parts were positioned ergonomically, with the
operation of the radio in mind.
The look, of course being kind of "retro" with a "patch-board" feel to
help you to visualize parts from a fixed or 3D angle and allow you to
move things at will.
I was able,
with MoI, to accurately size components to ensure that they fit inside
of the box too.
MoI's user interface is among
the most simplistic and intuitive of any 3D modeling program.
was now ready to print out the top-view at real-world scale using
CorelDRAW!. I affixed that to the top of the metal housing and had a
template by which I drilled the exact sized holes.
and to the millimeter, every part fit perfectly! (Thanks MoI!)
I used a
Baby Label Maker (common hand-held labeler) to denote each control
is enough room in the bottom of the project box to add an additional
kit or two, such as iambic keying and touch-sensitive paddle
analog dial was affixed.
make the dial, first I taped down a sheet of paper. Then I ran through
a procedure by which I tuned-up into a "dummy load" and using another
radio with a digital readout,
marked the matching frequency on the piece of paper. The paper with the
calibrated marks was scanned and a dial graphic was made in CorelDRAW!.
dial graphic was printed in reverse on to clear inkjet film using an
Epson 4880 printer. The printed image is not waterproof, so a white
spraypaint formulated for adhesion to plastic encapsulated the printed
surface. This surface was on the reverse side, so what I ended up with
was a professional looking plastic label.
Very professional. With this, I have no need for a separate frequency
counter circuit. But....
after additional bands were added, there was no room to denote four
bands of frequencies. A log from 0.0-10.0 is now used as a reference to
a frequency chart.
is complete with out the Morse Code key and a pair of fancy ear-buds.
This is a World War II surplus key used by the Army Signal Corps. It
was passed down by my wife's late grandfather. (XYL's SK)
the Small Wonder Labs "SW+40" QRP CW Transceiver in operation!
The SWL SW+40 Fits inside of a small box and can be carried to any
location. This is PHASE 1.
Continue reading for more pics and continued tweaks......
Future considerations &
• Upping the power output if possible...
I plan on building
With a few adjustments to the base SW+40, I could
just a little over three Watts, but with any output
above 2.3 Watts
the signal output acted erratic, or maybe
frequency instability - None the less, it looks like 2 Watts is the max
for this rig.
There is a power mod presented by KC8AON http://www.angelfire.com/electronic2/qrp/swmods.html
I attempted to try his component value changes but was
The max output voltage was now then limited to 2 Watts. Yes, the signal
but not increasable.
• An outboard audio amplifier with speaker, which would be great for
• An RIT (Receiver Incremental tuning) control.
• Touch sensitive paddle
circuit for eliminating the need for an additional paddle or
• A nice compact sealed
lead-acid battery pack would make this rig more portable.
Consideration for using a different method of frequency selection. At
the moment I'm using a bank of NP0 capacitors on a rotary selector
But I may try widening the bandwidth by
changing C8 on the SW+40 board and replacing the band selector with a
- I added two more bands to make a total of four, essentially
broadening coverage of the whole 40m CW band from 7000 kHz to 7125 kHz.
purchased a 6 position, 2 pole rotary switch from Radio Shack. I needed
only four bands at 30 kHz width each.
I then tried to find a way to modify the part so that it
would only have four positions... After trying different methods,
including trying to add a stop screw,
I discovered that I could move
a stop tab on the spring leaf that allows the switch to rest in each
detented position. I was able to bend it temporarily over the a stop
and the part was essentially reversed. Now with the spring leaf tab
caught on the reverse side of the stop tabs - I created a 4 position
Consequently, other mods can be made to that type of rotary switch
yielding other combinations including a 12 position version!
was then able to bank clusters of matched picofarad capacitors to each
of the posts. Matching was not absolutely perfect, but 99% access to
the band with a good amount of precision ain't half bad.
02/24/12 - Completed a Tayloe Battery Status Indicator from Hendrix
Kits. It has an LED that changes colors based on voltage
With this, if the indicator is green then I know I am
getting out full wattage. If it is orange, then I'm working on borrowed
battery life. If the light is red, then I should shut down and
re-charge the battery, since proper operation of the radio cannot be
• 02/26/12 - Completed trial on using a 1k potentiometer
to attenuate the AF output - thus protecting my ears with strong
• 02/28/12 - Completed constructing and running initial
tests on a KD1JV Digital Dial / Frequency Counter with 4-digit LED
I still need to calibrate the DDial and set the offset
parameter, but this promises to give my full-band QRP radio an accurate
tuning dial and provide more enjoyment of use.
02/28/12 to 03/31/12 - PHASE TWO REVISION ON THE SW+40. Now called the
"Ice Box" for fun, it is a very sleek looking rig with many new
Added an "AF Gain" control (Volume) to the
audio. Strong signal were tough on the ears, but now are controllable
using a potentiometer right at the output.
At the moment I am using a 5k ohm
potentiometer but it is too large and I'll put a 1k in there soon.
Added and finalized the KD1JV Digital Dial. My computer
positioning did not take into account the sized of the Radio Shack
I hand-filed each stand-off down to
0.3" in height and shaved 0.2" off of the sides of two so that the case
could be closed.
I had an older digital alarm
clock that was put out to pasture. It has a red diffusion sheet that
has adhesive on it which I used for the LED display.
Added a Pico-Keyer Plus, or actually purchased
just the chip and used a prototype board to build it's circuit.
Added a Tayloe Battery Status Indicator to tell me
when the input voltage in under an acceptable level.
With this, just to be cool, I replace the ugly
orange/green LED with a Full-Color LED. Since it's common pin
arrangement was the anode type instead of the
cathode type it was designed to operate, I used a couple of
transistors and a few resistors to get my K4ICY signature color
arrangement of aqua, white and red.
A new case was needed... This time I took care of
design the arrangement of the controls for logical usage.
The tuning knob has a clear berth and there is
for the Digital Dial. The jacks and connectors were placed on the sides.
A clean coat of aqua colored spray paint finishes
Yes, I made a rectangular opening for the dial.
RG-174 Coax was used to make runs for some of the
more RF/Capacitance sensitive connections.
04/10/12 - Moved the PicoKeyer-Plus audio line from the junction of
R9/R10 on the SW+40 directly to the headphone audio hot side.
Bypassing the filter capacitor through a single
electrolytic. Eliminated the key-down "Chunking" issue cause by its
Audio filter is not really necessary
since the tone is only present on PK+ menu selections.
• 04/11/12 - Added a 1.5 Mega Ohm resistor from pin 3 of the
PicoKeyer-Plus chip to circuit ground.
There was a initial key-down and activation of the
transmitter upon the rig's power-up that would last a split second.
This was due to a lag in power availability to the
chip as other circuits in the rig were also powered up.
The keyer control MOSFET was left momentarily
the resistor acts as a "pull-down" stabilizer to keep the gate turned
off until the PK+ sends a positive signal.
Generally, the PK+ is designed to run off of a continuos
battery supply voltage, but in this case, it feeds from the rigs
external power source, which takes a bit to begin feeding the other
area of the rig, especially larger capacitors.
04/12/12 - Added a small filter circuit to the positive power lead of
the Digital Dial. My attempt was to reduce the digital has noise
created by the dial's multiplexer.
I used a
resistor, electrolytic capacitor and a small choke. However, after
adding this mod, I only noticed a very small reduction in noise.
Unless I place the digital dial in a Faraday Cage
box that is grounded), there are too many other leaky sources of noise
and pick-up inside this crowded rig.
TWEAKED THE TUNING
SELECTOR. The frequency range was first set to cover an optimum 7000
kHz to 7125 kHz, when I installed the parts in the enclosure, some kind
of capacitance was added and shifted everything down from 6xxx kHz to
7119 kHz. This was bad. The RG-174 coax cable that connected the
selector bank to the rig was adding capacitance. FIXED! I
only 1.5" from the cable and the band frequency range magically went to
7001 kHz to 7126. Really?!?
We can safely say that an inch of RG-174 is
enough to move the rig's operational frequency 20 kHz!
suggestion to anyone trying to tailor their frequency range on the SW+
::: Set the bandwidth as wide as you need with a single value NP0
capacitor directly to its contacts on the circuit board, and do the
tuning and band selection with banks of resistors and potentiometers.
Those are stable since the VFO is controlled with voltage at
part of the circuit. Will I plan to change over to this
probably not since I have my frequency specs close to accurate with my
01/13 - Visited the shack of ham friend, Norm, K4GFD in Greensboro, FL.
I was getting bad harmonics from the signal of my SW+40, so
connected it to a very complex looking spectrum analyzer with all kinds
of bells and whistle. It has a built in dummy load and
attenuator. We discovered that the SW+40 was pushing nearly 5
watts on peaks! However, this came at a sacrifice of signal
quality. The final transistor in the SW+40 was getting pretty hot as
well. After some adjustment, including the power-level adjustment in
the SW+40, we determined that it was set way too high. Once we brought
it down, we were able to peak the output to a very pure 2 watts with
little harmonic artifacts. I would like to note that if you
choose to use the "volt-ohm" meter method as described in Dave's
instructions, you'll not be able to see if any of the signal is being
wasted before the final transistor amplifier due to inefficiency. One
the final amp transistors are pushed beyond saturation, you may have a
stronger signal, but it will create excess heat and splatter all over
the band! Do not consider these tweaks offered by other
claiming that more power is yours by modifying the circuit.
you are really proud of the time and effort put into a fine transceiver
kit such as this, you'll demand nothing less that 'quality' over
03/03/13 - Completed a multi-feature version of the NB6M
"Miniboots" QRP-Gallon amplifier: http://www.amqrp.org/kits/miniboots/miniboot.htm
The Miniboots is an outboard RF amp based on the inexpensive
IFR510 (readily available at Radio Shack) that can
take 1 watts from any QRP rig and boost the output up to 12-14 watts
(at 14 volts).
A relay controls the transmit/receive with an RF sensing
so the mode of CW operation is semi-QSK. After a month of
experimentation and building, I now have a linear amplifier and a
controllable final power output from 0.1 to roughly 12 watts!
the Miniboots amplifier requires only 1 watt input, I was able to
reduce the output setting within the SW+40 to less-than 1 watt.
The Miniboots comes in two configurations, one with a
step-up/impedance matching transformer and one the other with an
attenuation resistor pad depending on whether you have a QRP (<5
>1 watts) or QRPp (< 1 watt) rig.
More info and pics soon!
• 03/14/13 - Completed building the Elecraft T1 - Automatic Antenna
Tuner. This tuner can tune HF-6m with an input of 0.5 watt to
20 watts. It took me five nights to build. It's very compacts and
stuffed to the gills with 15 micro-mini latching relays and nine toroid
assemblies. I was surprised myself when it actually worked
and so far I've used it on my SW+40 as well as my Yaesu 857-D at 15
watts. The T1 also gives information on SWR and power output.
(SEE PICS BELOW)
is a finished PicoKeyer-Plus from Hamgadets.com
PicoKeyer-Plus is a very compact device that provides iambic keying
"dits" and "dahs" from your side paddle to any radio originally
work with a straight key.
It is also comes with four programmable keying text memories as well.
For only $18, it is very easy to construct this kit and is rated by
Hamgadgets to be at a "beginner's degree of challenge".
will also run independently for months if not a year from a standard
coin-type lithium battery, and can handle up to 60 volts of positive
keying in your radio.
I ordered this kit not for the inside of my QRP rig but as a
stand-alone to operate radios such as my Kenwood TS-130SE.
It also makes for a great code practice oscillator for using a paddle.
It will also auto-detect a properly wired straight key and will
automatically switch to straight key mode.
This is the keyer installed in
its attractive plastic case.
For $8 you can get a plastic case that has all of the holes pre-drlled .
Here is the completed Phase
modification or two has been added: The entire 40m CW band is now
accessible with the help of the rotary capacitor bank selector switch.
The paired PicoKeyer-Plus allows for iambic keying.
to implement PHASE 3 :::
is the N7VE Tayloe Battery Status Indicator Kit.
Another fine kit from Hendicks QRP Kits at qrpkits.com.
circuit Illuminates a Tri-Color LED according to user-determined
voltage level thresholds. You can also illuminate separate LEDs if you
In my case, I'm using a Full-Color LED purchased from Radio
Shack allowing me to light it an aqua color to indicate a good supply
voltage level of
The LED shines white when the level starts to drop below
12 volts, and becomes red when the voltage drops below 10.5, at which
level, it would not be advisable to operate the SW+40's transmitter
section. The circuit is designed to use an LED with a cathode
common, but the Full-Color LED ties its red, blue and green sections to
an anode (+) common. Thus, I had to use the BSI to turn on a couple of
NPN transistors configured to drive LED's. Those were used to then
control the elements in the
board is tiny, so I actually soldered it to the prototype board along
with the PicoKeyer+Plus using expelled component leads as board traces.
not fear learning how to use transistors to do your bidding, there are
kits, manuals, courses and online information to help you learn.
is the BSI circuit under test.
used a potentiometer to "dim" the voltage to the circuit triggering its
threshold levels determined by trimming potentiometers on the board.
tricky part of not using a controlled voltage supply was dealing with
the swings in voltage caused by current changes from the activation of
the LED segments.
But I made it work.
This will be
the sub-board under construction.
This prototype board was used to incorporate the PicoKeyer-Plus, Tayloe
BSI, audio matching and other minor circuits.
3D put to good use again!
this simple yet powerful 3D CAD tool, I was able to work out both the
functional ergonomics and the exact placement of the "Ice Box's"
controls and components.
Since so much more was to be stuffed into the small project box,
component placement had to be right on the money.
I had to take more care this time to get and accurate
representation of the exact sizing and proportion of each major part.
was able to make mistakes and revisions in the "virtual world" first
before work was done.
actuality, there are always unforeseen details, and objects are always
smaller on the screen than in real life. I would run into slight
From MoI 3D, I exported an .AI file of the top-view to be brought into
CorelDRAW! for printing.
There was really no way to make a mistake with measurements because the
printout was "life size".
method for creating the holes for components involves first drilling
with a 1/16" drill bit. Second, increasing the drill bit size until the
final diameter is met. And third, using an array of metal files to
fine-tune and de-bur. The rectangle hole for the Digital
was not that hard to manufacture. (No, there is no such thing as a
square drill-bit) A large hole was made in the middle
and metal files were used to "square out" the remaining area. The
aluminum in the Radio Shack project box is very soft.
is the final drill and file work.
Thanks to the template, the drill-work was accurate to the 100th of an
enclosure ready for components.
test fitting was made with the components and minute adjustments were
made. The enclosure parts were then sanded with fine-grit
and painted first with a primer and then a few coats of the colored
spray paint of my choice. This color is Krylon's Blue Ocean
Breeze, a nice light aqua color reminiscent of the color used by some
old Volkswagen Beetles and vintage appliances.
steps to make it to this point were many. This was the culmination of a
month of work. The large board in the bottom half is the Small Wonder
Labs SW+40. The small board in the middle-top of the top half is the
Digital Dial and the prototype board is affixed to the side of the case.
As you can see, the SW+40 PCB was offset to accommodate placement of
the prototype board.
management was my largest tackle. I ended up with redundant ground
wires and I am also left with an uncertainty that a few wires may be
free to be too close to function correctly in RF transmission
situations. This problem would become apparent later as installation
closer view of the component placement.
of the components landed where they were intended. A large obstacle
were the stand-offs for the Digital Dial. I spent a good day filing
them down to exact dimensions.
is the final station setup for the new "Ice Box" QRP CW station!
completes PHASE 3.
paint job came out nice, and the aqua-colored LED is a nice touch.
Yes, the paint will chip and scratch easy. Only
could make for a resilient surface.
The voltage indicator using the LED works well, as does the band
switch. The Digital Dial is also accurate to 100 Hz.
close up of the KD1JV Digital Dial.
Here is a close up view of the KD1JV Digital Dial available from
Hendricks QRP Kits at qrpkits.com
kit is NOT for the faint of heart! The majority of the parts
including the 20+ pin microprocessor chips are SURFACE MOUNT and half
to be soldered to the sub-straight with either SMD past and heat
methods or a very small solder. I used 0.15" diameter silver-bearing
solder found at Radio Shack. Though I have to say that the sales clerk
said that it was not on in the system and couldn't figure out why they
had it. Their smallest was 0.22", but that will work too.
diffusion lens was found on a discarded digital alarm clock. It was
adhesive and peel right off of it's original clock display.
the stand-offs were filed to an accurate height, the Digital Dial's LED
display sat just below the opening with enough clearance for the red
notes for connecting the KD1JV Digital Dial to the Small Wonders Lab
instructions for the Digital Dial don't go into much detail concerning
how to get this thing to work with any particular QRP rig on the market.
is NO place on the SW+ board for getting an IF signal, that will not
only provide a good frequency to subtract from the VFO frequency, but
since the IF in the SW+ is crystal controlled, you cannot change it by
the 800 Hz + which is the offset of the VFO. Even if you
the 4 Mhz signal reading from the VFO, the resultant display reading
will still be 800 Hz above the transmit frequency. The transmit
frequency is the number you want on the display.
By the way, the place to connect the signal lead
from the Digital Dial is at PIN 6 of U1
(First RX Mixer), the SA612 - or any circuit trace on the board
directly connected to pin 6. Use the provided 5 pF blocking
capacitor provided, one end connected to pin 6 and the other to the
cable's center lead.
Use small coax
like RG-174 and tie the shield ground to any nearby ground terminal on
the SW+ board.
program the IF Offset - There is no need to connect the signal sense
lead to anywhere else on the SW+. Short out the two pads on
Digital Dial marked "SW Offset" to enter the IF programming mode. Click
the Mode switch on the other side until the "LO - b"
appears. This tells the DD to give a reading that is VFO - IF.
the SW+40 VFO until the frequency of (7)"000.8" is displayed. This is
7,000.80 kHz. Click the Mode button and keep it held closed until the
Now the offset of 7000.8 kHz
has been programmed in and it will be subtracted from the true
frequency reading giving you the correct operating frequency reading.
below 7,000.00 kHz will give a strange reading. You don't need to go
when pressing the mode button to go to the Mhz display mode, the
display will give a strange reading. Since you are using a single band
rig, there is no need to see the "7". I
simply chose not to install the mode switch accessible through the
control panel. A pushbutton with a tall tab is provided, but since it
is not needed, either solder it underneath the DD's board or put a
switch with a different orientation as I have.
also suggest to install the following parts to the opposite side of the
board from which they are in the instructions: The mode
the electrolytic capacitor and the trimming capacitor. If you're going
to mount the dial to the underside of a panel, placing these items on
the opposite side where they can be better accessed will prove useful.
is a close-up view of the prototype board that houses the
PicoKeyer-Plus, the Tayloe BSI, the LED control circuit, and other
The resistor soldered to the bottom is the 1.5 Mega Ohm "pull-down"
stabilizer resistor for the gate of the keyer 2N7000 MOSFET.
the logic circuits within the PIC PK+ chip are enough for on or off
operation of the 2N7000's gate, but the power availability of the rig's
power to the chip is initially limited and available power is ramped
up. The added resistor eliminated the problem of the transmitter going
into temporary key-down when power is first provided.
is a small 100uF electrolytic capacitor which provides audio with DC
blocking to the PK+'s audio out to be fed to the receiver's headphone
The PK+ provides it's own side tone, but this is disabled through it's
programming menu since the SW+40 already provides it.
since the PK+'s menu/programming system works with an audio response,
those sounds must still be audible. Audio quality of the menu tones is
not critical, of course.
THE "MINIBOOTS" QRP LINEAR "GALLON" AMPLIFIER
I started the "Miniboots" amplifier project "dead-bug" or "ugly" style on a copper-clad PC board.
This circuit is based on the NB6M "Miniboots" design, no longer in production as a kit.
allowed me space to alter parts where needed. The heart of this
QRP-level "Gallon" linear amp is based on the cheap and readily
available IRF-510 power MOSFET.
Toroid cores were ordered from
Amidon Inductive, Inc. The resistor wattage types were chosen to
handle the initial two watts input through an attenuation 'pad'.
Eventually, the drive level in the SW+40 was curbed to 0.7 watts,
ensuring that the final transistor in the SW+40 would run more
efficiently. The resistor attenuation network ensures that the
SW+40 finals see 50 ohms of impedance!
The "swamping" (or biasing)
resistors at the gate of the MOSFET are 2x2 stacked 1/2 watt types
which together reduce the effects of heating. This may not be
needed, but it was worth trying.
The main issue I had was tweaking
the low-pass Chebychev filter on the final. The input impedance
from the MOSFET varies with both temperature and frequency, but it is
around 7 ohms. The output is of course 50 ohms. I tried several
models using the AADE Filter Designer software until I came up with one
that gave me roughly 12 watts at a source voltage of 13.8 volts, while
also staying well within the limits of FCC rules on harmonic
suppression. However... the crux of packing anything dealing with
RF into a small metal box is that now I have strange capacitances to
deal with and as of this posting, my output maxes out at 6.8 watts.
I should be able to lower the inductance on at least the initial
toroid to see some improvement. None the less, I'm at my 5 watt
Here is a closeup view of the final portion or the "Miniboots" amp.
The IRF-510 (in its TO-220 packaging) got extremely hot even with this clip-on heatsink.
After I was satisfied with the results, I added the relay which was controlled by an RF-sensing circuit.
I had a chance here to play with the capacitor value that would determine the 'Semi-QSK' dwell time.
Proof of the "Miniboots" linear QRP amplifier in action: 0.7 watts in - 12 watts out (at 13.8 volts source).
Now the tested circuit was altered for a more compact fit inside of this high-quality aluminum enclosure.
Drilling, filing and fitting were the most time-consuming process in completing my version of the Miniboots amplifier.
large knob is for attenuation control that chooses an output level from
1 to 14 watts (when finalized). Control emphasis was placed on
the 6 watt and below range using a non-linear pot configuration.
Also in the front is the control switch and status LED.
control switch not only controls power to the amplifier circuit but
routes the input RF line to a 2-watt dummy load to help protect the
SW+40's finals from accidental keying.
The LED is again, a K4ICY
custom! Using the small breadboard circuit (to the left), the
Full-Color LED shines a very bright aqua color when the amplifier is
powered up and in standby mode, then shuts off and shines red for every
keyed RF signal. An SSB signal would show a more varied
fluctuation in the red signal. Once keying is stopped, the aqua
light waits a little bit so that you have a more visual indication of
your sending, then slowly re-lights. A nice N-type power
connector is on the back, powered with a 6-amp laptop DC cord.
BNC female RF connectors are on the sides.
Click on this pic for a larger view... You can see the
relay (on the right) that has hot-melt glue on top as it presses
against the enclosure lid.
On the far right is the dummy load
array (2 watts). The LED status board is on the far left and every nook
and cranny has been stuffed with the amplifier and RF sense circuits.
THE ELECRAFT 'T1' MINIATURE AUTOMATIC ANTENNA TUNER
Here is shown the kit-building process for my new Elecraft "T1" Automatic Antenna Tuner.
kit was too expensive to be included within the case of an amp or QRP
rig, and frankly, I don't recommend building this, but rather
purchasing the unit in completed form. It's tolerance are almost
too tight for the actual parts supplied and there are simply too many
potential points of failure. I enjoyed building this kit however,
but there were too many 'scary' moments. However, it worked right off
the bat! I recommend using an even thinner solder diameter than
specified. Construction took five nights to complete.
Here is the final product. This thing is tiny indeed - about the size of a pack of cards.
would have preferred to build a traditional Pi-network LC manual L/C
tuner and I may someday, but having an instant match without risking
the death of a QRP rig's fragile finals is fine with me.
Here is my complete portable QRP station (for 40 meters) set up on a table on my back patio.
the top is a 3.3 ah SLA gel-cell battery, to the left is the T1 tuner,
the completed Miniboots amp is in the middle, and the SW+40 to the
are still issues to resolve!!!
is a digital hash noise from the Digital Dial. It has to be a good S3
in audibility. I have read to expect this as it might be coming through
the power-supply line, and there are methods already tried by
remedy this problem. So far, my attempt at filtering has produced no
• Other improvements and
fixes involve changing the audio volume potentiometer from a 5k ohms to
a 1k ohms or less.
Experimentation with a single band opened wide with a pair of highly
stable capacitors, using two potentiometers to hone-in on a more
precise and stable frequency.
One op I had a QSO with noted an
abrupt frequency shift, but I believe a faulty antenna cable was at
fault. which points to some kind of affecting capacitance on the
The output low-pass filter on the Miniboots amplifier needs to be
modified to realize its potential 14 watt output. Though 5 watts
is the target for QRP, more is welcome sometimes.
than a few minor remaining issues - I'm very satisfied with the results.
do not plan to immediately continue development on the "Ice Box (Phase
3)", with the exception of adding labels or screen printed markings.
The box has now been closed and I plan to take it into the field and
work some QRP slow-speed CW.
seems to have come together well with this project and the integration
of these many kits are a testament
to the ingenuity of their creators.
Special thanks to the kit creators and vendors for their helpful
correspondences and technical support :::
Dave Benson K1SWL
- Small Wonder Labs / SW+40 CW Transceiver Kit - smallwonderlabs.com
Dale Botkin N0XAS
- PicoKeyer-Plus / Iambic Memory Keyer - hamgadgets.com
Steve Weber KD1JV
- Digital Dial / Frequency Counter - qrpkits.com
WA1JOS - CW Touch Keyer - cwtouchkeyer.com
plan on having lots of fun furthering my learning of CW and making
building is a wonderful pastime, and learning basic electronics (even
if intellectually) should be a right of passage for all "hams".
DE K4ICY SK ••
Go build you own!
©2013 Copyright - Michael A. Maynard