My Small Wonder Labs SW+40 QRP Transceiver Kit  (and accessories)

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Use this Quick-Menu to 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!

NOTICE:: The ME40+ now supersedes the SW+40

Rick Choy, N3HXT, at Midway Electronics in Middletown VA has taken on Dave Benson's SW+40 and is now again available for sale, now called the ME40+!   Rick has spiffed up the original manual to have a "Heathkit" style to it and offers the kit in 40, 80 and 30 meter versions with 20 meter version on the way.  Visit or contact Rick at for more details.  You can order the MExx+ on eBay as well as Rick's website.


[circa 2012]  Well... I finally 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!

QRP Station SW+40  The "Ice Box" QRP CW Station

A very compact station!    The photo on the left was what the radio looked like January 2012 - The photo on the right shows the (partially) completed radio in April 2012.

K4ICY Portable QRP Station at Night   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

[Update summer 2012-2013 -  Dave Benson stated that he was retiring and halting all sales of kits including the famous "Rockmite"]
[Update - Small Wonders Labs has shut down permanently]

Dave Benson, K1SWL has developed a build-it-yourself transceiver that is very well developed, compact, and comes with a commercial-grade printed circuit board.
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.

• 10.5-14 Volt operation
Receiver Type is Super Heterodyne using a crystal network for filtering
Output Power has been set to 2 Watts on a 50 ohm antenna load  [March 2013 - Output set to 0.7 watts to drive the Miniboots 1-12 watt amplifier]
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 (5-60 wpm)
"Iambic" Keyer for use with dual paddles,
Straight-Key operation automatic.

See the schematic diagram here:

See the instruction manual (SW+40):

See the Elmer 101 Study Course:

To start off, I ordered a miniature QRP tuner as to match my future SW+40 to its antenna.
Rumor has it that the final transistor in the SW+40 is not only sensitive and prone to blowing - but is obsolete and extremely rare to obtain.

The SOTA QRP Tuner  Purchased as a kit from (eHam review)

This 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 resistor set.
Number two, the circuit board, when placed in the metal housing provided - did NOT fit!
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 would fit.

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.

QRP Kits SOTA Tuner Parts  These are the parts provided by the seller (Incorrectly)

Winding the Toroid for the SOTA Tuner   This is the first toroid I've ever wound - not so tough.

The 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.

SOTA Tuner PCB   Here it is soldered to the printed circuit board ("PCB")

SOTA Tuner Kit   After a 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.

SOTA Tuner Kit Construction   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.

SOTA Tuner   Here is the completed SOTA Tuner kit.

This box will have to be operated in conjunction with the SW+40 for every use.

SOTA QRP Antenna Tuner   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 63' 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.

Update: [01/11/14]  Upgrade for SOTA Tuner Terminals

Frankly, the thumb-screw (wing-nut) arrangement designed for antenna connections to the SOTA Tuner outright sucks!
They were prone to coming loose, even during transmit and even after I tried lock-washers on the eye-lugs side, and on top of that, as I use one set of wire for different tuners (see the Elecraft "T1" below) unscrewing the thumb-screws were a pain.

For the life of me, why in the heck didn't Hendricks QRP Kits not spend the extra two bucks to use banana-type terminals... I mean, c'mon man!

Well, problem solved, and I suggest anyone building the SOTA Tuner, which by the way, actually works great, should consider installing the better terminals in place of the wing-nuts!

Radio Shack Banana-Terminal Replacements   Shown here is SOTA Tuner and a new pack of "Banana Jack Insulated Binding Posts" RS# 274-0661

Radio Shack sells these great banana-terminal posts for a couple of bucks which seat in with a small bolt and is able to not onle accept "banana" spring plugs, but can screw-tighten spade terminals.  An additional hole is available to hold bare wire ends.

The SOTA Tuner uses a pair of nylon insulator washers to separate the terminal bolts from the chassis, so I'll re-use those, and you should be able to also use the terminal tabs soldered to the circuit.  The only more complex task you have to do here is removal of most of the parts in the tuner to access the terminal bolts.

Hardware disassembled   Here is the disassembled hardware.

After the tuner's components were un-affixed and moved aside, the original wing-nut assembly was taken out, go ahead and leave the nylon washers in place.

Install the new terminals   New terminal held in place as hardware is installed

I temporarily removed the cap from the new banana terminal and a very small screwdriver (or nail) is great for holding it in place as you attach the original circuit connection terminal lugs to the back.  I used the pre-existing insulator but added the provided paper washers.

Terminal detail   Detail of the installed banana terminals

Here you can see that I used the original terminal lugs but added the new ones along with the originals as they had a smaller hole that matched the new smaller terminal bolt's diameter.  I also used the original lock-washers as well as the second nut - that way, the new terminals will be less likely to come loose.   It's a good idea to test the antenna-side terminal for accidental continuity to the chassis.  It's not necessary for the "counterpoise" side to be isolated as it is already grounded, but it looks nicer to have the terminals sit at the same height.

Quick-Disconnect Antenna/Counterpoise Terminals   New Banana-Terminals Installed

The new terminals are ready for QRP service!  Not only can the antenna line and counterpoise be connected in a pinch, but allow for an emergency disconnect if the wire is say - unexpectedly pulled away by a wind-driven tree-branch, or worse, an unaware passerby!  Yes, both have happened more than a few times with the SOTA Tuner ending up on the ground. (and diningroom floor)

The Small Wonder Labs SW+40 QRP CW Transceiver Kit

SW+40 Kit Parts   Here is the arrangement for the packaged parts as provided from Small Wonder Labs.

I 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.

SW+40 QRP Kit Construction   The component soldering and installation process took ten hours!

There 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.

I spent several days at my leisure to build this kit and was as meticulous as possible. I chose to follow through the instruction manual for the construction process.
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:

I 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.

SW+40 Alignment   The completed circuit board was checked and re-checked.

The 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.

SW+40 QRP Alignment   At this stage, power level was adjusted and filters were aligned.

There 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.
[Update!]  See Tweak below done on 01/2013... The instructions for Dave's RF voltmeter circuit were somehow off!  The output was set too high and caused problems.
For a concise method of measuring RF voltage without a real wattmetter - please see my Weekend Radio article in The Printed Circuit - Newsletter of the Tallahassee Amateur Radio Society for April 2014 - Page 14  [Click Here for Article]

The second method involves using an actual HF wattage/power meter to test the output.
My MFJ-993B will not auto-tune anything under 3 watts input but will give me a digital reading down to the tenths of a watt.

The 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.
The 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.
A note of caution here: widening the band range will sacrifice selectivity, but you can bank smaller widths to get more range without sacrificing quality...

I first chose to make this a two-band radio by placing two separate sets of capacitor banks on a SPDT selection switch.
Later, 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 CW band!
NOTE: A standard 10-position rotary switch from Radio Shack, by removing or inverting the position of its stop tab can easily be converted to either a 4 or 12-position switch!

Ceramic 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, and I happened to find a large surplus pack at Radio Shack.

SW+40 QRP Kit   This is the final circuit board which has been mounted in a stock Radio Shack metal enclosure.

SW+40 QRP Kit   This metal box was only $3, and was the absolute perfect size.

Moi (Moment of Inspiration) Visualization
   - Using a CAD program to accurately engineer a homebrew project...

MoI SW+40  This picture is not a real photo, but was first designed virtually in the CAR program: Moment of Inspiration.

  Visit Moi3D at

Moi3D is a NURBS/spline-based 3D design and CAD program created by Michael Gibson,
a one-man team.
The application is very powerful and accurate, yet easy enough to teach children.  I used Moi3D here to help me solve the common kit building problem of "where to place the controls".

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 more ergonomically, with the operation of the radio in mind.
The look, of course being kind of "retro" with a "patch-board" feel to it.

MoI SW+40 Layout   Moi3D's views help you to visualize parts from a fixed or 3D angle and allow you to move things at will.

MoI SW+40 SWL   I was able to accurately size components to ensure that they fit inside of the box too.

MoI SW+40 SWL 
The user interface is among the most simplistic and intuitive of any 3D modeling program.

I was now ready to print out the top-view at real-world scale using the layout program CorelDRAW!.
I affixed that to the top of the metal housing and had a template by which I drilled the exact sized holes.

SW+40 QRP Enclosure   As expected and to the millimeter, every part fit perfectly! (Thanks Moi3D!)

SW+40 QRP Controls   I used a "Baby Label Maker"(a common hand-held labeler) to denote each control function.

There 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 control boards.

SW+40 Dial   An accurate analog dial was affixed.

To 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!.
The 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....

Later, 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.

J-38 Key   No station 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)

SW+40 QRP CW Transceiver   Here is 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 & tweaks:
• Upping the power output if possible...  [COMPLETED - See the Miniboots Amplifier below]
 With a few adjustments to the base SW+40, I could only get just a little over three Watts, but with any output above 2.3 Watts
   the signal output acted erratic, or maybe it was frequency instability - None the less, it looks like 2 Watts is the max for this rig.
   There is a power mod presented by KC8AON
   I attempted to try his component value changes but was unsuccessful. The max output voltage was now then limited to 2 Watts. Yes, the signal was stable,
   but not increasable. --- The SW+40 was designed to work optimally at 2-3 watts, if you exceed this, signal distortion will occur.
• An outboard audio amplifier with speaker, which would be great for Elmering opportunities. [Purchased a device to do this - would like to homebrew one]
• An RIT (Receiver Incremental tuning) control.  [only if the rig had a "zero-beat" detection device]
• Touch sensitive paddle circuit for eliminating the need for an additional paddle or key.  [Tried one but ran into RF-feedback issues - will not proceed]
A nice compact sealed lead-acid battery pack would make this rig more portable.  [COMPLETED - will consider a Lithium Ion cell]
• Consideration for using a different method of frequency selection. At the moment I'm using a bank of NP0 capacitors on a rotary selector switch,
   But I may try widening the bandwidth by changing C8 on the SW+40 board and replacing the band selector with a fine-tune potentiometer.
    [Widening the bandwidth would not be good. - perhaps temperature compensations]
• Would like to add a "Zero-Beat" indicator.  This may be implemented within the enclosure of a amplified speaker, but a single RGB LED could be implemented within the SW+40 case.
• Would like to replace the on-off toggle switch with a three-position switch (2P3T) so that the middle setting would set the SW+40 to 'receive only' to inhibit transmit,  The switch would cut the keying line between the Pico-Keyer and the SW+40.

Completed Tweaks:
• 01/28/12 - 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.
I 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 switch.
Consequently, other mods can be made to that type of rotary switch yielding other combinations including a 12 position version!
I 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 thresholds.
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 guaranteed.
• 02/26/12 - Completed trial on using a 1k potentiometer to attenuate the AF output - thus protecting my ears with strong signals.
• 02/28/12 - Completed constructing and running initial tests on a KD1JV Digital Dial / Frequency Counter with 4-digit LED display.
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 features:
   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 tweaked positioning did not take into account the sized of the Radio Shack stand-offs.
     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 also room for the Digital Dial. The jacks and connectors were placed on the sides.
     A clean coat of aqua colored spray paint finishes it off.  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 previous connection.
     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 PK+ chip as other circuits in the rig were also powered up.
     The keyer control MOSFET was left momentarily unstable and 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 on-board 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 (a metal 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 trimmed 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!
My 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 that part of the circuit.  Will I plan to change over to this method, probably not since I have my frequency specs close to accurate with my current configuration.
• 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 we connected it to a very complex looking spectrum analyzer with all kinds of bells and whistles.  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 builders claiming that more power is yours by modifying the circuit.  If 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 'quantity'.
• 03/03/13 - Completed a multi-feature version of the
NB6M "Miniboots" QRP-Gallon amplifier:
   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 circuit, 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!
Since 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.
• 05/13 - Completed several enhancements to the complete QRP setup: Purchased a tool-bad at the surplus store to hold everything in.  I cut a shape from a piece of surplus plastic using as footing in a camouflage netting system to make an antenna wire caddy.  Set up a sealed-lead-acid batter (3.3ah) along with cabling and fuses to run the SW+40 and amplifier.  Other accessories included.
• 01/11/14 - Tweak to the SOTA Tuner.  Replaced the original wing-nuts used for the terminals with multi-type banana-plug terminals.
• 01/20/14 - Replaced 5k ohm 'audio-taper' potentiometer used to control audio output volume with a 1k ohm 'linear-taper' augmented with a 1k ohm fixed resister to create a better custom response to the audio drive of the SW+40.  Tweaked resistor value of Pico-Keyer tone line fed into audio.  I am happy with the audio volume control with an improvement in the SW+40's side-tone feed.  If I can filter the beep tone from the Pico-Keyer, I may consider using it instead and muting the on-board side tone, but this is not a priority.
• 03/01/14 - Added labels to describe functions of each control.

PicoKeyer-Plus    This is a finished PicoKeyer-Plus from

The PicoKeyer-Plus is a very compact device that provides iambic keying "dits" and "dahs" from your side paddle to any radio originally intended to 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".
It 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 .

PicoKeyer-Plus    It's also pocket-sized.

Phase 2   Here is the completed Phase 2.

A 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.

Time to implement PHASE 3 :::

Tayloe Battery Status Indicator Kit    This is the N7VE Tayloe Battery Status Indicator Kit.

Another fine kit from Hendicks QRP Kits at
This circuit Illuminates a Tri-Color LED according to user-determined voltage level thresholds. You can also illuminate separate LEDs if you wish.
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 12+ Volts.
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 Full-Color LED.
This board is tiny, so I actually soldered it to the prototype board along with the PicoKeyer+Plus using expelled component leads as board traces.
Do not fear learning how to use transistors to do your bidding, there are kits, manuals, courses and online information to help you learn.

Tayloe Battery Status Indicator Kit under test    Here is the BSI circuit under test.

I used a potentiometer to "dim" the voltage to the circuit triggering its threshold levels determined by trimming potentiometers on the board.
The 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.

PicoKeyer-Plus on prototype board   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.

MoI3D CAD Component Visualization    MoI 3D put to good use again!

With 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.

Component Placement with MoI 3D    Crucial spatial alignment...

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.

MoI 3D Gets the job done...     I was able to make mistakes and revisions in the "virtual world" first before work was done.

In actuality, there are always unforeseen details, and objects are always smaller on the screen than in real life. I would run into slight problems later.

Drill Template from MoI3D     Drill template.

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".
My 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 Display 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.

Fabrication     Here is the final drill and file work.

Thanks to the template, the drill-work was accurate to the 100th of an inch.

Painted Enclosure     Finished enclosure ready for components.

A test fitting was made with the components and minute adjustments were made.  The enclosure parts were then sanded with fine-grit paper 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.

Internal Wiringqrp_sw40_27_internals-wiring.jpg     The internal wiring.

The 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.
Wire 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 was finalized.

Internal Wiring     A closer view of the component placement.

Most 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.

The "Ice Box" QRP CW Station     Here is the final station setup for the new "Ice Box" QRP CW station!

The "Ice Box" completed     This completes PHASE 3.

The paint job came out nice, and the aqua-colored LED is a nice touch.  Yes, the paint will chip and scratch easy. Only powder-coating 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.

Digital Dial     A close up of the KD1JV Digital Dial.

Here is a close up view of the KD1JV Digital Dial available from Hendricks QRP Kits at
This 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.
The red diffusion lens was found on a discarded digital alarm clock. It was adhesive and peel right off of it's original clock display.
Since 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 plastic film.

Installation notes for connecting the KD1JV Digital Dial to the Small Wonders Lab SW+40:::
The 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.
There 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 cancel 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.
To 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 the 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.
Tune 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 display changes.
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.
Note: Anything below 7,000.00 kHz will give a strange reading. You don't need to go there anyways!
Also, 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.
I also suggest to install the following parts to the opposite side of the board from which they are in the instructions: The mode switch, 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.

PicoKeyer-Plus MOSFET Control Fix

This is a close-up view of the prototype board that houses the PicoKeyer-Plus, the Tayloe BSI, the LED control circuit, and other simple sub-circuits.

The resistor soldered to the bottom is the 1.5 Mega Ohm "pull-down" stabilizer resistor for the gate of the keyer 2N7000 MOSFET.
Normally, 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.
Above, there 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 audio line.
The PK+ provides it's own side tone, but this is disabled through it's programming menu since the SW+40 already provides it.
However, 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.


Miniboots, Dead-Bug Construction  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 by Wayne McFee, no longer in production as a kit.

For more information and a circuit description on the NB6M Miniboots Amplifier - please visit:  

Here is a copy of the Wayne McFee, NB6M "Miniboots" circuit:

The version shown here works best on QRPp transmitters.

Miniboots Circuit

The circuit I used (below) was the resistor network version meant to lower transmitter output of more than at least 3 watts.

Miniboots Circuit

[Once Completed]  This vesion allowed me to set my SW+40 at a very cool 0.7w input yielding an even 5 watts (QRP) from the amp.

Other variations can be found at:

Using the copper-clad board 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 only 0.7 watts, ensuring that the final transistor in the SW+40 would run more efficiently.  The Drive Adjust pot makes for a good wattage-level control but should be adjusted for 1:1 SWR at the transmitter.
I've made a couple of tweaks (not shown above) to better match the Miniboots to my SW+40:  The above circuit uses a step-down transformer to attenuate power, but I used the attenuation network shown in the two-band circuit shown on the NB6M site.  Instead of 150 ohms, on the pad, I used 120 ohms to make a more accurate 50 ohm match. (a good online attn. pad calculator helps).  There is a 33 ohm resistor shown on the drive adjustment for bias and I used a 100 ohm.  These are just little tweaks made to better accommodate my SW+40.
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.  I tried several models using the AADE Filter Designer software and also one or two other ones I found in other schematics, but frankly, I'm not sure how NB6M came up with his values... (I'm not an RF engineer) but with some trial and error I came up with a filter component combination 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 - all things out the window... 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 (with the SW+40 set at 0.7w) maxes out at 5-6 watts at the high-end of the band but tapers down to near nothing at the low end!.  I should be able to lower the inductance on at least the initial toroid to see some improvement.  Nonetheless, I'm at my 5 watt "QRP" target for much of the QRP areas of 40 meters.  I would like to rebuild this circuit (with some variation) with a different enclosure at a later time.

Amplifier Finals   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.

RF Sensing Relay Test   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.

Miniboots - 12 watts!   Proof of the "Miniboots" linear QRP amplifier in action:  0.7 watts in - 12 watts out (at 13.8 volts source).

Miniboots - Enclosure   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.

The Drive Adjust pot (large knob) works for input signal attenuation control and is intended to set the bias, it can essentially choose 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.
The 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.  Also, variations in output signal power due to SWR will show a more varied fluctuation in the red LED luminance.  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 via a 6-amp laptop DC cord.  BNC female RF connectors are on the sides.

My design goal was to place the Miniboots amp within a shorter project box affixed below the SW+40 box, which would have provided space for additional goodies, however, the thick aluminum box made for a very attractive stand-alone unit.  When you add the clunking noise from the relay, the slight mount of heat from the MOSFET and the other bulky parts, in a good way, the entire package has an imposing feel.

Miniboots ugly construction  Click on this pic for a larger view...

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.


Elecraft T1 Automatic Antenna Tuner  Here is shown the kit-building process for my new Elecraft "T1" Automatic Antenna Tuner.

This 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.

Elecraft T1 ATU   Here is the final product.  This thing is tiny indeed - about the size of a pack of cards.

I 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.

K4ICY QRP Station - March 13  Here is my complete portable QRP station (for 40 meters) set up on a table on my back patio.

At 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 right.

QRP Antenna Kit   The QRP Quick-Disconnect Antenna Kit

Making the task of installing the antenna system for the SW+40 a more enjoyable task...

I cut a custom shape out of a spare piece of military-hardened plastic (top left) once used as a foot for camouflage netting system, allowing me to wrap the antenna and counterpoise in quick fashion.
The SOTA Tuner (top right) has been modified with terminals that allow for either banana-plugs, spade-terminals or bare wire.  The banana connectors allow for instant connect and disconnect. The SOTA Tuner is ONLY used when the antenna is connected, through it, to the SW+40.  It will handle a max of 5 watts, and currently, the SW+40 is set for 0.7 watts (QRPp).
A small custom length of BNC coax feedline. (bottom left)  They are not RG-58 (?) and I use three of them.  I do not recommend BNC connectors as they tend to fail, but it is the universal standard for QRP cabling.

A nifty accessory now used by many QRP enthusiasts (bottom right) employs a BNC(female)-to-Banana(female) terminal.  I purchased this one at Fouraker's on Appleyard Dr. in Tallahassee. The banana terminals allow for antenna leads with banana plugs for quick connect/disconnect along with utilization for spade-terminals and bare wire.  I use this terminal in conjunction with my "T1" auto-tuner when running more than a few watts and it is not feasible to use the SOTA Tuner.  These terminal adapters generally come with two holes located in the body which actually allow for an additional pair of banana plugs to come in contact with metal in the adapter, but I used them to pass a length of parachute cord.  I tied the ends after placing a spring-loaded cinch which allows me to attach the antenna's base to a sturdy object, such as a branch or table leg.  These cinches are often found on small bags and back-packs commonly used with backpacking.

Once deployed, if anything happens to the antenna the radio is sure to remain safe on the table!

Labels applied   Here is the "Ice Box" SW+40 with clear labels applied

Label Detail  

I was hesitant to add labeling to my SW+40 for fear of marring its spartan look.  It was always in the plans but I desired something more permanent and professional such as screen printing.  I have the resources at work to have done this, but not with out some trial and error and some risk to the product.
After showing it off at our club's booth where we participated in the National High Magnetics Laboratory's open house, it was clear I needed to expedite the labeling process... well, with the 5000+ visitors that stopped by - giving TARS our best PR exposure ever, I figure I had been asked enough.
I spent a couple of hours Saturday night with my wife's Dymo label maker, some clear label tape and produced the necessary verbiage.
Each label was cut down to close dimensions and affixed under each control... simple.
At least the general ham has more of a chance of recognizing my radio's controls. - I do feel that it has lost some of it's Braun-esc design simplicity.
I believe that eventually,  the labels will turn dingy yellow or brown and peel off, but I can always re-paint it.


There are still issues to resolve...

• There 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 others to remedy this problem. So far, my attempt at filtering has produced no real results.
• Other improvements and fixes involve changing the audio volume potentiometer from a 5k ohms to a 1k ohms or less. [DONE - improvement to volume control, side-tone and PicoKeyer beep tone]
• 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.
More than a few ops I had a QSOs with noted an abrupt frequency shift which is due to the thermal instability of my VCO and the array of capacitors I used, and I also believe a faulty antenna cable has been at fault for abrupt shifts.
• May consider better internal wire management, and also bonding the two case shells.  I may also consider applying a toroid for RF-blocking to the keying, audio and power lines.
• 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.
• A second case can be attached which would hold: 1) isolated class-D audio amp and speaker  2) Lithium-Ion power cells (maybe 4) along with 2-amp boost converter and charging/protection circuit  3)  Replace the Pico-Keyer with my Minty Keyer  4) Arduino-based tuning circuit... this one would use an Arduino to control an IC-based RF switcher for select banks of trim capacitors as well as providing exact voltages to the VCO.

EXCITING NEWS!   [01-15-18]

Rick Choy, N3HXT, at Midway Electronics in Middletown VA has taken on Dave Benson's SW+40 and is now again available for sale, now called the ME40+!   Rick has spiffed up the original manual to have a "Heathkit" style to it and offers the kit in 40, 80 and 30 meter versions with 20 meter version on the way.  Visit or contact Rick at for more details.  You can order the MExx+ on eBay as well as Rick's website.


Other than a few minor remaining issues - I'm very satisfied with the results.
I 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.
Everything 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  [Site and kit no longer available...]
    Please visit Rick Choy, N3HXT's Midway Electronics for the new ME40+
Dale Botkin N0XAS - PicoKeyer-Plus / Iambic Memory Keyer -
Steve Weber KD1JV - Digital Dial / Frequency Counter -
Sumner Eagerman WA1JOS - CW Touch Keyer -

I plan on having lots of fun furthering my learning of CW and making great contacts.

Kit building is a wonderful pastime, and learning basic electronics (even if intellectually) should be a right of passage for all "hams".

73 DE K4ICY SK ••

Go build you own!

Edited: 03/19/20
2020 Copyright - Michael A. Maynard