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Building the SW-80/40/30/20
QRP CW Transceivers
from
Small Wonder Labs

 

In February and March 2011 I built two QRP CW rigs from Small Wonder Labs -- the SW-80 (80 meters) and SW-20 (20 meters). 

Small Wonder Labs is a mom-and-pop operation in New Hampshire by Dave Benson and his wife.  Dave produces top-quality QRP rigs and accessories.  The SW (Small Wonder) QRP CW transceivers cover the main HF bands -- 80, 40, 30, and 20 meters. 

In early 2010 I built a SW-40 and put it on the air.  In March 2011 I built the SW-80 and SW-20.  The rigs are similar, the only difference being their frequency coverage.  In this article I will describe some of my experience in building these three rigs.

General comments

Dave Benson at Small Wonder Labs produces excellent products.  I have built:

  •   Three of his Rockmite transceivers (1/2 watt output; crystal controlled; 80, 40, and 20 meters; mount in Altoids box);
  •  Three Small Wonder transceivers -- SW-80, -40, and -20;
  •  Several FreqMite frequency counters.

All of the Small Wonder Labs kits are carefully designed and tested and use top quality components.   Dave responds quickly to email requests for assistance and is very helpful.

The instructions that accompany each kit are quite good.  While not exactly step-by-step, I believe even a first-time kit builder would have no problem with any of Dave's kits.

Building the SW- series QRP transceivers

The following is my experience in building one each SW-80, -40, and -20.  I've included some photos.  In no way does the following take away from the instructions that accompany the SW Lab kits -- read those instructions carefully.

Tools to assemble a SW Lab kit

Here's a photo of my workspace.  If it looks like a roll-top desk, it is.  I do not have a spacious ham shack and workshop.  When I build a kit, I turn my roll-top desk into an electronics assembly center.

Here's a SW- rig ready for assembly.  My tools consist of:  Weller variable temperature solder station; small needle-nosed pliers; small diagonal wire cutters; wire stripper for wire as small as 24 gauge; solder; small precision screwdrivers; digital multimeter; OptiVision magnifier (2X with 4X loupe); large tweezers.  On the other side of the roll of solder is a roll of ribbon wire that I use for interconnections inside the enclosure.  The muffin tins are used to hold small parts.


This is what you see when you open the package containing the SW- kit.

That's it.  That's the entire transceiver in one small plastic bag, minus the tuning and audio gain controls, antenna connector, power connector, and jacks for key and headphones.  Here are the contents of the package laid out.

Top left corner is the PC board; to the right is a static-free envelope containing the transistors and IC's; a package containing wire to wind toroids, and, three RF chokes.  Bottom right corner is an envelope containing resistors and capacitors; center bottom is a package of IF transformers, toroids, diodes, and IC sockets; bottom left corner is another package of capacitors.

I sort out the CAPACITORS by value and place capacitors of the same value in muffin tins, shown here.

On a small slip of paper I write the value of each capacitor -- e.g., 100 is 100 pF; .01 is .01 mFd.  The markings on the capacitors are tiny, requiring a magnifying glass to read and by sorting and labeling them like this, I can find the one I need instantly.

I do not put the RESISTORS in muffin trays.  Instead, I sort resistors by the first two color bands and simply pile them up on the work surface.  For example:

  •  The rig uses 10 ohm, 1,000 ohm, 10,000 ohm, 100,000 ohm, and 1,000,000 ohm resistors.  The first two color bands for each of these resistors are brown and black.  A 10-ohm resistor is brown-black-black.  A 1,000,000-ohm resistor is brown-black-green.

  •  The rig uses 2,200, and 22,000 ohm resistors.  The first two bands of these are red and red.  A 2,200-om resistor is red-red-red, while a 22,000-ohm resistor is red-red-orange. 

  •  By keeping the resistors separated by the first two color bands, I can find the one I need quickly.  If you want to use a muffin pan to hold your resistors, fine -- I don't because I don't have the space on my desktop.

Diodes

This is important.  If you do this wrong, the rig will not work and you'll tear out your hair trying to find the problem.

Here's a photo of all the diodes used in the rig.

Diodes have a positive end and a negative end -- anode and cathode.  Diodes must be installed correctly or the rig won't work.  Look at the photo carefully and note that each diode has a BAND around one end.  The band shows claerly on most of the diodes in the photo but does not show on the black diode on the right.  Don't worry -- on the real diodes, you cannot miss the band.  Look at this photo of one diode.

This diode is ready to install.  Diodes are installed standing on end WITH THE BANDED END IN THE AIR, NOT AGAINST THE PC BOARD.  Before installing a diode, bend it as shown here with the lead on the banded end bent down.

Now, check out this photo.

This photo shows one diode installed.  Look at the right edge of the PC board where the diode is installed.  Note the label "D7 - D10."  At this point, four diodes are installed, D7, D8, D9, and D10.  Look closely at the board.  Note the label that reads "C113" -- to the right of that label are two tiny circles.  Note that to the left of the label that reads "D7" are two more tiny circles.  D7 dn D8 are installed with the diode bodies next to the edge of the PC board while D9 and D10 are installed with their bodies away from the PC board edge.

In the photo is a large circle labeled C112.  To the right of C112 is a set of holes labeled D6 -- one hole has a tiny circle around it, the other hole is only a solder pad.  D6, for example, will be installed with the diode body in the tiny circle, the banded end up in the air, and the lead from the banded end coming down into the solder hole.

When installing a diode, FIRST bend the lead at the BANDED END as shown in the photo above.  Then, install the diode with its body in the tiny circle and the lead coming from the banded end in the other hole indicated for that diode.  Study the photo above -- this is diode D7 installed and ready to be soldered.  Note that the banded end is up in the air while the body of the diode is in the solder hole with the small circle.


Now, go to page two for the rest of the story.

 

 

Member, North American QRP CW Club
NAQCC #3938

Member
American Radio Relay League

Member
QRP Amateur Radio Club International
QRPARCI # 14145

     

Member, Straight-Key Century Club
SKCC #7954

 

Member, FISTS
The International Morse Preservation Society
FISTS #15405

 

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