The SMK-1 is tiny! The circuit board measures 2 1/2 by 2 1/4 inches and uses surface mount components to build a working 40 meter CW transceiver.
NorCal did not design the SMK-1 to be a high performance rig. Instead, the underlying purpose of the kit was to train amateur builders in the art of working with surface mount components. Doug Hendricks, KI6DS, observed that normal through-hole electronic parts were becoming difficult to obtain in large quantities. If new advanced kits were to be designed, it was obvious that a transition to surface mount parts would be needed. Since most hams lack experience and confidence building with SMT (Surface Mount Technology) parts, a training project would be desirable. Hence, the NorCal SMK-1 was created as a low cost trainer. Once completed, the project could be used on the air for actual contacts in the 40 meter band.
The SMK-1 is a simple direct conversion receiver combined with a small transmitter. NorCal designer Dave Fifield, AD6A, combined the Columbus QRP Club MRX-40 receiver with the Tuna Tin 2 transmitter and converted them to SMT parts. He further refined the design with improved TR switching and RX muting circuits.
While this is a transceiver, it technically is a separate transmitter and receiver on one board. There are separate crystal VXO's with independent tuning controls for the TX and RX. The receiver covers approximately 7035 to 7039.7 KHz and the transmitter covers 7037.5 to 7039 KHz. There is about a 1.5 KHz window of overlapping coverage where QSO's are possible.
The direct conversion receiver uses a SA612 mixer and a LM386 audio amplifier chip. Selectivity is nonexistent, but the receiver actually hears pretty good for such a simple design. Typical of DC receivers, there is a bit of foreign broadcast AM breakthrough in the evenings to contend with. The modified TT-2 transmitter puts out about 300 milliwatts of RF when powered from a 12 volt battery.
SMK-1 Construction Tips
Building the SMK-1 takes a steady hand and a large magnifier (at least for this builder)! Start by reading the 8 page instruction manual carefully. The tiny parts are presorted and sealed in individual chambers in two parts bags. DO NOT OPEN THE BAGS UNTIL THE PART IS NEEDED!
The photo above shows the PC board with about half of the SMT parts installed. It's a bit hard to see them, but they are there! The little black object in the tweezers is not an insect, it's the PA transistor for the transmitter. The 1206 package SMT parts used in the SMK kit are actually the larger size SMT components. There are even smaller parts manufactured!
Clean off your work table and don't build this kit over a rug floor. Open one bag chamber at a time and solder each part before proceeding to the next bag chamber. Many parts look alike with no markings, so they will be easily mixed up if more than one bag chamber is open. If you drop a part onto a rug, it will be lost forever!
Use a very fine tipped soldering iron and tweezers to install the parts. Once you get the hang of it, this little kit can be built in about 4 hours, but don't rush it. Take your time and practice various techniques for SMT part installation. There are also a few standard through-hole parts, like the two crystals and the three panel controls to install. Yes, there is also one toroid to wind.
On first power up, my kit receiver worked, but the transmitter was dead. Troubleshooting with a digital VOM, I soon found one bad solder connection that prevented the TX crystal oscillator from working. One touch with the iron and I was on the air. Not too bad for my first SMT project!
For More Information
The SMK-1 kit is no longer available from NorCal. The last kit was sold during June, 2001, although SMK's sometimes are offered for sale on the QRP-L reflector. Click on the NorCal link below for more information. The New Jersey QRP Club also offered a SMK-1 enclosure kit to dress up the completed kit.
The SMK-1 was an ideal low-cost trainer to get you over the fear of surface mount.
SMK-1 and Surface Mount Technology Links:
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Updated June 4, 2004