Small Wonder Labs Rock-Mite

The Rock-Mite was a neat little CW transceiver kit from Small Wonder Labs. These little kits were available for either 40 or 20 meters. The example in the photograph was built for 40 meters and came with crystals for the popular 7040 kHz QRP frequency. The 20 meter version is on 14060 kHz.

The Rock-Mite 40 uses a very simple direct conversion receiver, however a 7040 kHz crystal is placed in the RF path between the antenna and the SA612 mixer chip. This acts as a crystal band pass filter and greatly reduces interference from short-wave broadcast stations.

The oscillator uses a second 7040 crystal to feed both the receiver mixer and the transmitter chain. A preprogrammed 12C508A microcontroler PIC chip is used for several functions, including crystal offset control. On transmit, the crystal frequency is shifted approximately 700 Hz. The offset is reversible permitting two "channels" of operation, separated by 700 Hz.

Another function of the PIC chip is a built-in iambic keyer, adjustable between 5 and 40 words per minute. If either dot or dash inputs are grounded at power-up, the PIC chip bypasses the keyer function and the opposite input line accepts a straight key.

This rig is unique in that the only control on the transceiver is a single push button. A brief press of the button reverses the crystal frequency offset. A longer press of the button enters the keyer speed adjustment mode where the dot and dash paddle switches will speed or slow the keyer.

While this rig is Altoids compatible, I chose to use a slightly larger Whitman's Sampler candy box. As you can see from the photograph, there is room for an internal 9 volt battery. I called this my Rock Candy Rock-Mite!

The completed transceiver is shirt pocket size and is ideal for backpackers to carry on the trail. The white push button on the front is the only control and this rig can be easily operated in the dark or with gloves.

This tiny transceiver was available as an inexpensive and easy to build kit. It will operate from either a 12 volt supply at 500 milliwatts or from a 9 volt battery at about 200 milliwatts output power. Thousands of Rock-Mites were sold by Small Wonder before Dave Benson retired and closed the business.  However, QRP'ers can still purchase a newer version from QRPme in Maine.

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Updated June 15, 2016