The Small Wonder Labs “Rock Mite”

The Rock Mite is a complete QRP CW transceiver kit available in 20, 40 or 80m designed by Dave Benson K1SWL. It consists of a crystal control local oscillator for transmit and receive. The design includes a PIC processor programmed to operate as an iambic keyer as well as provides T-R offset. The T-R offset yields a second operating frequency by shifting the CW offset. By tapping the mode switch you switch the CW offset. Holding the mode switch down for one second permits the operator to adjust the keyer speed. The DITs raise the speed and the DAHs reduce the speed.

You will notice in the pictures that there are two crystals. The second crystal is used a filter for the receiver to increase shortwave broadcast rejection. There is an optional preplanned mod on the board to increase AM broadcast rejection (helpful if you live within a few miles of a AM station).

The kit itself is very well packed and organized. The Rock Mite kit consists of the board and all board level components. All the components are sealed in a compartmentalized plastic bag. If you have a well stocked junk box you can add you own connectors. There is a Control/Connector kit that includes all of the jacks, the potentiometer and knob, the power plug and hookup wire.

This is a very easy to build project that can be completed in an evening. Even though there are no toroids to wind (sealed inductors are used throughout) I would not recommend this as a first-timer’s kit. There is a 8 pin SMT IC in the design. Though the spacing of the leads is wide, care and some good soldering skills are required to install this component. Simple tools are required – needle nose pliers, flush cutters, a 15 -25 watt soldering iron and rosin core solder. Solder wick is a good thing to have around if you find that the 807’s interfered with construction. A VOM is handy if you have problems seeing the colors on resistors and I personally used a lighted magnifier.

Actual construction is quite simple; all you do is stuff the parts into place. You aren’t held by the hand ala the old Heath Kit manuals. You are given suggestions as to which components are best installed first to ease subsequent parts placement. I followed the suggestions and then placed the parts by type: resistors, caps, diodes, etc. The parts list has a convenient check box column so you can check off the parts as you place them.

The smoke test was rather confusing for me. I had my 817 set on 14.060 and as soon as I put power to the Rock Mite I was treated to a howling sound on the 817. I had thought that I had the transmitter keyed up somehow. After I re-read the manual (pays to read the manual and the supplement) I realized that I was hearing the local oscillator. Power output from my particular unit was 700mW per my QRP watt meter.

My first verified QSO was with Pete K9OFU in Wisconsin. My reported RST was 237. The whole QSO was quite accidental. I was sitting out on my back deck with the Rock Mite hooked up to an end fed ˝ wave antenna. I heard a surprising number of signals. When things quieted down I called CQ, mostly to get a feel for the keyer. Damned if someone didn’t answer me! I was now stuck between a Rock Mite and a hard place. I was stuck copying in my head as I did not have a pen or paper. I survived. Thankfully Pete didn’t mind plodding along at 10 wpm.

No enclosure is available from SWL but the board fits nicely into an Altoids case. These are not only easy to come by; your finished radio will smell nice! I opted for the “MityBox” ($20) from Americanmorse.com. The “MityBox” is a beautifully CNC machined box and comes with all the necessary hardware to install the Rock Mite.

Conclusions: All in all the Rock Mite is an easy to build, fun to operate kit. I would recommend this kit for someone with some kit building under their belt or for a newbie with an Elmer.

The Rock Mite is available from Small Wonder Labs (www.smallwonderlabs.com) Parts & Board $27.00 Connector/Controls $12.50 Prices include shipping

The MityBox enclosure is available from American Morse Equipment (www.americanmorse.com)

SPECIFICATIONS:-

• - Double-sided PCB 2.0" x 2.5", plated-thru-holes, solder masked & silk-screened for easy assembly
• - 0.5W power output at 12V supply.
• - Supply voltage range 8-15V
• - Tuning: fix-tuned, two frequencies
         ~7039/7040 kHz (7121/7122 kHz Novice/Tech+)
         ~14060/14061kHz on 20m
         ~3579/3580 KHz (3686/3687 kHz Novice/Tech+)
• -automatic T/R offset, reversible
• -Built-in Iambic keyer, 5-40 WPM
• -Built in sidetone, 700 Hz
• - Includes assembly instructions and operating tips
• - All on-board parts supplied in kit (as pictured above)