Paper, Scissors, RockMite – the Small Wonder Labs QRP Kit Radio 26 - October - 2007Posted by k9zw in K9ZW Built, K9ZW Recommends.
The ‘Rock-Mite’ was designed by Dave Benson K1SWL, and as he puts the reasons so well, from his website:
The ‘Rock-Mite’ grew out of my desire to offer a ‘one-evening’ CW transceiver kit which would be both affordable and easy to construct. It first appeared at ‘Lobstercon’ – a QRP gathering on the Maine coast- in early July, 2002, where it was provided to all attendees courtesy of Small Wonder Labs and the NorCal QRP club.
The Rock-Mite is a crystal-controlled direct-conversion transceiver available for 80M, 40M, 30M or 20M. It features an on-board 8-pin PIC microcontroller which controls a T-R offset on key-down. A brief tap of a pushbutton control switch reverses the offset to yield a second operating frequency. Pushing and holding on the pushbutton activates the speed adjustment routine for the built-in Iambic keyer. If you’d rather use an external keyer or straight key, there’s a ‘drop-through’ mode which allows use of an external keying source.
You’ll note in the image above that the Rock-Mite uses two crystals. The first is used in the local oscillator for transmitter and receiver. The second is used as a receiver front-end filter. This crystal significantly reduces the SWBC energy present at the receiver mixer; as a result, unwanted SWBC reception is dramatically reduced.
The Rock-mite uses one surface-mount part with fairly large spacing. There are no toroids to wind, so assembly should be a snap! The Rock-Mite uses subminiature epoxy-encapsulated RF chokes instead of toroids
Double-sided PCB 2.0″ x 2.5″, plated-thru-holes, solder masked & silkscreened for easy assembly
0.5W power output at 12V supply.
Supply voltage range 8-15V
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
3560 kHz, 3579 kHz, 7030 kHz (DX QRP calling frequency), 7040 kHz (N. America QRP calling frequency), 7122 kHz (US Novice/Tech+), 10106 kHz or 14060 kHz
This kit is a blast to build. Though I took more than one evening to build mine, mostly due not being organized for the build. I put mine in a Mity Box by American Morse and the results are awesome! This is one fun build!
I am afraid I lost my in-process build pictures when the Macbook’s aftermarket large hard drive stopped driving, but the RockMite is well documented on the web.