The Rock-Mite QRP HF Transceiver

A tiny, direct conversion
CW transceiver for 80, 40 or 20 meters.


 

LINKS

Small Wonder Labs


 

WHAT IS THE Rock-Mite?

 The 'Rock-Mite' design is a 'one-evening' CW transceiver kit which would be both affordable and easy to construct. I own one for 80m, 40m (7.030 and 7.040), 30m and 20m. The designer is David Benson, Small Wonder Labs and the NorCal QRP club.

     The Rock-Mite is a crystal-controlled direct-conversion transceiver operating on 7040 KHz, the North American 'watering-hole' for QRP activity, or 14060 KHz for the 20M version. The 80M version operates on 3579 or 3686 Khz.  It has an 8-pin PIC microcontroller on-board 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.

SPECIFICATIONS:-

- 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

- Tuning: fix-tuned, two frequencies ~7039/7040 kHz (7121/7122 kHz Novice/Tech+)

 (~14060/14061 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

The Kit and modifications

This is what the kit looks like.

A web search will locate all sorts of modifications for RIT, to add side-tone, increase the oscillator tuning range etc...
If you really want to see what others have done with their Rock-Mite visit N0RC site.

WHAT RESULTS CAN BE ACHIEVED?

People have achieved some remarkable contacts with these little rigs. It is not uncommon to hear of people working many countries on both 40m and 20m.