Friday, September 20, 2013

Small Wonders Labs - Rockmite-40 Build

Since I posted about my Radi0Kit-140 build-out yesterday, I figured that I would post pictures of my Rockmite-40 build today.   For those not familiar with the RM-40, it is another QRPp CW only radio.  It is crystal controller (in this case, the crystal is for 7.030MHz) hence the name RockMite.  Again, being a QRPp radio means that it puts out less than one watt.  In the case of this radio, about 750mW.

Unlike the Pixie, this transceiver has a sidetone so that you can hear your code as you send it, as well as an adjustable transmit offset.  I decided to go ahead and get the connectors/controls option, PicoKeyer upgrade by Ham Gadgets, and a MityBox by American Morse Equipment at the same time that I ordered the kit.

About the transceiver kit from SWL's website:

"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."

About the PicoKeyer from their website:

"Here are the main features of the PicoKeyer-RM:
  • Low current operation - typical sleep current well under .1µA, only 1-2mA when keying.
  • Direct replacement for your Rock-Mite's or Hi-Mite's original keyer chip, no modification to your Rock/HiMite is needed.
  • Simple one-button "menu" interface
  • Setup and message entry using your paddle
  • Speed adjustable from 5 to 45WPM from the paddle - or add an optional speed control pot!
  • Variable pitch audio sidetone
  • Adjustable weight
  • Selectable Iambic Mode A, Mode B, Ultimatic, semi-automatic "bug" or straight key operation
  • Automatic straight key detection. Both message memories are available for playback even with a straight key! (You will need a paddle to record messages, though.)
  • Beacon mode! No switch or jumper required for beacon mode, just insert a special prosign character into your message. Great for calling CQ!
  • Message pause with auto-resume - You can insert a pause to manually send RST or other information in the middle of a saved message.
  • Auto-incrementing, resettable QSO/serial number can be inserted into your messages for contests. Send them with or without cut numbers (0 and 9 only) and leading zeros!
  • Greatly improved tuneup mode for hands-free steady carrier or 50% duty cycle pulsing.
  • Two message memories hold up to 100 characters each. Message memories can be chained to make one 199-character memory.
  • Paddle switching - effortlessly select left or right handed operation without switching wires or turning the key upside down.
  • All settings and message memory is maintained in non-volatile memory, even with power off.
  • "Factory Reset" option to restore all default settings to your PicoKeyer-RM.

The PicoKeyer-RM uses FLASH and EEPROM memory to store all settings and message memory, meaning NO backup batteries and NO lost settings."

And finally, about the Mity Box, from their website:

"Custom CAD/CAM engineered CNC hogout enclosure for the Small Wonder Labs Rock Mite transceivers
  • CNC machined from Aircraft Aluminum billet
  • Designed specifically around the Rock Mite boards
  • Absolute minumum size & weight - 2.2x3.3x.875 inch, under 2 ounces
  • Beautiful Blue Anodized finish - very durable
  • Uses standard miniature off-board components
  • Pre-drilled for all components - board & cover hardware included"

And now, for the build-out:

This first thing that I added was the one surface mount IC.  I keep reading about how easy it was, but it was a serious pain in the butt for me.  To the extent that I had to touch it up after completion of the kit due to a bad solder joint.  But I finally got it!

Adding the IC and some capacitors

Adding the resistors

Adding the sockets for the non-surface mount ICs.

Adding the diodes

Adding more diodes since I forgot some...

Adding the RF chokes

Adding the transistors and some more capacitors

Adding even more capacitors

Adding the crystals

And finally, after adding the ground connections for the crystals, Finished!

Unlike the last post I was so excited that I didn't get any video of the initial smoke testing and subsequent irritation as I tracked down the bad solder joint on the surface mount IC.  I have only minimal test equipment, by which I mean I have one off-brand multi-meter and an off-brand capacitor tester.  But the build documentation is absolutely stellar with this kit, TO INCLUDE a really great troubleshooting section.  It walked me through the testing and verification step-by-step until I had a working radio!

Another great resource is the builder community for the RockMites and Minimilist QRP Radios in Yahoo Groups.  I can't say enough good things about the guys and gals on that email reflector.  Great bunch of folks that are always willing to lend a hand with building tips and troubleshooting ideas.

All-in-all this is an amazing radio, especially for the price!  With the connectors/controls, upgraded keyer chip, and enclosure, I am in for about $77 not including shipping.  For that price you get a radio with tons of upgrade potential, a top notch case, and more fun than you can shake a stick at!  Build-out can be completed in an evening (although it took me about three).  The soldering is a little more challenging than the Pixie, but very doable with a little patience.

The receive on this radio is really good, way better than the Pixie in my last post.  It is much less sensitive to BCI overloading, though not immune, due to the crystal acting as a filter on the front-end.  The only downside that I could find was that it is sensitive to microphonics.  If you tap the case you can hear that tapping in your headphones.

The Mity Box case makes for a really nice and sturdy package for the radio, but be forewarned, it is TIGHT in there.  Plan ahead as much as possible when you are ready for final assembly.

To close out this lengthy post, I really do recommend that you get this kit if you are looking for a fun project.


Richard, KK4JDO

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