SWL ROCKMITE CW TransceiverBuilt by WY3A
I heard that Dave Benson's ROCKMITE (Small Wonders Lab) QRPp (400 mw) minimalist transceiver was a good little radio. But I didn't know how good it was until I had mine on the air for a day or two and enjoyed many easy contacts including a DX ragchew on 40 meters. After noticing the RockMite on a local club's website, I surfed around to learn more. I had an earlier foray into QRPp when I built a Pixie II in an Altoids tin for 80 Meters some years back. It was a disappointment. N5VWN, who built the ROCKMITE noted in his e-ham review that though disappointed by the PIXIE II -- the ROCKMITE was a very different story.
Impressed with the reviews, the internal keyer, and the price ($27) I ordered the RM-40 online and waited for my kit to arrive. The same week, I bought a used Circline industrial magnifying light that I found on Ebay. My vision is not what it once was. If I was gong to enjoy building the kit, I'd need to be able see well enough to do it right. The magnifying light and the back-ordered ROCKMITE arrived at about the same time.
Building the radio was a joy with that magnifying lamp and my old Radio Shack "helping hands alligator clip "vice". The first step was to install the lone Surface Mount IC. Uh-oh, solder bridges across a few of the pins -- but after I wicked up the excess solder, it looked good. I mistakenly inserted D6 (odd looking diode that looks like a transistor with just 2-leads) in the wrong place. The silk screened "D6" was close to the holes for R11. The solder had just hardened when I realized the stupid mistake. I was glad to own a soldering iron with two screw-in heaters...one at 23.5 watts and the other at 48 watts. The higher heat was nice when doing certain jobs (like wicking solder off a pad to get all the solder out of the hole or when cleaning up junk box connectors). I took my time building over a few weeknight evenings.
Soon the board was done and it was time to do a smoke test. I put an inch long piece of solder into the hole on the antenna pad, the audio pad and the V+ pad. Grabbing a handful of test leads, I connected my headphones and a cheap 12V supply. No smoke and I hear static. But there is 60Hz hum on the audio. I removed the old (poorly regulated) 12V supply, yanked a 9v battery from the basement smoke detector, hooked it up, and the hum disappeared.
I grabbed a piece of coax to extend my antenna over to the workbench and attached a clip lead to the coax center pin. Signals! I hear lots of CW. There is still some barely detectable hum. I grabbed another clip-lead and ran it from ground to the shield of the coax. No more noise at all. Wow, this little receiver is HOT...THIS ROCK-MITE MIGHT-ROCK! If I didn't know better, I'd think I was listening to stations on my primary radio (with the narrow filters out).
Getting the radio into the Altoids tin was the hardest part for me. It took another evening and morning, including a run to the hardware store for some 4-40 nuts and bolts and a T-handle reamer. During that time I also added a reverse polarity protection diode from the junk box (Dave Benson's recommendation) to V+ . My thanks to N0RC for the Altoids Tin Fabrication Tips. The most important tool for the job was the T-handle reamer. I marked all the holes with a pencil, drilled a small hole (1/8"<) with a new drill bit. I just let the bit spin and hardly pushed at all on the thin metal. Then I reamed carefully to make holes the correct size for each connector.
The junk box supplied most of the connectors. I put a piece of thin clear insulating acrylic from the junk box on the floor of the tin, since my junk box connectors and poor planning didn't allow room for stand-offs to raise the board off the floor of the chassis. I decided to use the small piece of coax supplied with the kit -- untrimmed -- for the antenna connection. With 2 1/2" leads everywhere, I can remove the mounting bolts and flip the board up for modifications or repair.A multimeter in continuity mode helped me ascertain which connector pins map to tip, ring, and sleeve on the jacks. Be sure to plug the jacks all the way in.
ROCKIN' WITH THE ROCKMITE
Once I got the board inside the enclosure, I hooked the rig up to a regulated supply at my main operating position, tested transmit, frequency shift, and keyer functions, which were good, then called CQ a few times. Moments later I was in QSO (contact) with a guy on a fishing trip in the Allegheny mountains of western PA running a battery powered 5 watt rig. He told me he was going to put another trout on the pan for me...but I didn't believe him. That first day, a half dozen easy QSO's were enjoyed with stations from Massachusetts to Michigan, using my low G5RV multiband antenna and a higher 40M 1/2 wave sloping (nearly) vertical dipole. Most contacts were responses to my CQ. The next night I was doing computer work and not paying much attention to the ROCKMITE's audio coming through the headphones which sat on the desk. Suddenly, I thought I heard a very loud F3NB ragchewing on my frequency (7040.9)! The headphones were quickly off the desk and on my head. When their QSO ended, I called, but F3NB worked someone else. When they were done I called again -- F3NB de WY3A WY3A WY3A QRPp K. I was astonished that Andy came back and gave me a 559 report through the QRN on his side. We then enjoyed a 100% solid copy ragchew. He was using a Hy-Tower vertical and I was on my 40 meter sloping dipole at 60 feet.
This was not a quiet morning on 15 meters at the height of the sunspot cycle. This was 40 meters on a summer night with QRN interference on both sides. I kept looking at the Altoids tin in disbelief that I was actually hearing and talking to Andy in Toulouse France through THAT little radio. I even glanced at my big radio to make sure it was turned OFF.
Before the RockMite I had worked many hundreds of European stations on 40 CW -- but never with less than a half watt and a transceiver in an Altoids tin. And -- it might be my imagination -- but I could swear to you that the little ROCKMITE sounds better in my headphones than my full size rig.
Update September 2005: I replaced the the small piece of coax with two short wires to the coax connector. Repeatedly removing the RockMite board from the chassis caused the soft coax center wire to flex, weaken and break. Its a more tidy installation now without the coax piece. To remove the board from the chassis now requires a little unsoldering at the coax connector.
Update January 2009: I've now logged over 100 QSO's using my Rockmite 40, with very occasional use. At least 6 QSO's in the log are DX contacts including Europe, the Caribbean, and South America. I just changed the crystals from 7.040 to 7.030 due to the volume of RTTY and PSK31 activity now on 7040. The replacement crystals were $6 postpaid from Small Wonders Lab. It was simple to remove the old crystals and solder in the new ones in. I'm still having fun with my Rockmite 40!
Bill Patton, WY3AWest Chester, PA