rock mite

All posts tagged rock mite

It’s alive! After three hair-pulling days, the radio finally works. I received the box on Thursday night; no time then to start, but I got to it after my daily work session on Friday. Late that night, I had completed the filter board, one of the three circuit boards.

I must here explain what an Elecraft K1 is.. Though it sounds like some fighter plane name, it is a receiver/transmitter (a “transceiver”) which transmits, and receives CW (Continuous Wave) Aka “Morse Code.” It is very small, and covers up to four Ham radio bands. Mine has two, 40 (7Mhz) and 20 meter (14Mhz). The power output is fairly low (7 Watts), but that is sufficient to bounce your signal around the earth.. Imagine seeing a 7 Watts light bulb thousands of miles away! Somehow, it works. CW punches through further than “phone” (voice). The K1 is in a class of radios called “QRP,” meaning low power, usually 5 to 10 Watts. It is only sold as a kit, so if you want one, you must build it, or find a used one.. I chose to build it..

Elecraft K1

Elecraft K1

I don’t understand the fear about winding toroids. I find it very easy and relaxing; it hurts much less than it sounds. All you have to do is count how many times you thread a wire through a ferrite core. How easier can it be? Then, you burn the enamel off the leads with a lighter, clean them up with your snipping tool, and solder.. I was very exited that night about the project. I thought it would be a walk in the park.. Not quite..

The front panel was next. The only difficulty there was soldering the LCD display. Attaching the wires to the ten-turn potentiometer also required some dexterity. About wires.. There are very few in the K1 kit: The potentiometer lead wires, speaker wire, and one coax jumper on the back of the board, that’s it. Everything else is connectors. I like that. Soldering wires is always a pain in the butt.

The RF board was the biggest and longest one to build. It took me from around 10-am on Saturday to about 2:30-am on Sunday to complete it! And it didn’t work! In retrospect, I should have only completed the receiver part that day, leaving the transmitter for Sunday. When tired, your brain plays tricks on you, and you make mistakes. Everything went fine with the receiver. I heard static when I turned the K1 on, no smoke. After tuning the receiver and plugging-in a long wire, I was listening to CW on both bands. I was exhausted, but proceeded with the transmitter side. It was 9-pm already, eleven hours of looking at tiny components, placing and soldering them.. Then came the time to test voltages on the RF board. Nothing on U8! Shit! Excuse my French.. That wasn’t good. I nevertheless plugged-in the filter board to test power output. Nothing.. Followed about an hour of tinkering, swearing, manual-reading, head scratching shenanigans, of which I remember almost nothing (I had been working on it for 15 hours straight). I rewound the bi-filar transformer, reheated solder pads both on the filter and RF boards, zilch! Then I gave up, and decided to complete the build for the heck of it, and call Elecraft in the morning. Yet, after putting the speaker in and closing the box, I tried again. Power on 40m! Not on 20.. Ah.. Back to it (2-am).. I think I transmitted without a dummy load and no antenna a couple times by the way, I was so tired. Anyway, I have no idea what did it, but after countless little troubleshooting steps, and more tuning of the filter board, I finally got output power on both bands. I packed it up and went to bed with a headache and slight twitching..

Elecraft K1 inside

Elecraft K1 inside

Comes Sunday morning, I had a working K1! The only peculiar thing left to investigate is some power fluctuation.. If I set the maximum output to 2 Watts, the watt meter shows 2W at first, but then slowly climbs to 2.8. I am guessing that the final transistor produces more gain as it warms up.. I even produced about 10W tuning the filter board before the output suddenly dropped! Weird.. After tuning the filter board on receive, things are a bit more stable, still with quite a power increase as transmit time increases.. It shouldn’t occur producing CW though, as this was transmitting a continuous tone in tuning mode. We’ll see..

I spent Sunday evening listening to CW outside, with a wire strung horizontally (20ft maybe) about five feet from the ground; the worst possible antenna. Still, it was easy to pick-up signals. I even heard a guy saying he was on a sailboat, and retired three years ago (I have a Morse decoder app on my iPod!).

The Elecraft K1 kit is of very high quality; much better than any other kit I have seen so far (five). Everything fits perfectly, nothing was missing. I even had much needed left-over screws (I spilled them all on the garage floor).. The box looks great, and the way the circuit boards are positioned and fastened is brilliant. I will order the automatic antenna tuner and add it in soon. For now though, I need to finish learning code, then I’ll go for the General Ham license (CW is no longer required). The K1 was the right choice, at the right price. You get a lot for your money. It might not seem so when you buy the kit, but after building it, I find it very affordable.

To anyone contemplating building one, go for it! Build a couple kits first, like a Small-Wonder-Labs Rock-Mite, and a SOTA tuner from qrpkits.com, and you’ll be well on your way. Moreover, you can test the Elecraft receiver with the Rock-Mite! Get 50ft. of wire from Home Depot for the SOTA tuner, and you’ll be all set. Follow the manual EXACTLY. Don’t skip ahead, read every line! Double-check everything. Most importantly, don’t do what I did. That was stupid. Take your time. If you feel tired or stressed, stop, rest, and don’t get back to it until much later. I was very lucky that I didn’t fry anything. Not to mention the stress and lack of sleep.. Not a healthy way to spend a week-end..

In the mean time, like they say over there, “Everything is fine in the best of worlds.” I am a happy, proud builder and owner of an Elecraft K1. The satisfaction of building something that complex with your own hands is priceless..

After my semi-success with the DC20B, I decided to tackle the Rock-Mite from Small Wonder Labs. I also got the Mighty Box. The kit is very small and has no toroids to wind. It does however have a surface-mounted integrated circuit. Winding toroids is actually very easy. I don’t know why people make such a big deal of it. Maybe they just haven’t tried. Soldering the SMT circuit, while not that hard, was stressful. That being out of the way, the rest of the kit was a breeze. Being fairly confident of my abilities, I installed the circuit board in the box without trying it first. This way, I could use all the connectors for testing. To my satisfaction, it worked the first time!

My goal with this Rock-Mite is two folds. First, it is a stepping stone to building an Elecraft K1, which I have just started, and second, it provides me with a small emergency radio for my bug-out bag.

I can’t really compare the DC20B to the RockMite as far as performance is concerned, but building the Rock-Mite is easier, and there is no tuning required. The circuit board is slightly smaller. I replaced q6 with a 2sc799. R18=2.2 ohms for a little more power. The keyer is the Pico Keyer from http://www.hamgadgets.com.

I am very exited about building the K1. More on that later…

How big of a radio, and for how much money can you communicate across thousands of miles? What about something that fits inside a box of Altoids mints for $29? The best part is, nobody can ever cut you off!

Rock-Mite

Rock-Mite PCB


This is the “Rock-Mite” from Small Wonder Labs.
(Google “rock mite” for Altoids-mounted boards!)

Sure, you’ll have to learn morse code… I can’t think of anything that small however that truly can be used as a pocket emergency radio. Add a long wire antenna, a mini tuner, AA batteries, and you are in business. With the “Mity Box,” and connectors, your total cost comes to $70, still a bargain. My RockMite is on it’s way (20m version)!

Another kit I just completed is the DC20B.

DXxxB

DXxxB PCB

You can see that it is a bit more complex than the RockMite. You need to wind transformers by wrapping a certain number of turns across small toroids with very thin wire. The kit also requires tuning. The Rockmite is pre-tuned. Performance is supposed to be better, we will see…

Assembly took a whole afternoon and evening. I had never soldered on a double-sided circuit board, but it turned out to be fairly easy. I just made sure I had a good solder joint on both sides. I started with the smallest components, resistors and diodes, then integrated circuit sockets, capacitors, and transistors, leaving out the final transistor until everything was squared away. To my delight, I heard morse code when I turned it on and attached a long wire! The volume was very faint, hopefully that will change with a tuned dipole up in the air.

There is one little problem remaining. I have also built the frequency counter kit from N3ZI. The oscillator frequency of the DC20B is supposed to be 14,060khz. I get 14,063.2 minimum.

DC20B Frequency off

DC20B Frequency off

Hopefully I will be able to fix the problem. It might be a calibration issue with the frequency counter. Since I do not have an HF Ham radio, I can’t check it. Once I build the RockMite I will have a way to verify the frequency.

 
[warning]DCxxB builders: C36 has a missing trace to ground. Make sure you solder a short piece of wire from the pad closest to the board edge to the ground..[/warning]

Both the DCxxB and Rock-Mite have keyer chips included. That means it can generate Morse code from an Iambic paddle you plug-in. These radios serve the same purpose. For some, there is the challenge of contacting distant stations on very little power (500mw to 1w). Others take them camping, hiking, and on all kinds of adventures. I am of the second type. The RockMite will have it’s place in my bug-out bag as well. Heck, I might build a second one as a backup.

My choice between the two? Rock-Mite; because it requires no tuning and has no toroids to wind. You can easily find help online, along with a list of possible modifications. Both kits have a Yahoo group. The Rock-Mite group though did not at first accept me! Why? Because I don’t yet have a license and call-sign! The DCxxB group had no problem with me joining. It turns out that the groups are owned by the same person.. And I was accepted at last, after complaining. These kits are a great way to get started, and while groups need to be monitored, access shouldn’t be restricted…

Learning Morse Code turns out to be pretty hard for me. Some people have no trouble and wrap it up in a couple weeks. I’ll be lucky to take only three months! My brain isn’t wired that way I guess.. I use an iPod app: AA9PW Ham Morse. It uses the Koch Method, which is supposed to be better. I had to slow down the learning speed from 15wpm to 12wpm, just to be able to write fast enough. I might just try to build the sentences in my head… I don’t think anyone can write that fast; not me anyway.

As to my HAM license(s), I am in no hurry. I read the Technician class book once and never miss more than one questions on the QRZ.com practice exams. So, I took three General class practice exams, just out of curiosity, passed two! Barely, but still… I am reviewing for that class now. I might as well pass both tests at the same time. Maybe I should get the Extra class as well, why not? If not just to see the face of the examiners, asked which license I am testing for, I’ll say “All of them!” and get close to 100%. Listening to HAM conversations, I have to say that what I have heard isn’t that interesting. It is a somewhat weird crowd. Mostly old fat guys (no offense intended). As to public service, in times of relative safety, radios are useless. You don’t need a ham radio to help with a local fund-raising marathon.. Just use cell phones! I laughed when I heard a “Net,” the controller asking “Is there any emergency traffic?” Are you kidding? We call 911 for emergencies! There is also the “contesters,” who won’t give you the time of day and just want a call-sign and “grid number” to add to their collection. How useless is that? Anyway, there are also great things in Ham radio. Groups do take their transceivers atop mountains and in all kinds of remote areas. I like the idea of it being a safety net, some kind of support apparatus. Besides, you don’t stay in shape by sitting in front of a radio all day…

I will post an article on building the RockMite, with a video, when I get the kit (I was told ten days before it ships).

Here is what comes to my mind when talking about any item: “If it can’t carry you, and you can’t carry it, don’t bother.” These two small transceivers certainly get my thumbs up!

Update (May 27th): I think I am going to ditch the DC20B. I have a box for it, and should complete the build, but after that, it’s going away. I can’t get it on frequency, and I am not the only one… The Rock-Mite kit should arrive this week. I can’t wait to build it. Look for the article!

Update (May 30th): Well, I gave it one last try.. Changed C36 to a 100pF, and C29 to 47pF. It worked! Now I get 14,059.72 on transmit. Receive goes from 14,060.16 to 14,060.32, a perfect 600Hz offset. The problem is the receiver, which has no selectivity. I receive Chinese, French and Spanish commercial radio stations, but little, faint CW signals. Maybe the problem comes from the wire I use as an antenna, which isn’t tuned. I will try a tuned dipole during the day and see if I can get clear CW (morse code). I boxed up the DC20B in a nice Hammond cast aluminum box. I made a hole in the cover to tune CT1 and glued a piece of coax outer insulation so that I can’t touch anything with my screwdriver upon insertion.. The box is a little big, but it looks good and as though it would survive being run over by a semi-truck.. I might make another hole for access to CT2 and add an RCA plug for a frequency counter (for tuning).

Update (August 1st): The tuned antenna did the trick. Good selectivity now, and the radio is on frequency. The DC20B gets the thumbs up!

DC20B Boxed

DC20B Boxed

Note the piece of insulation glued on top of CT1.
I wish that damn iPod could focus up-close.
Still waiting for the Rock-Mite.
I am starting to think about an Elecraft K1.