Subject: So You Want to be a Builder, Huh? Part 3
Date: Mon, 12 Aug 2002 00:44:20 -0700
From: "Doug Hendricks" <firstname.lastname@example.org>
To: "Low Power Amateur Radio Discussion" <qrp-l@Lehigh.EDU>
If you have been following this series, you have been through the Tuna Tin 2, VE3DNL, and the ScQRPion Stinger Singer. Now we are ready for our first commercial kit, the Rock Mite, which is a crystal controlled transceiver that was designed by Dave Benson, K1SWL as a project for the attendees of Lobstercon and Ft. Tuthill. The project turned out so well that Dave decided to make it a commercial product and I am sure glad that he did.
The Rock Mite is on 40 meters, it is a CW Transceiver, and I think it is the easiest to build CW Transceiver in the history of ham radio, grin. The kit is a bargain too, costing $25 delivered to your door if you are in the US or Canada. Please check http://www.smallwonderlabs.com/ for info on ordering the Rock Mite, and for cost if you live overseas.
When I built my Rock Mite I used the following procedure. The first thing that I did was to solder the NE612 IC on. It is in a SOIC package, which means it has 50 mil spacing of the pins. Here is how I did it. I placed the IC on the board, making doubly sure that it was oriented correctly. I checked the layout twice to make sure. When I was positive that I had it the right way, I held it with my finger pressing down, and lined up the pins with the pads. Then, I tacked one pin on the corner. Checked to make sure the rest of the pins were lined up, and they were, so I soldered the opposite corner pin. I checked alignment again. Everything was fine, so I soldered the rest of the pins. Piece of cake. (Yeah, I know, I've done it many times. But you can do it too!! Just take your time and check and recheck). If it is not lined up after the first pin has been soldered, just touch the first pin with the iron and when the solder flows, adjust the IC until it is lined up, and then proceed.
Next I soldered in the two IC sockets, making sure that they were oriented right, and flat on the board. Then I soldered the transistors, then the diodes. Then the two crystals, making sure to ground both of them using clipped off resistor leads. Next, I separated all of the capacitors. I noted that there were several mono caps, the gold ones, and that there were 6 marked 104, and 1 marked 102, but that they all looked similar. To keep from misplacing a cap in the wrong place, I decided to solder in the 102 cap first, then all of the 104's. Next, I put in the 103's, then worked down in value until I had all the caps in. When I put the electrolytics in, I double checked the polarity, making sure that the longer lead went into the hole marked with a +. It became easy to find where they went because of the "landmarks" of the IC's and transistors on the board. I was careful to check the silkscreen and parts placement guide in the instructions. Both are accurate as far as I can tell.
After I did the caps, I found the three chokes and installed them. I had 3 to do, 2 of them being the same value and one being different. Again, I installed the odd one first, then the 2 of the same value. That is very important in this kit, as the 1 is a 10 uH and the two are 1 uH. Easy to confuse and get the wrong value.
I am going to let you in on a secret that I use when sorting resistors. I orient them the same way, (gold band at the same end), and then sort first by the third band. Black, Brown, Red, Orange, Yellow, Green. Then I sort each "band" group by value, high to low. When I finish I have the resistors all in order on the bench top, running from high to low in value. Then I took the board, found where a resistor went on the parts placement guide, then it was a simple task to find that value and solder it in. Another trick. Use the circuit board to act as a lead bender for the resistors. I hold the body of the resistor against the edge of the board and bend the resist over the board 90 degrees. Then, I take the lead and finish the bend making it 180 degrees and making a U shaped bend. The board edge acts as a gauge to keep every thing the same. I also orient all caps so that I can read the value from the bottom of the board, and from the left side. Resistors are mounted with the gold band against the board. If they are mounted flat, the gold band goes to the right or to the bottom, depending on the orientation of the resistor.
When you finish the resistors, you are done. I always install one part, turn the board over, spread the leads so the part holds itself in, and solder. Then the next part, etc. I mount all parts on the board as close as I can, except for crystals which I mount about 1/32" off the board.
When the board is done, you are ready to inspect. Turn the board over and look at every solder joint. They all should be bright and shiny, and there should be a part in every hole, except the ones for the connector wires. I like to use solid wire to make my connections to the connectors. I use #24 insulated solid wire. (A good source is some twisted pair telephone cable).
Now set the board aside as it is time to prepare the case. I made my case out of pc board, but you can use anything that you wish. Drill the holes for all the connectors and make sure that they fit. Then hook up the connectors to the board using the hookup wire. Since I used a metal case, I did not run a ground wire to any of the connectors, but used the common ground of the case. I did ground the board to the case though.
Why is the Rock Mite recommended as a first transceiver kit? Because it is easy to build, it is cheap, the directions are very clear, the board is first quality and easy to solder, the parts are easy to identify, and it is very hard to screw this one up. It is gonna work. Plus, you get to work with several different types of parts now, and because you have some experience and confidence from successfully building the first three kits, this one is a "snap". Believe me you will be proud of it and yourself when you finish.
Let me go back to the board. Dave Benson is among the best in the business at laying out boards. Nothing makes me more irritated than to buy a commercial kit, and find out that the parts don't fit!! I hate it when I have to bend capacitor leads to fit holes. I have never had to bend a lead to make any part fit on a Dave Benson designed kit. That is important to newcomers, because if you have to bend the leads to fit, you got the wrong part in the wrong place. Dave pays attention to small details like that, and it shows in the quality of his kit. His kit is also silk screened and solder masked. Why anyone, anywhere would use a board in a kit that was not silk screened and solder masked is beyond me. The cost is pennies per board, and the problems that it saves are huge.
Another reason for picking the Rock Mite is that there are NO adjustments to make when you finish building. You don't have to peak any circuits, adjust any trimmers, wind any toroids, nothing, nada. It is truly a plug and play radio. Perfect for the beginner. This concludes Part 3. In part 4 we will look at a couple of station accessories that give you even more experience homebrewing, and give you a couple of pieces of gear that you will need to get on the air. See you next time. 72, Doug, KI6DS