I spent the best part of the afternoon looking at the Rock-Mite 40 QRP transceiver today.
I’d been trying to get it working a few months ago before I changed jobs, I had to put the project had to go on hold to concentrate on learning PL\SQL and SQL for my new job.
The last time I looked at it, I knew I had put Q5 in the wrong way around, and I had smoke coming from Q6 when I bench tested the device. So this afternoon I started by removing Q5 and Q6 and replacing them with fresh components (obviously putting Q5 in the right way around). A new bench test produced no smoke, but the transceiver still wasn’t working. A new test of U1,U2 and U3 voltages showed that things were still not right on U3. I sat looking at every component on the board until I finally spotted another mistake – Q2 was also the wrong way around! I’m not sure how I made so many mistakes on this board, but hopefully this is the last one.
Rock-Mite 40 Problems
For now I’ve removed the transistor, but I don’t have any 2N7000’s in my spares box, so I’ve had to order some from eBay. These should come next week. If they do I can put a new one in and see how that changes things. With any luck I should be able to hear some CW 🙂
I decided to try and spend some time working with my Raspberry Pi this week. The first thing I wanted to do was to add an MCP23017 to the device to expand the I/O. I did this by buying the Slice of Pi I/O kit from Ciseco. This adds the MCP23017 and some pluggable headers via a PCB that slots onto to the GPIO headers on the Raspberry Pi. It comes in a kit form and needs some basic soldering skills to put it together.
The Slice of Pi I/O took about 20 minutes to put together and was fairly easy. I would recommend it as a beginner project if your new to soldering and electronics.
Unfortunately my Raspberry Pi is still running Debian, rather than Raspbian. This means I don’t have I2C support yet, so my next step is to re-install with Raspbian and test the device out.
After reviewing my Rock-Mite build compared to other peoples builds on the Internet, I noticed that I hadn’t grounded my crystal cases, so I took the thing apart again to do this. I used some segments from a paper clip to do this.
I finally got around to the smoke test with a 9V battery… and got some smoke 🙁 I unplugged straight away and checked everything. The smoke seemed to come from the back of a resistor, there was no short so I’m not sure if it was just some left over flux burning off. I tried a second bench test, and this time everything seemed okay, so I moved on to the MyDEL MP-6A I’ve bought to power the thing. Again, everything seemed fine. I tested gain and the switch on the front… and thats where things started going wrong, the Morse code for “S” beeped through my earphones, and then got quicker and quicker until it was almost a single tone, and then eventually got a small bit of smoke from Q6 (the 2N2222A). I had no antenna plugged in at this point, so the thing must have been transmitting, maybe due to a short.
Now when I plug in, I get all sorts of weird and wonderful things happening. I will plug it in, and it will produce a small amount of static through the earphones. Then eventually it will produce a …– then a single lower . tone, then …– again then it does the same thing and slows down, then it gets fast and faster until its justs a series of beeps. If I re-plug it back in straight away, or within a few minutes, I just get one series of … then it speeds up to become a continuous stream of …………….. .
I’ve emailed Dave at Small Wonder Labs and he’s started to help me work out what the problem is, but I’ve found my multimeter isn’t working so I’ve ordered a new one so I can start testing for the problem, or problems…
It turns out connecting the connector kit on the PCB was just as much work as putting the components on. It took around 3 hours.
It seemed fairly straight forward, the only issue I had was where to attach the GND to from the power supply socket, but I think I worked that one out – I’m just waiting to hear back from the supplier to see if I was correct or not. Also the gain control stuck out about 15mm too much which mean the control was too far away from the case. I fixed that with a hack saw 🙂
I’ve ordered a PSU to test it, so maybe in a few weeks I will be able to hear world-wide, or at least Europe-wide CW transmissions! I think I’m going to have to start putting some real effort into CW training now…
Well, I managed to get the rest of the components added to the Rock-Mite. I’m nearly finished. My soldering skills are now back up to what they were when I used to chip PlayStation’s and I’m already looking forward to testing this out.
And the back after I’ve removed as much of the flux as I could…
I was also thinking of making a 40M dipole to use with the Rock-Mite, but by the time I had bought the cable, dog bones and something for the centre it was just as expensive as buying a complete 40M dipole from eBay – so thats what I did, hopefully it will be delivered this week and I can start to work out how to get the antenna up on my house.
I know seasoned amateur radio enthusiasts would cringe at the fact that I’ve bought a long wire, and I can imagine that if you have a load of spare items around making a dipole would be very cheap, but at the moment I don’t have the spare items around so buying was the best I could do 🙂
The next job for the Rock-Mite is to get the connector kit connected and get it mounted in the case.