After weeks of waiting for the replacement zener diode I had to order after the power connector brushed the PCB, I finally got to replace it and put it into it’s enclosure.
I also changed C8 in an attempt to attenuate the ear-splitting side tone and fitted a power indicator.
Within seconds of firing it up, I heard HA6OD calling CQ not too far from the xtal frequency. I replied and had a 1000 mile QSO using 400mw.
I’m still gobsmacked 
I couldn’t wait for my diodes to arrive, so I scavenged a 1n4007 from an old bridge rectifier.
For some reason, I couldn’t get enough solder out of the holes on the board, so I had to drill them out – which unfortunately delaminated the track below. I managed to kludge them together and temporarily replace the track with bellwire.
With trepidation, I checked the polarity on the power connector, plugged it in and fired it up. I was very happy to see the LED light and the receiver burst into life again.
Phew. Lesson learned. I hope.
Last night, I reversed the polarity on my MFJ 9020 QRP rig.
What, that noise? That was the sound of:
1. My head hitting the shack desk.repeatedly
2. A diode going POP!
3. A trace on the PCB blowing off the PCB.
Boy, do I feel a nerk. Repairs have begun, a rectifier diode next to the dc input (D7 on this diagram, page 16) has been melted into a piece of wire, so I snipped it out and ordered some more.
The rig was off when I plugged it in so I’m hoping it’s just the diode and
PCB trace I need to repair.
It occurred to me that I’d never built a crystal radio. That seemed pretty silly, especially when they are going to go digital and turn off the medium wave broadcast stations.
Here is my attempt, on youTube:
I made it three days ago and I’m still listening to it
I recently invested in an MFJ 9020 20m QRP rig. It outs out about 4.5 watts, and the receiver is lovely.
I’ve made a couple of really good contacts with it so far – K1GCD 3100 miles away (Thanks for the QSL card Jim!) and W8TA, 3600 miles away, which I think is pretty amazing considering that it’s just going into a wire antenna.
Mine didn’t have the keyer option, so I’ll just have to make the arduino based one I’ve been contemplating for a while now…
Yay! Another rock-mite-tastic QSO with Colin G0XCF this evening, 168 miles on just a watt and a bit.
Still a little ways to go before I beat the 460 miles which is my previous record, with GM4JYB in Caithness though. With conditions (and my meagre CW skills) improving, I’m sure I’ll smash it soon.
This is a simple CW cheat sheet that I use when I get the dreaded brain-freeze mid QSO. I can never remember how to report chirp, or sometimes I forget to sign off properly… I have this sat on my desk in front of my rig just in case, and I thought it might help some folks.
After a bit of post-upgrade research, it turns out my choice of transistor was sub-optimal, and prone to harmonics at 7 MHz, so I swapped it out for a 2N3553. This cost about four times as much as the previous one. It now puts out a whole 1.2 WATTS! Still no QSOs as yet but I’ve only been trying half an hour or so, and I’ve got heavy toddler QRM 
Today, I replaced the PA in my Rock Mite 40 with a 2N3053 which, when the biasing resistor is shorted out, gives me 1 watt of output.
I fired it up, and within minutes I was in QSO with GM4JYB 450 miles away. It was hard going as I was using a small speaker which really wasn’t up to the task, but we managed a few overs that I managed to get the gist of.
It’s amazing – I thought these QRP radios were just curiosities, but they are perfectly functional and enjoyable to use.
After reading an article in the latest Radcom, I decided to have a look at the Small Wonder Labs Rock Mite 40. At £19, the kit includes the PCB and all the components sans the connectors, and has an electronic inbuilt keyer! I ordered the optional connector pack which includes a BNC connector, power connectors, 3.5 micro jack connectors, AF gain pot and a diode for reverse polarity protection (which I thought they should have included in the main kit).
I managed to assemble the PCB in one evening, though I must admit I did a messy job on the single SMB component (the mixer chip). Eventually, I had to cut the solder bridges I had made with a stanley knife. Fortunately, I have access to some quite powerful microscopes where I work, which enabled me to make an electrically effective connection, even if it was a bit messy:
Eventually, I got to the “smoke test” stage, and I fired her up. I didn’t manage to release the blue smoke, and heard many lovely CW signals! All that remained was to put it in some sort of enclosure.
Originally, I had decided to use an Altoids tin, but the eBay vendor I bought it from let me down, so I sorted through my junk box and found a screened case from a Coventry Amateur Radio Club project that I never completed. This turned out to be a blessing in disguise, as it turned out quite pretty I think, especially with a little laser etching:
I connected the power, key, antenna and phones, and fired her up. Within minutes, heard a CQ call from G3HAL. I didn’t expect much as my tuner was registering roughly 250mw output, but I replied… and got an answer!!! We managed a short QSO before QRM killed our conversation (the RM40 is not well known for it’s selectivity) but from that moment on, I was hooked: I made a contact with a rig, antenna and key that I’d built myself 125 miles away with 300mw!!!
I recommend this kit to any radio amateur. It’s so much fun, it should be illegal!!! I intend to get a couple more for other bands, and do a simple VXO mod on this one to bring it closer to 7.030 (Mine transmits on roughly 7.02809/7.02892).
Stop reading this and go and buy one.