PIC 8W Super RM Rockmite QRP Transceiver
by Bruce GM4BDJ
With some time on my hands, I decided to build a "PIC Version 8W Super RM RockMite QRP CW Transceiver” kit for 40m from China. I like a challenge.
The kit arrived quickly.
I checked using an L,C and R meter (absolutely invaluable) all resistors and capacitors. None were faulty but many capacitors were just within 20% tolerance. I didn’t feel it necessary to replace any with good ones from my hoard.
I finished the inventory with 3 ’spare’ capacitors and 7 resistors extra. Bizarrely there were two 51 ohm 2 watt looking resistors totally out of character alongside the 1/8 watt resistors used. On a personal note, I can cope better with a component or two short than having ‘extra’ ones.
As each component was tested, I stuck them into an egg carton’s edge for ease of choosing when soldering up the kit.
Construction involves winding four toroids and this was the first actual job I tackled; two are very straightforward, the other two need a bit more care. The supplied enamelled wire is not self stripping, so scraping and pre-tinning was necessary. The four toroids were the first components I soldered on to the pcb as I have found toroids often awkward to fit once the board is populated.
I used a temperature controlled soldering irons at 370C with a 1.5mm bit - and decent lead-based solder.
As the pcb has a printed component side, everything went smoothly - even the smd chip.
My built kit looks like this:-
I attached a dummy load, a powered speaker and a 9 volt battery. Inserting an iambic key resulted in some automatic cw and a power output of around 2 watts.
Attaching an aerial (40m end fed) resulted in a cacophony of 40m CW signals.
It worked, but as I’m still learning to use an iambic key, I inserted a straight key. This is where the ‘fun’ began. My straight key needed re-wiring! As well as the sleeve being grounded, the ring needs to be grounded too, the tip making the other connection.
The dreadful manual describing the operation of the PIC-controlled key circuit is incomprehensible. It was just by trial and error that I found the ‘magic’ combination for my straight key to send CW.
The iambic key was recognised easily without any pfaffling about.
According to the instruction sheet, the PIC can be programmed to send CQ with your call sign and the ability to nudge the crystal a little. I have been unable to ’translate’ the instructions to do this!
I do miss side-tone and my next project will be to fit a tiny tone generator and then get everything boxed. When I do, I’ve have a nice 4W (with 12 volts) CW crystal controlled transceiver.
I’d hesitate to recommend this kit as a first project. Try your hand at the instructions!
Frequency regulation
in the side press the SW, 3 seconds hear "di di di" sound for the first time, don't let go of SW key at this time, to hear the second after 3 seconds then "di di di", let go of the SW key. After hearing "di di" prompt, 3 seconds (don't do input after 3 seconds will automatically exit, and keep the original speed) will automatically dial key to "-" higher frequency, or to reduce the frequency of ". " After hearing "di di" prompt, can continue to toggle to the appropriate frequency, after waiting
for about 3 seconds, hear "di di di" would end configuration.
Settings are a bit difficult and still being worked on. The feed back from the Ebay Seller is ........."The settings are indeed quite complex It can be used without setting it. Use it first, and the settings can be learned slowly."
Bruce GM4BDJ