My Rockmite 20 took a final shape. I have managed to kit it up and do a first run these days and its working almost great. I have added the 2N3866 power transistor from the kit to increase the output power, replaced R5 with a 1M potmeter for volume control and added a small VXO to have a little bit of tuning range.
Update on 06.05.2015. CNC engraved panel labels:
The VXO mod is this one from KE2SP. With it I am able to tune the frequency from around 14.047 to 14.050, with an acceptable Tx/Rx offset. I have made a test QSO with a local ham and seems to be ok. The bad part with this mod is that at Rx, the crystal front end filter is to narrow, and when coming to 14.047 its quite noticeable. I read on the Rockmite yahoo group that a best way to solve this is to replace C2 with a 68pF one. I will be testing this out later.
Still don’t know what crystal to chose. I have a 14.060 pair too, but don’t know if it will be more traffic chances there rather than 14.050.
The power mod I did was to put instead of the 2N2222, a 2N3866 supplied in the kit, and replaced R18, 10 ohms, with a 3 ohm one. I have measured the power output with 2N3866, at around 12.3 V and it seems to be low, around 300-350 mW. Not sure if this is ok, I should probably increase the supply voltage to 13.8 V and see then the result, or maybe to lower R18 to 2.2 ohms or even 0 ohm.
For power supply I have used a 12 V SLA battery. Its very silent with it. First test was with a linear power supply, 220V/12V with a LM317, but a lot of noise was coming to the receiver.
I haven’t done yet any QSO, except that sked with a local ham to test it. One night when I was finishing assembly everything and did the first smoke test, I was calling CQ for about two-three minutes, and also posted myself on the cluster, with no response of course. But the next day, curiously, I search myself on DXsummit.fi, and found this report from VE7DXF, 339, 9000km away, wow… So it may be promising!