Sunday, January 24, 2010

Rock-Mite 80, first steps

The party was boring, hence I decided leave early and start building the kit instead. Actually, I essentially finished the Rock-Mite 80. Two parts I intentionally left out, C8 and R18. C8 feeds the side tone to the audio out and R18 is the emitter resistor of the 2N2222 power amplifier.

C8 is kinda obvious really... 

As for the meaning of R18, it is a 10Ohms resistor and sets the rf-output to about 0.5W. I assume that with a 100% duty cycle, the little transistor would be pushed too far. A higher ohmic resistor seems therefore appropriate. A pot or trimmer in series to the 10Ohms resistor would allow for power control, which I believe is even more important.

The transceiver is now equipped with color burst crystals. There are two reasons for doing so, the observations we lately made demonstrated that 3.5795MHz is actually a really quiet frequency and crystals for this particular frequency are well available. Moreover, many QRP kits come with color burst crystals.

In a later stage I will remove R9 again. This 4k7 resistor supplies the varicap diode with V+. The plan is to feed a voltage generated by PWM (f-set and keying) into this point. BTW, the noise source (Zener diode) which is mentioned to be at this junction is omitted in the present kit.

If you want to learn more about the Rock-Mite, check out the book below. This book made me aware of the Rock-Mites and the perfect suitability for the QRSS community:
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