This transceiver it's based on the Pititico CW transceiver originally designed by Miguel - PY2OHH and the uu80b CW transceiver designed by Roger - G3XBM. The inspiration to place it in a matchbox came from LA6NCA. This is one of the smallest and simplest transceivers designed around three 2N2222 transistors. With only a handful of components and a power output of 550mW @ 12V or 350mW @ 9V. A great project for beginners in building amateur radio transceivers. Since it's so small it will require some patience and a lot of attention. The circuit works as a low-power oscillator ( Q3 ), capable of reaching 1W and currents of 100mA ( remember that the 2N2222 is for 80mA ). The transistor handles this current well in CW, but don't keep the key activated for too long as the transistor will burn out. Another problem is operating without an antenna or a dummy load, the transistor will burn out. At some point I used a metal can 2N22222A with heatsink, but the power output was not so great so I returned to the basics and changed back to the original TO-92 version. The schematic is slightly modified from the original so it can be used with lower voltage as well. I would recommend 9V with 350mW as the transistor doesn't heat up so much. C7 allows you to tune the TX frequency. I added this one so I can tune it exactly on 7.023MHz ( see the notes in the BOM file ). L1 and C6 were added to minimize the strong AM broadcast band interferences. More details in the Blog Article. Q2 it's an audio amplifier stage. Q1 it's a simple one transistor CW bandpass filter resonating on aprox. 600Hz ( it's one transistor so do not expect miracles ). The audio output it's meant for a high impedance earpiece ( piezoelectric earpiece ). I had the best results with this one. It can also be used with regular headphones but the volume will be lower. Earbuds can be a better choice than big headphones. It has no side tone so it's more like a basic Pixie CW transceiver. The LPF on the output it's not the best but it had to fit in a matchbox. More details in the Blog Article ( coming soon ).

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