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30-Meter QRP Transmitter for Morse Code

30-Meter QRP Transmitter for Morse Code

This transmitters intended purpose is for morse-code only in the 30 meter band (10Mhz). It is a low-power QRP type and needs to be connected to your existing tranceiver. The harmonic rejections on the prototype were measured at 40dB on 20Mhz and 50dB on 30Mhz.
The transmitter is build as a Colpitts Oscillator with a strong 2N2219(A) transistor. HF-output of the oscillator is 100 to 500 mW, depending on the supply voltage of 5 to 20 Volts. The transmit frequency is stabilized with the 10Mhz crystal. A slight detuning is possible by putting a 150pF trimmer capacitor between C2 and the xtal. The oscillator signal is taken from the collector of Q2 by induction and via a low-feedthrough filter and guided to the output. This particular filter is called “Chebychev” and uses standard E12 type values. The oscillator is keyed by Q1, which biases as long as the morse-key is open and the base of Q1 is at ground level. By keying the morse-key Q1 is blocked and allows Q2 to freely oscillate. For best results, use the double sided pcb as shown above. Coil L4 exists of Primary 6 turns and secundary 3 turns of 0.5mm magnet wire on a Amidon T-94-2 donut. Outside diameter is 24 mm and inside diameter is 14mm; the A(l) value is 84µH per 100 turns and permeability of 10. Q2 needs a coolrib! The whole circuit needs to be mounted in an all-metal/aluminum case. If you’re unable to obtain an all-metal case, then use a roll of self-sticking aluminum tape (available from your hardware store), just make sure that all individual pieces of aluminum-tape are conducting with each other. Works fine. Don’t forget the coolrib on T2.

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