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Description: Recently, there has been a renewed interest in QRSS, which is a very slow Morse code transmission method. Previous experimentation involved developing software to record audio and generate the necessary Fast Fourier Transforms (FFTs) to decode lengthy Morse messages. The circuit primarily consists of a Colpitt's oscillator, enhanced by a reverse-biased LED that provides additional capacitance to adjust the frequency around the nominal crystal frequency. Initial tests utilized an Arduino equipped with a digital-to-analog converter to control the LED capacitance, yielding satisfactory results. Although the circuit was never deployed for actual transmission, there is contemplation of building a new version to leverage the lessons learned. Proposed enhancements include integrating a small dummy load (a 50-ohm resistor) and adding test points for monitoring supply voltage and current, possibly sourced from an Arduino. Monitoring temperature is also being considered. While a standard 30m dipole antenna could be used, there is interest in exploring a more compact design, inspired by Alan's experiments with a center-loaded short dipole. The micro-power transmitter is engaging and poses minimal risk of interference, yet achieving long-distance communication may be challenging. Plans to increase power output include using a higher voltage source, incorporating a buffer and power amplifier to reach an output of 100-200 mW, and implementing a harmonic filter to ensure compliance with regulations. A kit that encompasses all these features is available for approximately $15.

The proposed QRSS (Quasi-Random Slow Speed) Morse code transmitter circuit is centered around a Colpitt's oscillator, which is known for its stability and simplicity in generating oscillations at radio frequencies. The incorporation of a reverse-biased LED as a variable capacitor allows for fine-tuning of the oscillator frequency, enabling it to operate optimally around the crystal's nominal frequency. This innovative approach not only enhances frequency stability but also adds an element of flexibility to the design.

The use of an Arduino with a digital-to-analog converter to modulate the LED capacitance is noteworthy. This setup allows for real-time adjustments to the oscillator's frequency, making it suitable for decoding slow Morse transmissions. The integration of software for audio recording and FFT analysis provides a comprehensive solution for decoding Morse code, even from extended transmissions.

Future iterations of this project are set to include several key enhancements. The addition of a 50-ohm dummy load will facilitate testing and tuning without radiating signals into the environment. Test points for monitoring supply voltage and current will provide valuable data for optimizing performance, particularly when powered by an Arduino. The consideration of temperature monitoring will further enhance the circuit's reliability by allowing for compensation of frequency drift due to thermal variations.

Regarding antenna design, while a standard 30m dipole is a viable option, the exploration of a center-loaded short dipole may yield a more compact and efficient solution for QRSS transmission. This could potentially improve the transmitter's performance in various operating conditions.

To enhance transmission power, the design will incorporate a higher voltage power supply, along with a buffer and power amplifier capable of delivering 100-200 mW output. This power increase will significantly improve the range of the transmitter while maintaining compliance with amateur radio regulations through the use of a harmonic filter. The availability of a pre-assembled kit containing these features at a reasonable price point simplifies the development process and allows for rapid prototyping and experimentation. Overall, this project represents an exciting opportunity to delve deeper into the world of QRSS and Morse code communication while leveraging modern electronic components and techniques.For some reason, I`m getting back into the universe of QRSS, or very slow Morse code. I goofed around with this for a while, writing some software to record audio and produce the necessary FFTs so that you can read Morse from these incredibly long Morse messages, but lately haven`t done much lately. It`s really just a Colpitt`s oscillator, with a reverse biased LED acting as additional capacitance to tune  the frequency around the nominal crystal frequency. When I built this circuit, I played around a bit with using an Arduino with an digital to analog converter to drive the LED back capacitance, and that worked fairly well.

Here`s a timewarp back to that project, in the form of two of my earlier YouTube vids: It worked, but I never put it on the air. But I got to rethinking it a bit more, and thought that maybe I`d assemble a new version and see how much I learned.

I`ve got some ideas for improvements: Build in a small dummy load  (just a 50ohm resistor), and add some test points so you can monitor the supply voltage and current from (say) an Arduino. It would be interesting to monitor temperature as well. I also was considering making a better dedicated antenna for it. I suppose I could just use a 30m dipole, but I think it might be fun to try something a bit smaller. Alan did some experimentation with a center loaded short dipole which might be fun, but I`m still pondering that.

The micro-power transmitter is fun, and unlikely to cause anybody any anguish, but might also be a bit hard to get any real DX with. So, I started thinking about what I needed to change. Higher voltage, to generate more power. A buffer and power amplifier to generate maybe 100-200mw. And a harmonic filter, so I could be a good citizen. But then I realized something: Hans was offering a kit that had all of those features already, and for about $15 US.

So, I`ve got one of those on order too.