I was frustrated because I couldn't use a shortwave radio, and shortwave radios were also very expensive. After spending about half a year, I built a 6-meter single-band radio.
By leveraging my previous experience in PCB design and a period of working on embedded development, I learned and applied new knowledge continuously.😂IQ modulation, spectrum, RF amplifier circuit, impedance, PCB (printed circuit board) layout, coding, etc.
I've implemented a lot of hardware features, but the software is still lagging behind (everything has to be self-taught). We'll take it slow. After completion, I found some minor errors and shortcomings in the PCB, but I didn't have the time or energy to rework it for a second version. The main controller is STM32. The screen is a resistive touch LCD that displays a poor-quality spectrum (it can't compare to the spectrum of professional SDR devices from major manufacturers).😅), and a waterfall chart. The screen UI is still in the early stages of aesthetic design, with only a basic layout and a few fundamental control functions implemented. When powered by an external 12V power supply, the maximum transmission power approaches 10W. With the built-in battery, it should be able to reach 4 to 5 watts.
The PCB, heat sinks for the CNC machine, and 3D-printed enclosures all came from JiaLiChuang. The majority of the other electronic components were sourced from Taobao. The total research and development cost was a few hundred yuan.
The assembly and overall design quality are not very good; it's just %#.@! A few screws hold everything together. I'm worried that the internal circuitry might fail at any time, causing a fatal error.
I'm planning to get it tested soon, but I measured the harmonics and spurious emissions with my tiny spectrum analyzer, and they seem to be within acceptable limits (no more than -13dBm). However, I have a 4-stage low-pass filter at the output, which should theoretically reduce the second harmonic (around 100MHz) by 70dB. This seems strange, so I hope my tiny spectrum analyzer is inaccurate.😂
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Comparison with UVK6
Harmonic power output of tinySA test
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