kopia lustrzana https://github.com/RPiks/pico-hf-oscillator
86 wiersze
4.0 KiB
Markdown
86 wiersze
4.0 KiB
Markdown
# Digital controlled radio frequency oscillator for Raspberry Pi Pico
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The library for Raspberry Pi Pico includes the headers and source code and all
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necessary build files to build a custom application which turns pico into
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precise PLL digital frequency oscillator of the portion of HF radio spectrum
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1.1 to 9.4MHz with high resolution.
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# Precise frequency resolution
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The library provides about 23 milli-Hz frequency resolution. This resolution is limited by 24-bit register which is used in algorithm.
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The working WSPR beacon which has been built on the base of this project proves that the quality of generated signal is sufficient to such precise (~1.46 Hz step) frequency manipulation digital modes.
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Currently the upper freq. limit is about 9.4 MHz and it is achieved only using Pico overclocking to 270MHz.
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Here is an example of narrowband FSK (9.4 MHz carrier, 5 Hz step, 20 Hz range in total).
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# Phased locked loop in C
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The DCO uses phase locked loop principle programmed in C.
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# *NO* additional hardware
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The DCO provides the output signal on the GPIO pin. However if you want to
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transmit the signal, you should calculate and provide a lowpass filter of
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appropriate frequency. Please also figure out whether you possess rights
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to emit radio frequency energy on desired frequency.
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# GPS reference frequency correction (optional) since v.0.9
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GPS reference frequency correction option provides an absolute frequency error within about ~1Hz in long term.
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# Dual-core
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The DCO uses extensively the secodary core of the pico. The first one is for
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your ideas how to modulate the DCO to obtain a desired signal.
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The DCO does *NOT* use any floating point operations - all time-critical
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instructions run in 1 CPU cycle.
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# Radio transmitters
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Owing to the meager frequency step, it is possible to use 3, 5, or 7th harmonics
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of generated frequency. The practical resolution will be quite the same - far
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below 1 Hz. Such solution completely cover all HF and low band up to 65.8 MHz.
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# Tests of RF spectrum quality
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Sweep (5Hz step, carrier is 9.4MHz) test: https://youtu.be/nYC1VDBiz4o
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Pseudorandom MFSK (5Hz step, carrier is 9.4MHz) test: https://www.youtube.com/shorts/CEPW8hwlG7k
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There is WSPR beacon project based on this oscillator: https://github.com/RPiks/pico-WSPR-tx
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# For what?
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This is an experimental project of amateur radio hobby and it is devised by me
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in order to experiment with QRP narrowband digital modes.
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I am licensed radio amateur who is keen on experiments in the area of the
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digital modes on HF.
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My QRZ page is https://www.qrz.com/db/R2BDY
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# Feedback
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I appreciate any thoughts or comments on that matter.
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I strongly appreciate if you use this project as a part of your one in accordance with the Licence.
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I have plans of building a transceiver on the base of this library.
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The WSPR beacon is working and available here: https://github.com/RPiks/pico-WSPR-tx
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# Quick-start
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1. Install Raspberry Pi Pico SDK. Configure environment variables. Test whether
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it is built successfully.
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2. git clone this repository. cd pico-hf-oscillator ; ./build.sh
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Check whether output file ./build/pico-hf-oscillator.uf2 appears.
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3. Prepare the surrogate antenna (if you possess an SSB receiver) or pin-out
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for an oscilloscope or a spectrum analyser. The default output pin is GPIO6.
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4. Load the .uf2 file (2) into the Pico.
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5. Initialy the running frequency is 9.4 MHz.
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6. Set any other frequency ranging from 1.1 to 9.4 MHz by #define GEN_FRQ_HZ and build the project.
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7. Provide the feedback by clicking like on the github page of the project.
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Cheers,
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Roman Piksaykin, amateur callsign R2BDY
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https://www.qrz.com/db/R2BDY
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