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RPiks authored Dec 10, 2023
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The library for Raspberry Pi Pico includes the headers and source code and all
necessary build files to build a custom application which turns pico into
precise PLL digital frequency oscillator of the portion of HF radio spectrum
1.1 to 9.4MHz with high resolution.
precise PLL digital frequency oscillator of the whole of HF radio spectrum
(1 Hz to 32.333 MHz) with millihertz resolution.

# Precise frequency resolution
The library provides about 23 milli-Hz frequency resolution. This resolution is limited by 24-bit register which is used in algorithm.
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.
Currently the upper freq. limit is about 9.4 MHz and it is achieved only using Pico overclocking to 270MHz.
The upper freq. limit is ~32.333 MHz and it is achieved only using Pico overclocking to 270MHz.

![mfsk-spectra](https://github.com/RPiks/pico-hf-oscillator/assets/47501785/a8309813-8e77-407e-abfc-58cbd262c35c)

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# Radio transmitters
Owing to the meager frequency step, it is possible to use 3, 5, or 7th harmonics
of generated frequency. The practical resolution will be quite the same - far
below 1 Hz. Such solution completely cover all HF and low band up to 65.8 MHz.
below 1 Hz. Such solution completely cover all HF and VHF band up to ~233 MHz.

# Tests of RF spectrum quality
Sweep (5Hz step, carrier is 9.4MHz) test: https://youtu.be/nYC1VDBiz4o
Pseudorandom MFSK (5Hz step, carrier is 9.4MHz) test: https://www.youtube.com/shorts/CEPW8hwlG7k
Sweep test: https://youtu.be/nYC1VDBiz4o
Pseudorandom MFSK test: https://www.youtube.com/shorts/CEPW8hwlG7k
There is WSPR beacon project based on this oscillator: https://github.com/RPiks/pico-WSPR-tx
![image](https://github.com/RPiks/pico-hf-oscillator/assets/47501785/fd9b0eac-1900-43d0-bf83-3d95a7cbd87a)


# For what?
This is an experimental project of amateur radio hobby and it is devised by me
in order to experiment with QRP narrowband digital modes.
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4. Load the .uf2 file (2) into the Pico.

5. Initialy the running frequency is 9.4 MHz.
5. Initialy the running frequency is 29.977777 MHz.

6. Set any other frequency ranging from 1.1 to 9.4 MHz by #define GEN_FRQ_HZ and build the project.
6. Set any other frequency up to 32.333333 MHz by #define GEN_FRQ_HZ and build the project.

7. Provide the feedback by clicking like on the github page of the project.
7. Provide the feedback by clicking like (`a star`) on the github page of the project :)


Cheers,
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