This repository contains the source code for "QRPGuys AFP-FSK Digital Transceiver III kit": https://qrpguys.com/qrpguys-digital-fsk-transceiver-iii
as well as the mods I have originally developed for "QRPGuys DSB Digital Transceiver II Kit": https://qrpguys.com/qrpguys-40-30-20m-dsb-digital-transceiver-ii-kit with "Si5351A 160m-10m VFO Kit": https://qrpguys.com/vfo-dsb-digital-transceiver-kit
NOTE: this is NOT an official repository from QRPGuys, just my personal repository so please DO NOT contact QRPGuys regarding the source code in this repository.
The official source code from QRPGuys is available in the product page: https://qrpguys.com/qrpguys-digital-fsk-transceiver-iii and https://qrpguys.com/vfo-dsb-digital-transceiver-kit
Since the original source code from QRPGuys is licensed under GPL v3, all the source code in this repository are also licenased under GPL v3.
- main - this is a main branch, usually in sync with QRPGuys_official_releases
- QRPGuys_official_releases - this always keeps the latest official release from QRPGuys
- dsb_digital_transceiver_II_mods - this is the mods I have developed for "QRPGuys DSB Digital Transceiver II Kit" with optional "QRPGuys Si5351A 160m-10m VFO Kit" board
In 2020, I purchased the "QRPGuys DSB Digital Transceiver II Kit" with optional "Si5351A 160m-10m VFO Kit" board after someone mentioned about the kit in CalQRP club meeting before COVID-19 pandemic.
After I built the kit, I had successfully made several FT8 contacts and I was amazed by this simple kit. However, since this is a "DSB" transceiver, it of course generates "DSB" signal, meaning both "Upper Side Band" and "Lower Side Band".
Usually the modern ham radio digital modes such as FT8 and FT4 requires a PC (to run WSJT-X software) and SSB transceiver in "Upper Side Band" mode. I know it is not illegal to send the FT8 signal in DSB, but then I am using 2x the bandwidth on the valuable HF frequency.
Few weeks after I modified the NanoVNA hardware and software to make it into a SDR receiver and getting familiarized with the Si5351A Frequency Synthesizer chip, I ported the SSB modulator code of QCX-SSB to CentSDR. During the process, I learned that Si5351A can change the output clock frequencies 4800+ times per second!
While tweaking the Class-E RF Power Amplifier, I also used the PA part of the "QRPGuys DSB Digital Transceiver II Kit" to see if I can generate more power with 5V power source without DC-DC converter. Then suddenly I realized that I may be able to make this kit into a "true" FSK transmitter, just by measureing the AFSK frequency and updating the output clock frequency of Si5351A accordingly. So, I have done such mods on hardware and firmware, and it works!!
After I posted about my mods to CalQRP group, I was contacted by QRPGuys and they immediately started working on the new kit based on my mods.
Then 6 weeks later, they have officially announced the QRPGuys AFP-FSK Digital Transceiver III kit, and start selling on May 25th, 2021. They named this technique "AFP-FSK" (Audio Frequency Processed FSK).
KD1JV Steve Weber who designed the kit has already ported this "AFP-FSK" technique to his old AD9850 DDS based kit and confirmed it works great.