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Polar Modulation for the masses We have been working on generating SSB signals using Polar Modulation. Hardware stack: RP2350-Zero MCU board + Fast Si5351 module + AP63301 buck regulator (for 5W mode). Please see https://github.com/kholia/PolarModulationSSB for more details. The audio fidelity and general quality is ok'ish at the moment but it can only improve from here. We are yet to hookup the amplitude ("envelope") restoration part. Motivation Why should Guido, Hans, and FlexRadio folks have all the fun? ;) ...

I recently worked on a PA0FRI Active Antenna design with fast BFR93A / BFR106 transistors. Design 3D render: Schematic: Previous Next     / [pdf] View the PDF file here. Simulation Results ...

Description We have built the simplest, power efficient and 'ready-for-solar' APRS Digipeater and iGate on a MCU (RPi Pico 2 W)! Our existing KISSLink v1 BLE KISS TNC device is capable of running in standalone mode with an alternate firmware! Goal(s): Our design prioritizes low power, reliability, and unattended deployment over flexibility. And yes, we want to do this with cheap, widely available BaoFeng radios. This means a couple of things: ...

Description We have built a Bluetooth-enabled and APRSdroid-compatible digital interface (KISS TNC) for less than 15 USD (for the fully-loaded make including cables). We call it the KISSLink v1. This digital interface can be powered from the USB 5V or the inbuilt battery. Schematic Previous Next     / [pdf] View the PDF file here. RX path simulation (AF front-end) ...

The design Here is a "safe" APRS interface for BaoFeng and other radios. Sample schematic: Previous Next     / [pdf] View the PDF file here. Render ...

Idea Ismo recently shared the https://github.com/CoolNamesAllTaken/adsbee project which is pretty cool. Challenges The ADS-B (Automatic Dependent Surveillance-Broadcast) system uses a data rate of 1 Mbit/s (1 megabit per second) for its aircraft position and identification transmissions on the 1090 MHz frequency. This is too much for HOPERF CMT2300A and related transceiver chips unfortunately! This got us thinking about the following VFM ADS-B RX chain. Architecture Here is a simple ADS-B RX circuit description. ...

Ismo (OH2FTG) has praised the STM32's ADC quality multiple times, and I finally decided to give it a go. I usually stick with Waveshare RP2350-Zero boards, but the RP2350 ADC performance is limited to under 10 ENOB. With the STM32H562RGT6, we're able to achieve ~13 ENOB using 16× hardware ADC oversampling, with potential headroom to push this even further. By sampling the Si4732's SSB output using the STM32H562RGT6 ADC and exposing the audio samples to the host via a "virtual" USB UAC-2 device, we get the following RX results: ...

The PE4312 is a 50Ω, 6-bit RF digital step attenuator available for around 2 USD. Pretty neat for implementing real digital AGC! For half-the-price we can get the alternate Archiwave ARW637 or ARW621A ICs which work very similarly to PE4312! References: Archiwave ARW637 Archiwave ARW621A

This short article describes a flight-safe power supply for FieldOps. Component List Simply get these: USB QC/PD AFC trigger decoy board (9V) USB QC/PD AFC trigger decoy board (12V) USB QC/PD AFC trigger decoy board (15V) Xiaomi Pocket Power Bank Pro 10000 33W This one does 9V, 12V, 15V and 20V without any problems. OR A 65W USB PD power bank - not needed for 5 to 10W QRP FieldOps ...

What This Article Covers This article presents a practical journey to add Linux support for the HOPERF CMT2300A Sub-GHz RF transceiver - starting from extracting register configuration tables out of vendor firmware, to building and testing a Linux driver on real hardware. You'll learn: How TP-Link's driver situation motivated this effort How firmware was extracted and analyzed How to build and load the custom driver on Raspberry Pi How to verify real on-air packet RX This is aimed at embedded Linux developers, reverse engineers, and RF hackers. It is not a beginner Linux kernel tutorial nor a full CMT2300A datasheet walkthrough - focus is on practical bring-up and reproducibility. ...