Related articles: Proper Single Transistor LNA for HF A Sustainable Radio Design? We are finally going to build a QSD RX! Here is the rough schematic I am thinking about: References: https://www.n6qw.com/MC1496.html https://github.com/steve-m/hsdaoh-rp2350 (see internal_adc section) This way we can continue using RP2350 instead of moving to something like STM32H5 immediately https://github.com/dawsonjon/PicoRX/tree/master/simulations (also for DSP code)
This note demonstrates a small connectivity tester / check nets program for KiCad. This program allows doing checks like: Is the U1:8 pin connected to GND? Sometimes visual errors can creep in the schematic (and the PCB subsequently). This connectivity tester allows expressing the same connections in a non-visual way (with a different probability of making errors). The ERC and DRC checks in KiCad work great but this non-visual test assertions provide another level of sanity checking. ...
Setup: Si5351 RF generator (@ 28 MHz) ➔ GSD-Hacks-v5 ➔ 7th order LPF ➔ {COAX-UNDER-TEST} ➔ Digital RF power meter ➔ Dummy load Results at 13.8V drain: Coax Type Power Reading RG-58 (7 meters) 4.5W RG-316 (7 meters) 3.9W RG-188 (7 meters) 3.9W Results at 15V drain: Coax Type Power Reading RG-58 (7 meters) 5.4W RG-316 (7 meters) 4.7W RG-188 (7 meters) 4.7W These measurement results seem to match the ones from Eric, WD8RIF. ...
Here is the schematic for a standard 50Ω LPF for the 12-11-10m bands. PCB Render: Actual photo: NanoVNA results of the PCB build: Build Notes: These values come from RobG (https://hackaday.io/) Shunt C: 100pF Series L: 12T on T37-6 core, 11T on T50-6, making about 485nH Shunt C: 180pF Series L: 13T on T37-6 core, 12T on T50-6, making about 580nH Shunt C: 180pF Series L: 12T on T37-6 core, 11T on T50-6, making about 485nH Shunt C: 100pF Winding wire size: 27 SWG (is non-critical) Note: We needed to reduce 1T (from the values specified above) when using the T50-6 cores. As usual, use a DE-5000 LCR Meter (or better) to know the exact values. ...
Note: This HF LNA design is inspired by PY2OHH designs and mcHF work. Previous article: Single Transistor LNA for HF - it cut a corner when it came to output impedance matching ;) The idea that a single-transistor-preamp with 10 dB gain is more than enough for HF comes from Gajendra Kumar (VU2BGS). As a new "designer" I am often overwhelmed by the different possible design paths - so having guidance from an elmer becomes crucial. ...
My solar powered WSPR beacon is now active on the 12m band! Tech stack: Navitas 100W Solar Panel, Exide Solar Blitz 40AH battery, Skypearll Solar Charge Controller 30A, 200W 20A DC-DC CC CV Buck module (Robu) - set to output 7.5V, Waveshare ESP32-S3 Zero board, Si5351 with 0.5ppm TCXO, GSD-Hacks-v5 amplifier, DFRobot Gravity Digital 5A Relay Module Photos of components involved (for reference): ...
Setup OS and SDR Please use the latest Raspberry Pi OS 64-bit on RPi 4 or later. Using a Raspberry Pi (<=3) is NOT recommended as it has quite a bit of power supply noise on the USB ports, which reduces the performance of the connected SDR. Install dependencies: sudo apt-get update sudo apt-get install airspyhf \ soapysdr-tools sox libsox-fmt-all wsjtx \ pulseaudio-utils git vim fluxbox xterm tightvncserver sudo apt-get install cmake pkg-config \ libusb-1.0-0-dev \ libasound2-dev \ libairspy-dev \ libairspyhf-dev \ librtlsdr-dev \ libsndfile1-dev \ portaudio19-dev \ libvolk-dev Build airspyhf-fmradion SDR software: ...
WSJT-X 3.x has inbuilt support for band hopping! RX results from an experimental version of DDX: This is super useful for monitoring FT8 traffic on multiple bands. References: https://github.com/kholia/libmirisdr-5 https://sourceforge.net/projects/wsjt-x-improved/files/
My old Luminous Zelio inverter (bought in ~2013) lasted for close to 8 years. Trusting the Luminous brand, I installed two more Luminous Zelio inverters in year 2024 in two different homes. Come year 2025 and both these Zelio inverters have conked off and that too in less than a year! I guess they don't make the Zelio inverters the way they used to :-( For now, I have shifted to Microtek Heavy Duty UPS 1750 and Microtek 1275 12V SW inverter models.
Future radio receiver design ideas (from Ismo, Pete and other folks): Antenna ➔ (BPF) ➔ BFR93A based pre-amp from mcHF project ➔ MC1496 (Mixer) ➔ 455 kHz IF ➔ Ceramic filter SMD (HCI) ➔ 'IF amplifier' (20-40 dB gain?) ➔ Overclocked Pico 2's ADC (3+ MSPS) ➔ Digital down-conversion and processing in digital domain ➔ Expose the processed audio samples over USB (Pico 2 acts as a sound card). Benefits: This enables reception of SSB and CW signals! The 455 kHz IF with digital processing gives us the best of both analog selectivity (ceramic filter) and digital flexibility. ...