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)
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. ...
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/
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. ...
This code generates a .wav file which emulates a fully-populated FT8 band! This .wav file can then be played with rpitx on actual air (well on a dummy load) for receiver testing purposes. rm mixed.wav; sox -m *.wav mixed.wav sox mixed.wav -r 48000 sampleaudio.wav Now play sampleaudio.wav using https://github.com/F5OEO/rpitx. I have tested https://github.com/F5OEO/rpitx on Raspberry Pi Zero 2W TX'ing @ 14.074 MHz. References: ...
For HF and amateur VHF bands our WiFi VFO works great. But we didn't have a cost-effective UHF signal source until now… Thanks to Ismo (OH2FTG), we recently experimented with a HopeRF CMT2119A powered board called HOPERF RF module RFM119W-433S1. Here is the CMT2119A powered board in action producing a CW (OOK) signal at ~433 MHz. The stability is pretty good and a bit surprising considering that the board uses a 20ppm 26 MHz regular quartz crystal - not bad! ...
Instead of punching islands or using commercial pads (islands) or making traditional pads myself, I simply make use of small pieces of single-sided PCBs to create the pads / islands easily for my boards. This technique has a huge advantage over the punched islands or scored and divided boards techniques as it keeps the bottom ground plane perfectly 100% intact! Also, it is almost a tool-free process to create the pads by breaking or cutting the single-sided PCBs. Single-sided prototyping boards also happen to be very reasonably priced. ...