HAM

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 ...

The HFDY Active Loop is working extremely well and that too from an indoor location in MK68! Pretty awesome ;) Design I am running the loop at 5V (via a regulated linear power supply) currently where it consumes slightly less than 65mA of current. The recommended voltage is 10V, which I will shift to soon. Results I am using Airspy HF+ Discovery SDR for this experiment. ...

Setup: Si5351 RF generator (@ 28 MHz) ➔ GSD-Hacks-v5 digital amplifier ➔ 7th order LPF ➔ {COAX-UNDER-TEST} ➔ Digital RF power meter ➔ Dummy load Results 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. Designs PCB Render: Actual photo: Performance 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. ...

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! Results RX results from an experimental version of DDX: This is super useful for monitoring FT8 traffic on multiple bands. References libmirisdr-5 WSJT-X Improved

This code generates a .wav file which emulates a fully-populated FT8 band! Usage 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 rpitx. Testing I have tested rpitx on Raspberry Pi Zero 2W TX'ing @ 14.074 MHz. ...

For HF and amateur VHF bands our WiFi VFO works great. But we didn't have a cost-effective UHF signal source until now… Design 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! ...