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. ...
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/
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. ...
I recently spotted the Tokmas CI7N170SM TO-247 part on LCSC. It seems like a pretty neat part for building non-QRP HF amplifiers! This could be a better part for our Baby QRO amplifier. Datasheet excerpts: The full datasheet is available here. In comparison, here is how a professional RF part (MRF300AN) looks like: That 272W maximum power dissipation figure is crazy good but switching characteristics are not that great (fast).
Here is the FT8 WAV test file. On an AMD64 machine: 1 second using the fast decode settings. We were able to get the MSHV's FT8 engine to work on Android, thanks to the work done by https://github.com/sannysanoff/SDRPlusPlusBrown folks. Around ~4.5 seconds to decode the same file. This is why we can't really have full-blown realtime FT8 decoder(s) on Android just yet! Idea: But we can surely use this full-blown FT8 decoder in our FT8 Decoder app which has no realtime requirements! ...
OCXO's are awesome - this is what I learned while trying to get WSPR working reliably on the 2m band. Here is all you need for reliable WSPR'ing on the 2m band: A RAW OCXO "can" works fine too! Note: This modded Si5351 board image comes from https://www.simonsdialogs.com site. Essentially we are modding the CLK2 output port to become an input port which accepts the OCXO's output signal. ...