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. ...

Shipping hardware internationally is a hard, labor intensive, and overall a frustrating process - especially more so these days. Here is our plan to supply the DDX to customers: Make the hardware files free / low-cost. The users will be able to order fully assembled boards from JLCPCB or other vendors on their own. Required a small licensing fee for the software firmware part. This is how we get to keep the hobby self-sustaining! ...

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).

While running https://github.com/fhoedemakers/pico-infonesPlus, I found that my SNES gaming pad was not fully supported. Specifically the UP DOWN and LEFT RIGHT keys were not working. Let's debug this a bit: Plug in the gaming pad on a Linux box and run the following command (hidraw5 will need to be changed as needed): $ lsusb ... Bus 001 Device 063: ID 0810:e501 Personal Communication Systems, Inc. SNES Gamepad $ sudo hexdump -C /dev/hidraw5 ... 00004a50 01 80 80 7f 7f 0f 00 00 01 80 80 7f 00 0f 00 00 |................| 00004a60 01 80 80 7f 00 0f 00 00 01 80 80 7f 00 0f 00 00 |................| * 00004a80 01 80 80 7f 7f 0f 00 00 01 80 80 7f 7f 0f 00 00 |................| This is what I see when pressing the UP key. ...

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. ...

Circuit: DDX-Commercial-7 Antenna: Small jumper cable attached 10m: 36 dB on WSJT-X audio meter, on quiet and also with nearby beacon on !!! 12m: 36 dB on audio meter, on quiet and also with nearby beacon on !!! 15m: 46 dB on audio meter on quiet, 65 dB with nearby beacon on - OK 20m: 44 dB on quiet, 65 dB with beacon on - OK 40m: 40 dB on quiet, 60 dB with beacon on - OK ...