Building and controlling the Pi Pico RX

Some time ago I was handed a free Pi Pico WH processor board.
To test what it could do, I made a simple webserver with it, and it worked ... but I got bored, what would I use it for ? I had no direct application for it.

Somewhat later, I found this online article : https://101-things.readthedocs.io/en/latest/radio_receiver.html  , by Jon Dawson, KD4RES.

Aha! This looked more interesting.
The article describes an HF receiver with minimal hardware and some nice features. Read the full article if you want to find out how it works.

The receiver needs no WiFi, so I ordered a couple of basic Pi Pico boards without WiFi.
The software for the Pi Pico can be found on Jasons' Github page and is very simple to program, just drag the correct file to the Pico like you would do to copy it on a flash drive.

There are versions on Github for the basic Pico (2040 CPU) and for the Pico2 (2350 CPU), see Releases

Still later, there was an article in the Belgian ham magazine CQ-QSO (January 2025, pages 11-13), by a French ham : Anthony, F4GOH. It described a ready made PCB to facilitate building this receiver.

All info is on his Github page , it contains two projects : a simple board for a QSD Detector (Tayloe detector), and the full Pi Pico board I am using.

My good friend Gil, ONL12523 (you may know him from our OST Morse Box and Forty-Niner PLL projects) was prepared to have the circuit boards made in China, and prepare them with the SMD components.

From there, it was only a little work to build a couple of these receivers. The first one was built for a friend, and looked like this:

It was built on a U-shaped chassis made from pieces of PCB. It includes a built-in Li-Ion cell (1800 mAh) with a charger board. There is no filtering at all at the receiver input, so for best results, external bandpass filters can be added.

When everything worked,  I bent a piece of metal (from an old instrument case) to close the box. It is attached with 4 Parker screws in the sides.

This receiver changed owner, so I had to build a second one for myself. 
This time I took  a slightly different approach.

I built a flat box out of PCB pieces, put the encoder on the side, and since everyone always asks "Can we see what's inside?" ... I made a clear cover out of an old CD jewel case.

The cover is press-fit between the left and right sides, so opening it is also very easy.

This also saved me the tedious work to drill and file a rectangular hole for the OLED display.

The two buttons for MENU and EXIT, which are on the PCB were extended with two plastic spacers, where I drilled a fitting hole in the bottom. This way I can reach the buttons through the plastic cover. The rotary encoder is soldered between two small pieces of PCB, which are in turn soldered to the chassis.

Here some pictures of the sides of the box.

Right side with encoder and antenna input (BNC).

Back side with ON/OFF switch and USB-C connector for charging the 1800 mAh Li-Ion cell.

Left side with USB-C connector of the Pi Pico, and the audio output for headphone or external amplified speaker.

Using the Pi Pico Receiver

Even without any filtering , it's amazing what you can do with this receiver. See the user manual and check all the possibilities here

Using my long wire antenna, I get good results on longwave, medium wave and shortwave. 
The only strange effect I noticed, is a kind of "motorboating" noise when no signal is present.
But once a station is tuned in, the noise disappears, so it's not a big problem. 
The results still exceed my expectations, for a receiver that costs less than 20€.

Control Software - Work in progress ... 

Remembering all the combinations of buttons to control this receiver is rather cumbersome, so again we got the help of goood friend Gil ... He has made a basic CAT control program.
It's still in its' beta version, but it's already looking good !

At the moment, it contains a few favourite fixed frequencies, and it can set any frequency via the input box. The small rectangle at the right shows the CAT commands being sent.
Next to the frequency display, the MODE can be set.

At the bottom, the COM port can be selected and the connection can be opened or closed.

You'll have to come back later if you want this program, I'll publish it on my Github page when it's ready.

73,

Luc ON7DQ