The SimpleSSB - A Homebrew Single Sideband Amateur Radio Tranceiver

In early January 2021 I obtained my Advanced level certification for Amateur Radio (in Canada). One of the things that this allows me to do is to build radio equipment that can transmit on the amateur radio bands.

That is something that I have always wanted to do but I never had the ambition, time or qualifications before now.

To begin with I thought I would build something really simple and decided on a low power transmitter for WSPR (Weak Signal Propagation Reporter). That actually ended up being really easy with the exception of having to build a low pass filter to remove harmonics from the transmitter output in order to stay within the regulations.

In researching how to do that I came across the YouTube channel and Blog website of Charlie Morris who is a Amateur Radio operator and experimenter extraodinaire in New Zealand.

I followed Charlie’s building technique for the low pass filter and while I was doing that he started a new video series on YouTube about building a Simple SSB tranceiver from scratch with goal of using components that are easy to obtain. That was great for me because I didn’t have junk box of RF components because I have mostly worked with digital electronics up until now.

Charlie’s videos aren’t tutorials as such but instead are more about concepts, design information and testing. That is exactly what I needed and I was hooked!

One thing that really appeals to me about Charlie’s approach is that he typically divides his designs into modules each of which can be built and tested individually. He uses strip board (also known as veroboard) to build the modules and then mounts them and wires them together on a bare copper clad circuit board that acts as a mechanical base and electrical ground plane. You can get a good idea of how this is accomplished from the photo above and the ones below.

As it turned out I had great success with this approach and no problems at all with noise or instability. It even all still worked when I put it inside a box which I think is not often the result!

I did make a few changes to the design along the way because my goal was to only use the SimpleSSB for digital mode communications and in particular with the mode JS8. That meant I didn’t have to bother with the audio output section or auto level control since for the digital modes you mostly bypass all that anyway. I also changed the frequency to the 40m band from 80m as JS8 is most popular on that band.

I had to change the IF frequence to 8MHz because I could only find 8MHz crystals to build the crystal filter. I thought that might be a problem but it wasn’t.

I didn’t bother with any physical user controls or displays and instead I used a small ESP32 microcontroller as the processor and access it via WIFI with it running a simple web server with the controls available on that.

The computer for digital mode encoding and decoding is a Raspbery Pi 4B and the power supply portion of the radio also supplies 5.2V at 5A for the Pi. The input voltage for the whole system is nominally 24V which means it can be powered directly by 6 cell LIPO or LION batteries which I already had.

The Pi automatically becomes a WIFI access point when there is no other WIFI available and in that situation the ESP32 connects to it. I can use a laptop or tablet to connect to the Pi if out in the field. At home I typically use remote access to the Pi from my PC or laptop.

The following photo shows the individual modules a little better and the arrangement shown sitting on the bench worked just fine.