An SSB receiver from an Arduino/si5351 VFO/BFO

Having finished my latest Arduino Nano/si5351 VFO/BFO/Controller, I wanted to hook it up to some receiver stages to realise a SSB receiver. My grand plan for these modules is to build a multiband SSB/CW transceiver for SOTA and portable operation (another rig in my established ‘Summit Prowler’ series). The architecture will be a single conversion superhet with an IF of 12 MHz. For a base design I chose Leon VK2DOB’s MST3, a proven design which I am very familiar with, having used the MST (circa 2013) on nearly all of my SOTA activations to date.

I scratch-built two boards. The first is the MST3 product detector (SA612), audio filter (NE5534) and audio amplifier (TDA7052A). This module includes receiver muting, sidetone injection and audio-derived AGC which controls the gain of the TDA7052A. The second board contains the transmit and receive mixers (both SA612s), some SA630D RF switches to switch the bandpass filter between transmit and receive signal paths, as well as two 5-pole crystal filters (one for SSB, one for CW), each switched by another pair of SA630Ds. There is no IF gain stage, although I put some pads on the end of this board for one or two MOSFET stages, if needed.

As per other recent scratch building efforts these boards are a curious jumble of thru-hole and SOIC ICs, soldered to the copper side of a Muppet style hand drawn and etched board, largely populated with junk box and surplus sales components.

Once the boards were debugged, temporarily adding a 40m bandpass filter and connecting the VFO/BFO up brought the little receiver to life. I used no si5351 clock filtering or buffering, just CLK0 and CLK2 square waves straight into the SA612 Gilbert cell active mixers, which have some useful gain. The sound of the receiver is pleasant, to me at least. The video includes a range of DX and local signals on 40m from my QTH in the north-eastern suburbs of Melbourne, received over a day.
Next, I will add a third board with a bank of switched bandpass filters and switching logic, all controlled by the Arduino. More to follow.

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2 thoughts on “An SSB receiver from an Arduino/si5351 VFO/BFO

  1. Do you have a schematic? I’m mainly needing one for a minimalist receiver using a SA612. So just really the antenna circuit and SA612. I have a QRP Labs DDS VFO. I’ll manage the audio stuff with parts I have.

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    • Paul Taylor says:

      Hi Michael, your QRPLabs VFO will be perfect, probably functionally equivalent to my VFO which is based on VU2ESE Raduino. No buffering or filtering, just ‘naked’ si5351 square wave clocks into the SA612 mixer and product detector via a 100pf capacitor. So simple, and surprisingly good performance.

      My receiver is based on VK2DOBs Minimal Sideband Transceiver. Circuits are freely available at http://www.ozqrp.com/download.html under the MST3 Manual Ver 1 button. Leon offers his excellent design and instructions openly. I will sketch up the BPF and first mixer and add it in the next day or so anyway. I used Leon’s BPF but the ones on Kitsandparts are also very good and easily reproduced.

      My IF filter is on 12MHz (not 10MHz as per Leon’s design) so that I can get 30m.

      Good luck! Paul VK3HN.

      Like

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