You are currently viewing S21RC Digital Interface Rev 2.0 (Ham Radio – Computer)

S21RC Digital Interface Rev 2.0 (Ham Radio – Computer)

Too many of us just connect the audio from the computer to the radio without realizing why the audio has distortion or why the computer is acting. So if you use just two simple 3.5mm stereo plug to connect your HF/VHF radio with the computer for echolink or HF digital modes like FT8/FT4 etc- think again.

The interface made in 2021 (V1.5) was a great success, More than 7000 digital QSO was done with it with several different rigs. No clutter of cables to the computer and radio. Only one USB connects to the computer and two cable for Remote (ICOM CIV) and Audio to the Rig. Due to the complete isolation the tone was crisp and no more computer problem due to RF leakage even for QRO. V1.5 had three separate modules needed to connect on the main board, mainly a USB HUB module, a USB to TTL converter, and a DAC/ADC (soundcard). The audio was isolated using isolation transformer and the remote CAT and PTT optically isolated using optocouplers. REV2.0 has all the chip onboard and no need for different modules.

Recently one local ham friend asked me to build one for him – so I thought it’s time I make a compact single board with all the components together so anyone can reproduce it. It’s a no brainer, just put the parts and connect the wires as per description.

Galvanically Isolated Audio.
Optically isolated PTT.
Optically isolated CAT interface (RX/TX or CI-V)

Two downstream ports of SL2.1 IC used for the USB distribution, audio is handled by the CM108 IC, and a CH340G doing the USB/TTL conversion. The TLP241-4 is the 4 channel optocoupler.

For ICOM CI-V the Jumper should be used to short RX and TX CAT command, Do not use the jumper for other radio having separate RX/TX CAT.

Click HERE to download the Gerber file for fabrication.

(will be updated after final tuning).

Download Large Size from here.

BUY (inside Bangladesh only):
The PCB costs me 20$ for 5pcs to get made from China. I have few PCB left, if you want one you can get it for 400/- Taka each [Local HAM in Bangladesh only – no shipping abroad]. Drop me an email to book it.

If you need the full kit (all component soldered – you only need a micro USB cable and appropriate cable/jack for your radio) it will cost you Taka 2200.00 (Bangladeshi local HAM only – no shipping abroad).

Apart from countless hours (and lots of coffee) to design the circuit, testing, coding thousands of line etc (In addition to my full time work) – I also had to order every component from of-shore for my experiment. As I do not sell KIT – there is no return except my own happiness.

If you like my work and wish to use it – you may show your appreciation and support my effort by a small donation. This is completely optional and has no effect on the support I try to provide over email/chat/Github. 73, S21RC

Leave a Reply