YASRI Yet Another Soundcard Rig Interface

I do wonder why anyone would buy a commercial computer to rig interface when they are so easy and cheap to make?

This is the one I use between my computer and IC-746. It works with all the soundcard software I have tried including WSJT, Ham Radio Deluxe, MMSSTV and MMTTY. I claim absolutely no originality for this circuit. There are many other similar examples on the web. I have listed UK Maplin part numbers to help you locate the components. Of course all these components are available much cheaper than Maplin prices of you shop around. Total cost at current (Jan 2013) Maplin prices excluding a metal box is about £33.25

Please note that you build this at your own risk. I cannot be responsible for blown up rigs. If you don't know what you are doing then please buy a commercial interface. In particular be careful not to short out the supply pin on the microphone connector of your rig! Damage may result.

Construction notes.

The interface should be built into a metal box for screening. Construction can be on a small piece of Veroboard, or the components can be simply hung ugly style on the sockets.

I used phono sockets for J1 to J6.

NB. J2, J4 and J6 must be insulated from the case to prevent forming a ground loop between the computer and rig. The outers of J1, J3 & J5 are connected to the box and therefore the rig ground.

In practice I built the opto and diode for the PTT into the serial D connector shell (there is plenty of room) in which case J6 does not need to be insulated from ground. RTS is Pin 7 and GND Pin 5 on a DB9 serial port.

S1A/S1B is a DPDT toggle changes over between the computer and the microphone. If you don't mind changing plugs when swapping between SSB and computer modes you can leave out this switch and the 8-pin mic socket.

In the case of my IC-746 the Mic input is Pin 1, the PTT Pin 6 (not Pin 5 as described in the user guide, and the GND is Pin 7. Yaesu rigs are wired differently, please check your manual.

Details of microphone wiring for many rigs can be found on G4WPW's web page.

J1 is the feed to the rig mic input (Pin 1 on the IC-746)

J2 is connected to the computer soundcard output

J3 is the audio feed from the rig on receive

J4 connects to the input to the soundcard

J5 is the rig PTT (Pin 6 on my IC-746)

J6 is connected to the RTS line on the computer serial port for PTT switching

C1 to C6 should be soldered directly onto the back of the socket with short leads
Qty Description

Maplin Part

Price each Subtotal Notes
1 6 X insulated Phono skt JH95D £1.99


J1 to J6

Or use seperate insulated phono sockets (more expensive) or a DIN plug/skt

1 8 pin locking chassis plug (mic connector) FK29G £2.79 £2.79 Use the same type as your rig mic socket this for the IC-746
2 Min audio transformer LT44 £2.29 £4.58 T1 & T2
1 10K LOG FW02C £1.69 £1.69 R1
1 1k MF M1K £0.29 £0.29 R2
6 10nF disc ceramic BX00A £0.39 £2.34 C1 - C6
1 10uF 25V electrolytic AT02C £0.69 £0.69 C7
1 IN4148 QL80B £0.39 £0.39 D1
1 Opto AY44X £0.99 £0.99 If out of stock substitute almost any opto
1 Metal box Choose whatever you like
1 DPTD toggle FH99H £2.29 £2.29 S1
You will also need some plugs and sockets to connect the box to your rig and computer, ( exact details may vary depending on rig model, these are for the Icom IC-746)
1 8 pin line socket FK30H £2.79 £2.79 Mic plug for Icom/Yaesu rig
6 phono plugs HH01B £1.49 £8.94 Metal phono plug-
1 9 way hood KE94C £1.49 £1.49 hood
1 serial plug RK61R £1.99 £1.99 9 pin female

Plus enough screened cable to go between interface and computer and interface and rig.

Total cost to build Jan 2013 (excluding a metal box) £33.25

If you have any questions on any of the above or you just want to tell me that you found it useful or indeed useless then please email me: paulATg4dcv.co.uk 73 Paul G4DCV