Make a low cost sound card for data modes

Sound cards for data modes don't have to be expensive

Data mode communication can be easy and fun, low cost rigs like uBitx and the Xiegu G1M are perfect for data mode communication. One issue maybe that commercial Ham radio sound cards can be expensive. Why? Well they usually include group loop isolation (which is important), they also often include knobs and dials (which are not really important).

It doesn't have to be this way. A cheap $5 USB sound card combined a $10 USB isolator will perform just as well.

On this page I'll show you how to make a basic data mode sound card the low cost way, with no compromise on performance.

Low cost sound card for data modes
Data mode sound card

Low cost sound card shopping list

In this guide the following items are used:

  • USB External Stereo Sound Adapter - Internet shopping site
  • USB isolator - Internet shopping list
  • 3.5mm jack plug leads, male x 2 (stereo) 

Optional software:

Why use the USB isolator? What are ground loops?

Without a method to electrically isolate the audio signals between the radio and the PC, it's very likely that there will be excessive electrical noise transposed on to your audio signal. This can look like noise, or regular wavy lines. The cause of this type of noise is often referred to as a 'ground loop'.

This type of noise will significantly reduce your ability to decode signals, and will also impact your transmitted signal.

The USB isolator we use here will electrically isolate the sound card and eliminate those ground loops, improving your ability to decode and send data mode messages.

How to connect the sound card to a radio for data modes

Connecting the sound card up is quite straightforward. If you get stuck just stop and think about what is being connected to what.

Note: Ensure your CAT control is set up and working before starting.

Sound car assembly

1) The USB sound-card plugs directly into the USB isolator, this assembly plugs into your PC or Raspberry Pi 

Audio cables

2) The Green jack socket of the sound card connects to the Microphone I/P of your radio. This will provide the audio signal sent from your PC to the radio

3) The Red jack socket of the sound card connects directly to the audio O/P of your radio. This provides the audio from you radio to your PC

CAT control

4) Connect your regular CAT lead to your radio in the normal way, this will be used to Key your radio and set the frequency.

 

Xiegu G1M and Raspberry Pi working data modes
Xiegu G1M and Raspberry Pi working data modes

Data mode software settings

Fldigi is a good software package for the Pi, Ham Radio Deluxe is good for the PC.

Audio settings

Configure your favourite data mode software to talk and listen through your USB sound card. These things will usually be configured under the Audio menu, under Settings.

Left channel only!

Configure your software to send audio through the left channel only. This is the tip of the jack plug, this is usually configurable under the software settings.

PTT via CAT

Make sure you can key the radio via CAT, VOX will not work. So you need to get this working correctly for this to work.

Set audio levels

Set the sound levels using the relevant sound control sliders for your operation system.

Windows PC

If you are using a Windows PC I recommend using 'Power mixer' as this makes things easier.

Raspberry Pi

On a raspberry PI just hit the Audio setting button in the top right hand corner.

Tx output levels: Transmit in to a dummy load, look at your ALC level on your radio. Set the PC audio output level so that the audio level just touches the ALC bar (usually the middle of the ALC scale)

Rx input levels: Look at your data mode software audio bar, using both your PC Mic level and Radio volume knob, set the level appropriately.


This is a great low cost sound card solution for data modes

I am very happy with the performance of this simple, and low cost sound card. The USB isolator adds the magic by eliminating the ground loops. The Power mixer software makes understanding the sound card arrangement and setting the levels easy.

A great low cost sound card solution for all.

Setting up the Yaesu FT-817 for data mode communication
Setting up the Yaesu FT-817 for data mode communication

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