Radio/PC Interfaces: Everything You Need to Know

There are many brands of interface available to connect a PC to a ham radio transceiver. Often home-brew interfaces are used. They all do essentially the same thing.

They key the radio to transmit, pass a signal based on the mode of operation from the PC to the radio, then un-key to go back into receive mode.

Some automatically bypass the microphone

Sites about soundcard interfacing


  • Digimaster from ZLP Electronics. A variety of interfaces and connecting cables are available.
  • PCInterfaces In both kit and pre-constructed form.
  • Microkeyer USB interface from Microham. Other models are available.
  • SignaLink from Tigertronics. Two models available, one that used the computer soundcard and DB9 connection, the second has a built in soundcard and connects via USB
  • Rascal GLX from Bux CommCo. Available in kit or constructed form. A variety of cable options are also available from the site.
  • Rigblaster from West Mountain Radio. Has interface models with both USB and RS232 DB9 connections. Includes inbuilt rig control capability.
  • RigExpert USB interfaces and MixW software.
  • VA3TO linking interface. Operates under EchoLink software and doubles as a soundcard interface for various digital modes.

Home Brewing

Interfaces can be fairly simple and thus are easily home-brewed. Here are 2 schematics. The first one is for PCs with a serial port being used for PTT, the second one for an Asus Eee netbook. It uses a VOX circuit for PTT.

Tips for using interfaces

Using the signaling USB with and ACER Aspire ONE for WSPR and MMSSTV / MMVARI File:Signalink.pdf

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2 thoughts on “Radio/PC Interfaces: Everything You Need to Know”

  1. One thing to note, is tablets, pads and smart phones do funny things with their mic inputs.

    1, DC bias out for electrets
    2, Resistance values for function buttons like volume control on ear buds and the like.

    Therefore you can not just put an audio transformer across the mic input things will go wrong. Likewise you can not just have a level shifting pot as that will put DC resistance that looks like switch operation.

    Look up CTIA 4 pole jack (TRRS 3.5mm) interface for more info on Android and the four buttons it alows and OMTP interfaces that are required by legislation in some jurisdictions.


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