Interfacing Your Macintosh To Your Transceiver To Run MultiMode

What You Need

For starters, a copy of MultiMode of course!

If you only want to receive, that is, not transmit, you just need a suitable radio receiver. For most modes, this would be an HF (shortwave) receiver. Some of the modes, such as ACARS, require a VHF receiver (scanner).

If you want to transmit as well, you of course need an amateur transceiver.

Connecting Your Mac To Your Radio

If you want to receive only, you don't need a serial port on your computer. You do need a sound input jack, often called a microphone or line in jack. Most Mac models have these, but some do not. If your Mac doesn't have sound input, you can use a Griffin iMic or other USB sound input device.

Just feed the audio from your receiver into the microphone or line-in input of the computer. Some receivers have a line out jack. Often this is a 1/8" mono jack. A simple audio cable with 1/8" plugs on each end from Radio Shack or the local Radio/TV store will usually work.

If you want to transmit, you have a few options. You need to get the audio output of your Mac into your radio. You can build a cable that takes the speaker output and runs it into the microphone jack or other input jack on your transceiver. You can also buy a RigBlaster or other such device which has all the necessary cabling. We have also heard good things about the SignaLink SL-1 plus from Tigertronics.

You don't need a RigBlaster to use MultiMode, but it can make the connections much easier to do. As there are too many different radios out there, we can't give you specific information on how to connect to a particular model.

To control the PTT on your transceiver, you have two options. You can use a RigBlaster which can do this for you, it senses when there is audio coming out of the computer and switches PTT. Or you can use a serial port on your computer, and build an interface that switches PTT on your radio, using an opto-osolator, relay, etc. You would need to investigate how to do this on your particular radio.

MultiMode can assert the DTR and RTS handshake lines from a serial port, which you can then use to control the PTT and CW key lines on your radio. You will need to build the appropriate cables, as well as any circuitry necessary for voltage level shifting, isolating etc.

The only use for the serial port with MultiMode is to control PTT on the radio, it does nothing else. So if your Mac doesn't have a serial port, and you want to transmit, a RigBlaster may be the best way to go.

MultiMode - Decodes weather fax and satellite images on your Macintosh, without the need for extra hardware.

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Chris Smolinski, N3JLY