MultiMode is an application which allows your Macintosh to decode several different modes of non-voice communication often heard on shortwave. You can also transmit in many of these modes, as well. In the past, dedicated hardware, often costing hundreds or thousands of dollars, was necessary to demodulate and decode these transmissions. Today, you can use the processing power of your Macintosh to decode and display these modes, without any hardware.
MultiMode features sophisticated digital filters, for pulling weak signals out of the noise. MultiMode OSX requires a Macintosh running Mac OS X 10.5 or later. If you are running an older version of Mac OS X, please visit the download page to see what versions may be available for your system Please feel free to download a copy prior to purchase, and see how it works on your system.
You also need a radio capable of tuning in the frequency ranges of interest. If you want to transmit, you’ll need a transceiver of course. For most modes, this is a shortwave radio. For ACARS mode, a common VHF band scanner is used. The audio from your radio (speaker or headphone jack) is fed into your Mac’s sound input port, through an appropriate cable. The radio is tuned to the station, and the correct mode is selected. MultiMode has a feature which displays the audio spectrum of the station, as a tuning aid.
For transmitting, you simply connect the audio output of your Mac to the microphone input of your transmitter, possibly through an isolation transformer. There are many devices on the market that can do this for you, or you can do it yourself.