Configuring fldigi via RIGblaster Plug & Play to an ICOM IC-718

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Fldigi setup - click to see larger and detailed notes on components
IC-718, Rigblaster, and fldigi
Click for larger version with detailed notes on components

Hams have known for a century how much fun it is to use narrowband digital communications to punch through atmospheric conditions and make a little power communicate over very long distances, sometimes literally around the world. One of the fun ways to do this today, especially for newly minted hams without International Morse code skills, is to use a computer to modulate the signal and do the decoding for you.

What is fldigi?

One of the best programs out there for computer modulation is fldigi. It is free, open source software. Ultimately it does a lot of what Internet chat does, but you can do it on battery power, and without an Internet, or wires. Fldigi visualizes the signals across the audio frequency space over time using a colorful waterfall display. It has a built in software modem to transmit and recieve audio using your computer's sound card. It has several ways it can assert a push-to-talk (PTT) signal to cue your transmitter. If your transceiver supports a data connection it can also communicate frequency settings between fldigi's screen and your radio.

With all these neat features, the configuration of fldigi can be confusing. This article came about because I have figured out the settings for the last time - I want to park my notes where I can find them again, and share them with you, dear reader.

Hardware and Software Basics

There is a whole plethora of hardware available for hooking serial, USB, and sound card audio up between your PC and your radio. I've played with a Signalink USB with its built-in soundcard, but today I'll focus on configuring a West Mountain Radio RIGblaster Data Jack plug and play, to work with fldigi on Linux, to an ICOM IC-718.

First off, make sure your sound card works correctly with Linux. I'm using a software distribution, Fedora 13, based on the Gnome project and pulseaudio. Right click on the little speaker in the upper right corner of the gnome panel, and select Sound Preferences. This will start up the gnome volume control applet.

Hook up the RIGblaster Plug & Play

Now hook up the cables per manufacturer's directions. Special notes:

Turn on your IC-718 and tune to where the warbling sounds of PSK31 signals may be heard. This morning, setting the mode to USB and tuning to 14.070.00 is yielding a great signal. Note your AF gain setting is for your ears' pleasure alone - the data jack provides an audio signal that is constant gain.

Install fldigi and Configure Audio Input

Install the fldigi program. It's in most package repositories for standard distributions, so select it from your package manager graphical tool and install it, or for example on OpenSuSE type 'zypper install fldigi' or on Fedora 'yum install fldigi'.

Start up fldigi.

The waterfall should start displaying signals as yellow streams flowing down the display with red centers, on a blue background. If you don't see this, then

Configure Push-to-talk (PTT) and Hamlib

Hook up your IC-718 now to a dummy load - we are about to test things that touch PTT and Transmit.

Head back to fldigi. In the main screen click through Configure -> Rig Control...

To confirm success, the frequency display in the main display of fldigi will now track any changes you make to the frequency knob on the transceiver.

If you had any problem with that, make sure your CI-V cable is installed correctly (see above) and make sure your IC-718 is set to the default CI-V configuration:

Configure Audio Output

Now we know we are getting input and rig control is working, so it's time to work on the output path.

Any problems at this point are in the Rig setup in fldigi, so head back there to debug.

Transmit Settings, into a Dummy Load

Now PTT and PC speaker out are working, we're ready to modulate the audio going into the transceiver.

After following all the above steps, you now have input audio correctly adjusted, rig control, PTT working, and modulation out of your PC correctly adjusted for producing clean PSK31 signals at maximum power.

Tuning up with your Transmatch

Next we'll tune up on the real antenna.

Et Voila!

Now you are all set up for using fldigi on Linux through a RIGblaster Plug and Play to your IC-718.

After writing up these instructions I sent a CQ and was hit right back from a nearby neighbor, and we logged a delightful contact.

Good luck! You can reach me at kn1x (at) if you have any questions. Feel free to browse my general ham radio page or my personal home page.