More Linux & Radio

Day two of my field-testing the Linux netbook. The machine I use is an Asus eeePC Seashell netbook with an Intel Atom 1.5GHz processor and 2GB RAM. It will last ~8 hours on a charge and is plenty powerful enough to multi-decode in Fldigi.

eeePC Linux ham radio computer

eeePC Linux ham radio computer

Yesterday I was successful in sending out APRS beacons using the Linux soundmodem AX.25 (TNC alternative) driver. The soundmodem driver uses a computer sound card as the modem (modulator / demodulator) by performing some digital signal processing on the audio data. Thus, to use packet radio (and therefore APRS) all that is needed is a radio, a sound card (with interface cable) and a computer. No need for a TNC!

Garmin GPSMAP 62S

Garmin GPSMAP 62S

Yesterday evening, I played around with my Garmin 62S and gpsd – a Linux gps server daemon which allows multiple simultaneous logical connections to a GPSr.

As an aside, a close friend of mine might remember something I once muttered while first playing around with (ie. learning) Linux back in 1995:

“What the hell is a server daemon? … and what the hell are daemons doing in my computer?”

Garmin 62S setup help

Garmin 62S setup help

I had mucked around with /dev/ttyUSB0 (my GPSr’s logical device) for some time yesterday, trying to get gpsd and xastir playing nice together – no luck. Well, a fresh set of eyes later in the evening proved helpful as I managed to get the GPSr talking nicely with gpsd. The stumbling point? Getting the GPSr to output data in real-time over the USB connection. How did I manage it? Garmin Spanner format (with mass storage disabled).

garmin GPSr -> setup -> system -> interface -> Garmin Spanner
USB cable detected. Would you like to go to Mass Storage? -> NO!

With the above change in place, I restarted the gpsd daemon and tested the output using a command-line tool called cgps:

$ sudo gpsd /dev/ttyUSB0
$ cgps
xastir configuration hints

xastir configuration hints

Success! The gpsd server was now seeing packets from the GPSr which meant I could now pipe that data into xastir (the Linux APRS client I use) via an interface setting. With xastir now querying the gpsd server, my current coordinates were properly being reported in real-time and thus, my APRS station was set up.

Next on the docket was getting pskmail up and running. My objective was to connect to a pskmail server and send a test email to myself to verify correct configuration.

I fired up Fldigi, followed by pskmail 1.5.7 (the order of operations matters as pskmail is not smart enough to check that Fldigi is running first – it simply throws a lame error message). I tuned my radio to 10.147MHz (USB) and listened for a few minutes for some pskmail server announcements. Lo and behold, a PSK250R signal appeared at 1000Hz on the waterfall which corresponds to 10.148MHz (the center frequency for pskmail).

The server announced itself as KB2PNM (North Carolina) and so I added that callsign to my server connection list in pskmail. Once the station was added, I clicked on connect and sure enough I was in business!

I poked around pskmail a bit and managed to discover how to send an email so I fired off a few test messages to see how well the system works. I have to say, it was pretty darn quick all things considered!

What is neat is that pskmail can also use gpsd to obtain your current coordinates and send your APRS data via HF to a listening igate. I took the opportunity to update my VE3BUX position via HF and the reporting station is listed as KB2PNM (as should be expected).

This looks like a pretty robust HF communications suite! I’ll have to play around a bit more to really learn the ins-and-outs and I will certainly post my experiences on here.

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