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Pocket RTTY PSK CW Using PocketDigi
+ MobileLog + Tigertronics SL-1+

Look ma, no laptop.

Shirt-pocket RTTY and PSK is a reality!

If you're a ham radio operator who is interested in digital modes (RTTY and PSK31) and you have a PocketPC PDA, you really need to take a look at PocketDigi. This Open Source application (thanks to Vojtech, OK1IAK) is a port of the Linux ham radio utilities collection known as gMFSK to the PocketPC platform. By itself, you can hold your PocketPC PDA near a speaker and decode RTTY (teletype), PSK31 and even CW. That's pretty cool - but PocketDigi does more than just decode incoming RTTY, PSK and CW signals, it also encodes them.

One of the tricky parts of setting up a PocketPC PDA for PocketDigi operation is how best to pass audio to and from the ham radio transceiver. I've found the Tigertronics SignaLink SL-1+ to be the ideal solution for interfacing your rig to your PDA and this page describes why, how to setup the system, and your options for interfacing the PDA to the ham radio transceiver.

Once you've cabled your audio lines, you'll need to tweak your PDA audio settings and your audio and mic gain settings on your ham radio transceiver. Then you're ready to start making some QSOs on the bands.


Creating a PocketPC PDA Digital Mode Ham Radio Station

Of course, the first thing you'll want to do beyond just decoding incoming audio is connect it to your radio and take it on an HF backpack adventure. Have you ever wondered about the possibility of using a QRP rig on a mountaintop with a simple portable HF antenna and your PocketPC for a PSK31 QSO?  Then this is definitely for you.

In order to transmit an audio signal from the PDA to the radio, you'll need an interface. There are many PC sound card to radio interface choices from commercially available products to plans to construct your own. Although I have a West Mountain RigBlaster in my ham shack, I decided to order a Tigertronics SignaLink SL-1+ for this task. Several reasons for this choice:

  • Audio PTT: Most radio to soundcard interfaces key your radio using a separate serial line from your PC. One big advantage of the Tigertronics SignaLink interfaces is that they key the radio (PTT) by triggering on the audio levels (similar to VOX).
  • Portability - I needed a unit that could be powered in the field easily. Powering the SL-1+ can be accomplished through the radio's mic jack, data port or accessory port. You can also power the device externally. The SL-1+ accepts 6.75 V to 15 V DC at 10 mA.
  • Convenience - The SignaLink can be connected to the accessories or data jack on the radio. In this setup, I can leave my mic connected.

Setup your PocketPC PDA to use PocketDigi

If you are new to PocketDigi, take a look at the PocketDigi Introduction on this site. My current collection of PocketPC PDAs includes the iPAQ 3630, the iPAQ 2215, and soon the Cingular 8100. PocketDigi should work well on any PocketPC PDA with a reasonably fast CPU (200 MHz or greater) and audio (input and output).


Getting audio from the ham radio rig to the PDA

Once you have the Tigertronics SignaLink unit, getting your transmit audio from the PDA to the ham radio transceiver is easy. The tricky part is passing the receive audio from the rig to the PDA for demodulation. Why? Very few PocketPCs have a mic jack! So, what are the options for getting audio from the rig to the PDA?

 You can also build your own adapter cable for these PDAs using instructions found here.

  • Hack the PocketPC
    If you're brave, not afraid to deal with surface-mount components, and know which end of the soldering iron is hot, you might take this route. Of course, any damage you to do the device is on your hands, not mine. If you're willing, you might search the net for a hack to add an external mic to your PocketPC such as this page to add one to a iPAQ 3650.


  • Hack a wireless headset (for example, Bluetooth)
    Wireless headsets are fairly common and relatively inexpensive.


Configure the Tigertronics SignaLink SL-1+ for use with the PocketPC PDA

Tigertronics has a thorough installation manual for the SL-1+ that covers everything from setting the jumpers for various radios to adjusting transmit audio. Some key points that are often overlooked by those new to sound card digital mode operations:

  • Don't forget to turn off your radio's speech compression. Speech compression can lead to terribly distorted signals and you'll likely get complaints about your signal on PSK or RTTY.
  • You'll need to set the audio levels of the PocketPC to the "Goldilocks level" (not too hot, not too cold... just right). The rule of thumb of finding the absolute minimum level to trip the PTT, then going up about 50% above that is probably ok.
  • If you have anything on your PocketPC that generates unexpected noise, disable it first. Meeting reminders, ActiveSync sounds, etc. all are sent out of the audio jack and, of course, are passed by the SL-1+ to the rig. The last thing you want to do is broadcast (illegal) junk from your PDA.

Logging Ham Radio Contacts on your PocketPC with MobileLog

Don't forget to log your QSOs! MobileLog is the best way to record your ham radio QSOs on your PocketPC PDA. Check it out.