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PocketDigi - Ham Radio Digital Modes for the PocketPC   

What is PocketDigi?

 

PocketDigi is an open source utility developed by OK1IAK to provide ham radio operators with PocketPC PDAs with the ability to use (encode and decode) digital modes such as RTTY (teletype), PSK (phase shift keying), and CW (Morse Code). 

Want to take your PocketPC PDA to go backpack mobile and work PSK31 QRP? Then, PocketDigi is the app for you! Since the advent of mobile computing, radio amateurs have been exploring creative ways to utilize laptop computers and PDAs for portable ham radio operations and mini-DXpeditions.

PocketDigi was created by Vojtech OK1IAK who built the utility using Microsoft's Embedded Visual C. He used (and improved) portions of a Linux GNU open source application called gMFSK to do encoding and decoding.

Currently, PocketDigi is still in early development stages and has not been fully tested on every PocketPC platform. However, many hams have reported good results on PocketPC PDAs using at least a 206 MHz processor.

Fortunately, Vojtech has made PocketDigi freely available, along with source code, via the SourceForge website. This will undoubtedly lead to future development and improvement of this application for the ham community.

Installing PocketDigi on your PocketPC PDA

Installation of PocketDigi is very easy.

  1. Download the PocketDigi installer.
  2. Run the installer on your desktop PC (note, this installer runs on the PC and installs PocketDigi via ActiveSync to your PocketPC PDA).
  3. Finish the install and start PocketDigi on your PDA. 

 

PocketDigi PSK31 Mode

Using your PocketPC PDA to receive PSK31 with PocketDigi

  1. Launch PocketDigi.
  2. Select Mode from the Channels menu. Then choose PSK31.
  3. Position the PDA near the radio speaker such that the PocketPC's built-in microphone will pickup audio from the radio. Make sure that the audio level is plenty strong. The waterfall audio display at the top should show the incoming signals.
  4. Next, select an incoming audio stream by clicking on it in the waterfall display. It should look something like this:

 

 

 

 

 

At this point, the PDA should be receiving PSK31 text (or at least gibberish) in the output box. If it's mostly garbled text, you'll need to tweak.  The first thing to try, is to make sure that your cursor (arrow) is exactly centered on the signal.

Other options:

FFT selection. FFT, or Fast Fourier Transforms, are computer algorithms which are used to convert the signals into text. Choosing a different FFT setting will rescale the PocketDigi waterfall graph at the top. This might help you center your cursor on the PSK signal. 

AFC or Automatic Frequency Control will center the cursor on the strongest signal, automatically.

 

Using your PocketPC PDA to send PSK31 with PocketDigi

To send PSK31 text, choose Send from the Tools menu. You should hear PSK31 audio coming from the PocketPC speaker or headphone jack. Begin typing. When finished, choose Tools -> TX stop to end your transmission. The current version does not offer macros.

If you would like to have a "brag file" (canned text to be sent all at once), you can simply store that in a text file on your PDA.

 

PocketDigi CW Mode

With PocketDigi, you can decode Morse Code using your PocketPC PDA. No, it won't flawlessly copy RST=339 60 wpm left-footed CW with heavy QSB sent with the syncopation of jazz drummer. But for those who are learning Morse Code or who have some hearing loss, PocketDigi offers a fun way to get in the action on the ham radio bands.   

 

Using your PocketPC PDA to receive CW (Morse Code) with PocketDigi

  1. Launch PocketDigi.
  2. Select Mode from the Channels menu. Then choose CW.
  3. Position the PDA near the radio speaker such that the PocketPC's built-in microphone will pickup audio from the radio. Make sure that the audio level is plenty strong. The waterfall audio display at the top should show the incoming signals.
  4. Select the Max RX speed. This is the an approximation of how fast you think the CW is being sent at its fastest speed. By setting this value, you are giving the decoding algorithm a clue about the incoming audio (a "dah" at 60 wpm CW might be shorter than a "dit" at 5 wpm).
  5. Set the filter. To do this, choose Filter BW from the Channels menu and select a bandwidth. This step will help the DSP software within PocketDigi narrow in on a particular Morse Code signal.  If you have multiple hardware or software filters in your transceiver, you'll know the impact of this step. Setting a filter too narrow on a fast CW signal causes problems. Setting the filter too wide under noisy conditions (QRM) is also a problem for the decoder.

Interpreting the results - 20 wpm CW

Here is some Morse Code that has been "decoded". To run this experiment, I played the audio output (using Morse Runner) from my laptop PC into my iPAQ 2215 PocketPC. In the receive box, you'll see some text that might look like gibberish. If you sort of squint, you can see the PDA decoding my CQ string (CQ TEST DE N0HR TEST). In one QSO, I gave WB2JEP a 5NN TT1 (contesters will recognize this as a CW RST of 599 and a report of 001).   Then you see some junk (noise that the PocketDigi program attempted to decode). Next there is another CQ and a QSO with N6PZ (I sent a 5NNTT2).

The moral of the story is that yes, it can decode CW, but you'll probably only want to use it as a backup to the decoder between your ears.