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.
Run the installer on your desktop PC (note, this
installer runs on the PC and installs PocketDigi via
ActiveSync to your PocketPC PDA).
Finish the install and start PocketDigi on your PDA.
PocketDigi PSK31 Mode
Using your PocketPC PDA to receive PSK31 with PocketDigi
Launch PocketDigi.
Select
Mode from the Channels menu. Then choose PSK31.
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.
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
Launch PocketDigi.
Select
Mode from the Channels menu. Then choose CW.
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.
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).
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.