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?
- Place the PDA
near the XCVR speaker
This is the
the low-tech approach. I've found that if I have a
relatively quiet area I can position my PDA near the
radio speaker and it will be able to copy "gud enuf"
with a decent (RST=599) incoming RTTY or PSK31
signal. Of course, it gets a bit frustrating when
you start missing characters and guessing at words
and such, so I started investigating other
alternatives. In this scenario, you'll likely be
using VOX to trigger the PTT on the transceiver.
- Check the PDA specs.
Maybe you already have a mic jack and don't know it.
As I said, there are few PocketPCs that have a
built-in mic jack. Most PDAs have a built-in mic
(with a pin-hole for picking up the audio when
recording) and no other means of getting audio into
the device. However, a few PocketPCs have a
dual-purpose headphone jack that can accept a mic.
These units typically have a four conductor 3.5mm
jack. With an adapter from PocketPCTechs you should
be able to split the audio out and in lines. This is
well worth looking into if your PDA is one of the
following:
| HP iPAQ |
T-Mobile |
iMATE |
HTC |
Qtek |
Dopod |
O2 |
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| Palm |
Sony |
Audiovox |
AT&T |
Orange |
Cingular |
Siemens |
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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.
