de WAØTTN - PSK31 on PDA Devices
I've received a number of requests to port the WinPSKX ActiveX control
to operate on PDA (Personal Digital Assistant) devices,
most notably the Compac iPAQ, aka the Pocket PC, running the WinCE "operating system". Since WinCE is
the closest relative to the Windows environment, I'll discuss PDA in relation to it.
While WinCE devices appear to be miniature versions of personal computers
running the Microsoft Windows operating system, they are quite different. This article explains the
limitations of these devices.
Intended Usage
WinCE devices appear to perform quite remarkably for their size, however they have quite limited resources.
These devices work best in a wireless network environment and can be thought of serving a purpose similar
to the remote head of your tranceiver. Their primary purpose is to provide an interface to the user, and
provide a communications channel between the user and the resources on the local area network (LAN).
They do have a notable degree of processing power on their own, and can be used to some extent in an
offline manner. However, the intended purpose is to provide a highly-portable user interface device,
as opposed to a full-blown, semi-portable computer system such as a laptop.
The illusion that the WinCE devices are miniature personal computers has sparked the idea,
numerous times, that these devices might serve as a PSK31 terminal.
Floating Point Processor
By far, the most limiting factor is the lack of a floating point processor (FPU). The DSP
computations for encoding and decoding the PSK31 data, and the FFT computations for performing the spectral
analysis, are quite math intensive. Some of you may remember how personal computers performed back
in the days of the 80386, the processor of the venerable first-generation personal computers.
Intel developed the 80387 math coprocessor
to answer the demands of the computationally challenged 80386, but it was the 80486 with its embedded
FPU that really got us on the road to high-powered number crunching. I only point this out to remind
us all that FPUs were once, and in the case of the handheld devices, considered a luxury, not a given.
Like the original personal computers in the days of yore, most (if not all - I need to do more research)
WinCE devices do not incorporate an FPU.
The intent, as mentioned previously, of the WinCE device is to provide a user interface. While there
is a floating point emulation library available, the computations required for the PSK31 processing
are not be feasible.
Microphone Input
Most (if not all - again, more research required) WinCE devices provide an earphone jack for private listening.
This can easily be used for the PSK31 encoder output.
However, the WinCE devices typically do not provide an input jack, but rather
only a built-in microphone. While it is possible to simply tape a tranducer, such as a small speaker or
earphone, over the WinCE device's microphone, audio quality and ambient noise may present a problem
for PSK31 decoding.
Other Issues
Although not an insurmountable issue, the lack of a keyboard means that PSK31 transmission must
rely heavily on macros. In the occasional case where the user absolutely must resort to keyboard input,
the Pen gesture interpreter and/or keyboard emulator would suffice,
although not as effectively as a standard keyboard.
As will be discussed further below, PDAs do not have many options for data exchange either. In the
typical environment, a PDA uses a wireless network for data exchange while roaming.
For stationary use, a cradle typically provides a USB connection to a desktop computer.
Some Possibilities
One option I've considered for using my iPAQ around the house as a remote PSK31 device is to port the
Network WinPSKX experiment to it. The iPAQ would serve as the host for the
remote PSK31 application client, while the heavy DSP and FFT number crunching, and the soundcard interface
to the radio, is handled by a desktop server over the network. This is certainly feasible. But as I've
suggested in the Network WinPSKX discussion, is it really useful?
Naturally, the desire for a truly portable handheld PSK31 device, capable of performing the DSP and FFT
computations, is great. A couple of other options show promise also.
One suggestion Moe Wheatley, AE4JY, has made is the possibly of using an SDR
(Software Defined Radio), such as Bob Larkin's DSP-10:
http://www.proaxis.com/~boblark/dsp10.htm.
In this case, the SDR provides the radio transceiver and PSK31 encoder/decoder functionality, and the
PDA would simply provide the user interface. The hardware interface between the SDR and the PDA is
yet another consideration, and is discussed further below.
Another possibility comes from the New Jersey QRP club's self-contained PSK transceiver.
http://www.njqrp.org/portablepsk/index.html
In this case, the Motorola DSP controller board has been programmed for PSK31 encoding and decoding.
Unfortunately, handheld devices don't (as far as I know) have serial I/O ports, so another means of
interfacing the hardware would need to be employed.
In both of the previous two possibilities, the hardware interface between the PDA and the hardware is
an issue. There are two sets of data required, the text data representing the QSO, and the spectrum
data for the waterfall display. In order to achieve sufficient throughput for the spectrum data, a
USB connection is likely the only feasible solution.
However, the device must usually be resting in a cradle which provides the USB connector. So, again,
it's not a truely mobile configuration.
Conclusion
This does not mean that there is no hope for a truely portable PSK31 device. The intended purpose
and use of the current PDA technology is just not sufficient for PSK31 at this time. The lack
of a floating point processing means that an external device must handle the PSK31 encoding and decoding.
And the hardware for data exchange limits how the PDA might be connected to an external DSP device.
But time will tell. Technology marches on, and we PSK31 die-hards will continue to search for
a truly portable PSK31 solution.
73 to all,
Dave Cook, WAØTTN
Send e-mail to Dave: 
Go to the WAØTTN Web page.
Go to the Dave Cook Consulting Web page.
Last updated March 21, 2002