Note: This article is quite old now, however I'm leaving it here for reference. In the intervening years since I wrote this, mobile processors still do not support hardware floating point, or at least not to any extent. However, there is at least one PSK31 implementation that does run on a the Windows Mobile operating system, PocketDigi written by Vojtech Bubnik, OK1IAK. Vojtech's excellent solution was to us a fixed point math library. While fixed point computation in software is effective only up to a certain point, this program works very well on modern mobile devices with sufficient horsepower.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.
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.
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.
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.
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
Go to the WAØTTN Web page.
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Last updated May 31, 2010