fully analogue AM/FM ($10): tuning performed by knob rather than buttons. Current frequency indicated by physical movement of bar, dial or similar. Their technology hasn't changed much since the first transistor radios arrived in the 1950s.
slightly digital AM/FM ($20) - again tuning performed by knob rather than buttons, but with frequency indicated by digital display. Stations can't be stored, and frequency can drift with temperature, time and orientation. Mine [see top photo, zoom in for closer look], a Digitech AR1740 from Jaycar, was described as "Radio Receiver AM/FM/SW with LCD and Clock. This multi-band pocket radio has digital scanning and has a large backlit LCD." They've tried to hide its lack of digital functionality by including clock and alarm buttons obtrusively on the front of the radio. What looks like a huge jog dial is actually the hours and minutes setting buttons. The tuning is all done by a dial on the right-hand side.
- fully digital AM/FM ($30) - as digital as analogue radio can be. Tuning is done by the press of a button, and once a signal is found it is maintained through the use of a phase-locked loop. Favourite stations can be stored. Most car radios are of this type now, but pocket radios are still not that common (in Australia at least). Aside from the outrageously expensive ones (ie. anything over $70) TEAC make the PR63 being sold in JB Hi-fi for $30. I haven't tried it, but the specs look promising.
Finally, we come to true digital radio. No longer AM/FM, this is a digital signal that requires a whole new radio. Listeners in Australian capital cities can expect to hear DAB+ in January 2009, though as of yet there are no consumer DAB+ receivers available to purchase. Other countries have been using an earlier standard, DAB, for a number of years, and users seem happy. However, due to the low bit rates that stations generally transmit in the quality has not been an improvement on FM. DAB+ promises better quality at lower bit rates.
Is a "slightly digital" radio any good?
When I started to use my new radio I was wondering if it would prove a useful improvement over a fully analogue one. I'm happy to report that it certainly is. The highly-accurate digital display of frequency makes tuning into stations noticeably easier, and tuning into marginal stations no longer a hit-or-miss affair. Fully digital would be better, but for the price the "slightly digital" is great. This model consumes two AA batteries, which I prefer over the AAA's of smaller models. It describes itself as multiband, which means that it stretches into shortwave as well as medium wave and FM. However, of the 7 SW ranges offered (chosen from the top switch) 2 are permanently stuck on a single frequency, so there are some frequencies I can't reach. However, that's not a loss for me, as without a 10m aerial there isn't much to listen to on shortwave in Perth.
One question I have is why FM tuners are so common in mobile phones and MP3 players, but none have AM tuners. Most of my listening is of AM, so I am stuck with single-function radios. I don't have an active mobile phone, but I'd certainly consider buying a new one if it came with an AM tuner.
(CC-licenced pictures from Roadsidepictures, johnmuk and me!)
Update 25-Apr-2008: The Sydney Morning Herald describes in detail the exciting new world of digital radio in Australia.