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Review: Bush TR82DAB DAB+/FM/AM/LW radio By LEO SIMPSON Elsewhere in this issue we have a Vintage Radio article on the restoration of a Bush TR82C transistor portable radio which was introduced in the early 1960s. It became a highly-regarded classic and several reproductions have been made over the decades. Now there is the Bush TR82DAB which looks virtually identical to the 1959 original by Ogle Design but now incorporates modern circuitry with FM and DAB+ reception. 28  Silicon Chip siliconchip.com.au . . . classic 1960s styling, modern DAB+ circuitry I PURCHASED this radio for my wife for use in the kitchen. Since then, it has been universally admired by all our visitors as a ‘retro’ radio which looks really ‘cool’. Little do they know that this radio has long been regarded as a classic. It looks as though some of the original moulds may have been used for the exterior of the case, at least, but the internals are quite different, as can be seen by comparing the photos in this article with those in the Vintage Radio column in this issue. The original Bush TR82C only featured AM reception on the broadcast (MW or medium wave) and LW (long wave) bands. This TR82DAB model is the only DAB+ radio available in Australia which features AM as well as FM stereo reception (NB: the Marantz NA7004 Network Audio Player, as reviewed in the January 2013 issue, also has AM/FM/DAB+ but it is a far more expensive hifi program source. The TR82DAB is also one of the few DAB+ radios which can be powered dirtectly from the mains supply (ie, no plugpack) as well as an internal battery pack consisting of six C cells to provide 9V DC. The virtue of having AM & FM reception is that you can take the Bush radio on a trip or a picnic where DAB+ reception is not available and still be able to get most of the radio programs that you prefer to listen to. Having said that, most people who do not possess a DAB+ radio do not realise that many more stations are available than the sum of all the AM and FM stations broadcasting in a particular city. For example, DAB+ includes the digital radio stations from the ABC and SBS networks which can be received on most digital TVs and set-top boxes. This radio is much larger than many DAB+ radios on the market, with overall dimensions of 335mm wide, 270mm high (including the handle) siliconchip.com.au The dial-scale on the TR82DAB is a replica of the original TR82C design, with European station markings. A modern digital readout (LCD) on the top of the set shows the band selected, the tuned frequency and the signal strength, plus other useful information. and about 90mm deep. With batteries installed it weighs about 2.3kg, so it is not a lightweight. For tuning the FM, AM and LW bands, there is a hand-span dial which is reasonably straightforward to use because it does have reduction gearing. All the other controls are in a recessed panel at the top of the cabinet, underneath the handle which looks as though it is supposed to retract onto the case, but it doesn’t. There are two thumbwheel knobs for volume and tone and the volume knob also doubles as the on/off control. Four pushbuttons select MW (AM), LW, FM or DAB+ operation. The DAB+ station information is displayed in a small LCD panel which is backlit in blue for about 20 seconds after one of the associated 12 buttons has been pushed. After that, the back light goes out but you can still read the information provided you are in a well-lit room. The 12 buttons are labelled auto, menu, display, shift, select, > and <, while the rest are station presets. Ten DAB+ stations can be stored, to be retrieved at the push of the relevant preset button or two. When a DAB station is being received, you can push the display button to show the station information such as frequency, bit rate and signal error. All these functions work quite well and are reasonably intuitive. On the rear panel is a socket for the 2-pin mains cord which must be unplugged from the radio if you want to operate from the internal batteries. Other than that, there is a centrally mounted screw which can be removed so that the whole rear panel can be slid down to reveal the battery compartment. Batteries You might note that I have fitted the set with standard carbon-zinc C cells, although alkaline cells would no doubt give far superior life. Battery life is important because I found that after not many hours of use, the radio would operate satisfactorily on FM or AM but refused to work on DAB+. So clearly it needs a fresh battery pack to work well. It would have been preferable to be able to fit rechargeable cells to the radio but unfortunately, they would have to be removed for recharging. Since the radio has an internal mains transformer and DC supply, it would seem that the designers could have easily provided for the option of automatically recharging the cells. So why not? Once the radio is out of warranty, it would be tempting to make up a rechargeable battery pack with sub-C NiMH cells and with trickle charging from the internal supply when mains power is available. The radio’s on/off switch only operates in the low-voltage DC supply rail so the mains transformer is permanently powered while ever it is plugged in and switched on at the wall. Standby September 2013  29 The rear of the case (left) carries a 2-pin mains socket and a telescopic whip antenna for listening to DAB+ and FM broadcasts. Undoing the large central screw allows the rear cover to be removed to access the battery compartment. power consumption is less than one watt; about 880 milliwatts. When operating normally, power consumption from the 230VAC supply is typically around 4W or 5W, ranging up to over 7W when you have it really blaring. Running from batteries (giving 9V DC), the current drain when in AM or FM mode is typically around 50-60 milliamps but when switched over to DAB+, the current rises to between 240mA and over 400mA when the volume is turned up. With that level of power consumption, it is fairly evident that the battery life will be relatively short. Inside workings Having removed the rear panel, you will find that nothing is revealed of the radio’s internal workings. To reveal that, you need to remove umpteen deeply recessed screws and the front-mounted dial. Naturally, I could not resist the temptation to do so (after all, I wanted a photo or two) but it is not easy to reassemble it. Be warned; unless you need to gain access, leave it well alone. Anyway, inside the set is a large PCB with lots of surface-mount devices. I could see the ferrite rod, the dial cord arrangement and some of the other details but I chickened out at the suggestion that I remove the PCB assembly 30  Silicon Chip to get more photos. After all, I needed to return the radio to my wife in good operating condition and with no signs that any meddling had occurred! The radio has a whip antenna which needs to be vertical and extended to its full length of 580mm for best reception on DAB+ which has vertically polarised transmissions at just over 200MHz. But this length is nowhere near optimum for best reception on FM transmissions which range from 88-108MHz. This means that FM reception may not be quite as noise-free as it might be if it had a longer whip antenna. In metropolitan areas, that probably won’t matter. For AM (MW & LW) reception, the Bush radio has a ferrite-rod antenna which appears to give good reception of both local and more distant stations. Sound quality What about the sound quality? I have already commented in the past that DAB+ sound is not as good as it could because the data rates used by most stations are 64kb/s or less, with only a couple of stations using 80kb/s. Well, the problem is that the Bush only has one loudspeaker which is about 95mm in diameter. Yes, it is only mono so that as far as listening to it as a normal radio, you can have all stations in one-dimen- sional monophonic sound and while it is reasonably pleasant it is no rival to a Bose radio. As you might expect, there is minimal bass and not a great deal of treble; it is pleasant but not hifi. I should state, though, that it still sounds better than most other DAB+ radios which typically have smaller speakers again and they are also usually mono to boot. Fortunately, the TR82DAB does have two 3.5mm stereo jack sockets at the right-hand side of the cabinet and these enable you to listen to earphones or headphones or you can feed its stereo line-level signals to an external stereo amplifier and loudspeakers. In this mode, first impressions are that the sound quality is quite good. DAB+ reception is generally cleaner and more noise-free than any equivalent stations on the FM or AM bands. However, on closer listening, switching between FM and DAB+, I have to say that DAB+ sounds more “restricted” and somehow lacking the finer detail of FM, especially when comparing the fine music stations. That is after allowing for the fact that the background hiss on FM can add to the impression of more treble. Apparent bass output is better than the internal speaker but there doesn’t appear to be much output below 100Hz or so. Finally, I should state that the DAB+ siliconchip.com.au is consistently much cleaner and better overall than AM reception, provided you have reasonable signal strength; if not, it will periodically drop out or just mute itself. Performance measurements We do not have facilities for measurement of DAB+ performance so we were restricted to limited measurements on the AM and FM bands. Nor does the radio have any external antenna connections so any measurements we we did were those with signals fed into the extendable whip antenna. Going to AM mode first, it was difficult to get any sort of signal into the radio but we did manage to measure the overall audio bandwidth. No surprises there; it is actually a bit worse than the normal mediocre bog-standard AM response: ie, 100Hz to 2.5kHz at the -6dB points. There was little point in trying to measure harmonic distortion, signal-to-noise ratio or anything else since the degree of coupling into the ferrite rod antenna from our signal generator was obviously very poor. On FM, we were able to do better. While we were not able to do sensitivity measurements, we were able to measure mono signal to noise ratio at 63dB while stereo signal-to-noise ratio was just a few decibels worse which is quite commendable really. Total harmonic distortion (mono) was typically around 0.5%, though rising markedly in the bass region below 100Hz. Frequency response is certainly much better than AM, as you would hope, but still well short of a good FM stereo tuner in the days of yore. With respect to 1kHz, the response is about +3dB at 5kHz, 0dB at 8kHz and -3dB at 10kHz. Below 1kHz, the response tapers to -6dB at 100Hz and then rolls off at 12dB octave below that. Considering that the Bush radio is using up-to-the-minute circuitry for its DAB+ reception, it is a little disappointing that the rest of its performance is fairly mediocre by comparison; it could so easily have been much better for possibly only a dollar or two in manufacturing cost. Still, so much consumer equipment these days is even more mediocre. The digital readout & all the controls except for the AM/LW/FM tuning wheel are in a recessed panel at the top of the cabinet. This is the view inside the unit with the front cover removed. Most of the parts are mounted on a single large PCB. Conclusion Overall, I have to say that the Bush TRD82DAB radio is an attractive unit and its performance is perfectly suited siliconchip.com.au to the vast majority of consumers. They will “love it”. Further information can be obtained from the local distributor, Bush Australia at www.bushaustralia. com.au It is well worth shopping SC around for the best price. September 2013  31