RADIO SHACK REALISTIC 12-1909
by Julian Hirsch and Christopher Greenleaf
FADING the current Radio Shack line of car stereo components is the new Realistic Model 12-1909 cassette player/receiver. The tape section features solenoid-activated autoreverse, Dolby B, switchable equalization (normal or chrome/ metal), and automatic disengagement of the pinch-roller when the car's ignition is switched off. The fast-wind controls and eject button are mechanically activated.
The quartz-locked frequency-synthesis AM/FM tuner features phase-locked-loop FM stereo reception, six preset buttons each usable for one AM and one FM station, and a yellow LED frequency display that doubles as a twelve-hour digital clock (the time is normally displayed except while tuning or for a few seconds after pressing the frequency-display button). Rocking the tuning knob to either side advances the tuner up or down the spectrum in the usual increments (0.2 MHz for FM, 10 kHz for AM).
When the knob is pushed, the tuner seeks the next receivable station up ward; if the knob is held in, the tuner continues scanning upward until the knob is released.
The receiver has center-detented treble, bass, and balance knobs. The loudness button boosts the response 9 dB at 125 Hz and 5 dB at 6,300 Hz. There is a mono button for FM, and indicator lights show tape direction, radio band, stereo reception, noise reduction on, and memory on (for programming the presets).
There are connections for ignition-switched power, grounding, clock and memory maintenance power, a trigger lead for an external power amplifier or an automatic antenna, and the antenna lead itself.
The built-in amplifier is rated to deliver 15 watts per channel into 4-ohm loads. The four speaker wires, which must be carefully isolated from the car's ground and from each other, can lead either to a pair of 4-ohm speakers or (with Radio Shack's optional balance/fader attachment) two pairs of 8-ohm speakers.
The Realistic 12-1909 measures 1 3/4 inches high, 7 3/32 inches wide, and 6 inches deep. Like all Radio Shack products, it is available only in Radio Shack stores.
Price: $249.95.
Radio Shack, Dept. SR, 1700
One Tandy Center, Fort Worth, TX 76102.
Lab Tests Like a number of other car stereo manufacturers, Radio Shack rates its products' FM performance using various unofficial (and undefined) test procedures that sometimes pre vented us from comparing our test results with the published ratings.
Nevertheless, we found that the Model 12-1909's FM section performed in a very satisfactory manner. Although its distortion was not as low as that of most home receivers, it was fairly typical of car radios, and the usable sensitivity and 50-dB quieting sensitivity were quite good. Image rejection was far better than rated (84 dB versus 43 dB!), but the very good AM rejection was somewhat offset by a merely fair capture ratio.
The alternate-channel selectivity was highly asymmetrical, measuring 100 dB on one side of the signal and only 51 dB on the other.
Although we do not ordinarily ad just the generator frequency when measuring the selectivity of a digital-synthesis receiver (since in actual use neither the tuner nor the station frequency can be adjusted to optimize performance), we did con firm that the lopsided selectivity was the result of tuner (mis)alignment in our test sample rather than tuning error.
The FM tuner has an automatic channel-blend circuit that resulted in effectively mono reception at moderately low signal levels, al though the stereo light remained on until we dropped the signal to 16 dBf (1.75 microvolts). This effect also is typical of car radios, whose stereo indicators show only that the station is transmitting a stereo pilot carrier (not necessarily a stereo pro gram) and say nothing about whether the output to the speakers is stereo or mono. We did find that the FM channel separation of the Mod el 12-1909, more than 45 dB in the midrange, far surpassed its 30-dB rating. The AM tuner section's frequency response was somewhat un usual-a prominent peak at 80 Hz along with the typical early rolloff of high frequencies.
The audio amplifier, measured through the FM tuner (we used 30-percent modulation in an unsuccessful effort to reduce the tuner distortion sufficiently to reveal amplifier distortions), had good tone-control and loudness-control characteristics. At 1,000 Hz the output clipped at 12.25 watts into 4 ohms and 8.8 watts into 8 ohms. Although this did not quite match the manufacturer's 15-watt rating, the discrepancy was negligible by the usual standards applied to car radios.
The tape deck had an excellent frequency response with both nor mal (120-us) and chrome/metal (70–us) equalization. There was a small difference between the response measured in the forward and re verse directions (it was flatter in reverse) but not enough to affect the listening quality significantly. Judging by the relatively steady output level at high frequencies, the tape-
to-head contact was good. The flutter was somewhat lower in reverse but was satisfactory in either direction. Tape speed was 0.6 percent slow in either direction and at any part of the tape.
With the noise reduction off, the tape signal-to-noise ratio (S/N) was 55 dB A-weighted and 46.5 dB CCIR weighted. The Dolby system improved these measurements by 9 to 10 dB. Using the chrome/metal equalization added another 1-2 dB to the S/N figures. The fast-forward and rewind speeds were slightly faster than rated, 127 instead of 140 seconds for a C-60 cassette. J.H.
Road Tests On the road, the Realistic 12 1909's digital tuner provided quick, firm, and accurate station selection using any of its three tuning modes:
manual, seek, and scan. Its FM stereo performance was fairly immune to the worst interference effects of city driving, and outside the city I was able to get listenable stereo out to average limits (20 to 30 miles) under normal reception conditions.
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HIRSCH-HOUCK LAB MEASUREMENTS
FM mono usable sensitivity (75-ohm input):
18 dBf (2.18 µV)
Mono 50-dB quieting sensitivity (75-ohm input): 18.3 dBf (2.26 µV)
Stereo 50-dB quieting sensitivity (75-ohm input): 26 dBf (5.5 µV)
Tuner signal-to-noise ratio at 65 dBf: 72 dB
Tuner distortion at 65 dBf: 0.84%
FM frequency response (-3-dB limits): 20 to 16,000 Hz
Stereo separation at 100, 1,000, and 10,000 Hz (at 65 dBf): 38, 45, and 30 dB
Capture ratio of 65 dBf: 3.9 dB
AM rejection of 65 dBf: 72 dB
Alternate-channel selectivity: 51 dB
Adjacent-channel selectivity: 2 dB
Image rejection: 84 dB
AM frequency response: 37 to 2,300 Hz 6 dB
Tape-playback frequency response (standard BASF rest tapes, -3-dB limits): 120-us EQ, 32 to 15,000 Hz forward or reverse; 70-µs Eq, 32 to 17,000 Hz forward, 32 to 18,000 Hz reverse
Tape signal-to-noise ratio (referred to 250 nWb./m at 315 Hz, 120-µs EQ): unweighted, 50 dB; Dolby B and CCIR/ARM weighting, 56 dB; Dolby B and A-weighting, 64 dB
Flutter. forward, ± 0.22% CCIR-weighted peak, 0.13% uS-weighted rms; reverse, 0.18% CCIR-weighted peak, 0.1% RS-weighted rms
Tape speed accuracy: -0.6%
Fast rewind time for C-60: 127 seconds
Tone-control range: + 10,-11 dB at 100 Hz; +9.6,-13 dB at 10.000 Hz
1,000-Hz clipping-power output into 4 ohm: 12.25 watts
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Using the FM mono button (a most welcome option) extended the range a bit, to around 40 or 45 miles, but not to the 50-mile limit I have sometimes achieved with other, more costly tuners.
Whatever high-blend circuitry is included to quiet FM stereo appeared to work in an on/off fashion rather than continuously. It was, therefore, fairly obvious when it cut in, but the effect was not bother some. Overall, the FM sound was typically clear, with well-reproduced natural timbres. Shielding against impulse noise on the FM band was less than optimal, as passing motorcycles and traffic-signal switching demonstrated throughout our test drives. AM reception was also noise prone as well as slightly muffled except near a strong transmitter. The preset buttons are quite close together, leading to a mis selection now and then, but other wise the radio was simple and comfortable to use.
Tape play in both directions was smooth and for all practical purposes indistinguishable. The pitch steadiness was fairly good, with only a slight lack of firmness in certain piano or organ tapes: the sound was stable with all other kinds of music. The Dolby system worked well with all three tape types (nor mal, chrome, and metal) that the deck handles.
The tape transport was reason ably insensitive to vibration from stone-block streets and old tram rails. There was just one surface it did not handle with aplomb-a washboard country road in Connecticut disrupted a Joni Mitchell tape badly enough to make me shut it off. Of course, my Volvo creaked and protested the road surface too, as did my passenger, so we returned to more gentle roads.
To test the player's handling of flimsy tape, I slipped an old C-120 into it one frosty morning and successfully played through both sides using autoreverse. (Of course, we don't advise readers either to play tapes longer than a C-90 or to pop their favorite cassettes into a cold transport, but we regularly try this "torture test" just to see if the player and tape emerge unscathed.) Like most car tape players with auto-reverse, the 12-1909 keeps playing a cassette until you tell it to stop.
Although shutting off the ignition disengages the pinch-roller and backs the head out a bit, the tape remains in the bay until you eject it manually. When there is power and a tape is in, the player is on. The radio, on the other hand, comes on only when you push the volume knob--a welcome feature if, like me, you don't want an onslaught of radio noise whenever you change cassettes! The integral amplifier appears to be a good one. Crisp transients from harpsichord and Fender bass alike failed to strain the 4-inch Philips speakers in my car. At home, connecting the Realistic 12-1909 to a pair of B&W bookshelf speakers confirmed my impressions on the road. There was a fine, open quality to the sound that I don't normally expect to encounter from receiver/ tape players in this price class.
Reaching very good listening levels was not a problem, and the amplification did not fall to pieces when pushed near its limits. The receiver let me know it was sweating at high volumes, but its sound remained musical.
For its price, and considering the ease of installation (helped by a good manual), the Realistic 12-1909 is a bargain. It lacks only the kind of refinement that many more hundreds of dollars will sometimes buy. Aside from a brief squeal as the autoreverse engages, the mechanism works simply and silently. In fact, my only substantial criticism is that the loudness control and the bass and treble tone controls coincide in their effects, making subtle adjustments hard to achieve. But if your budget is modest, the 12-1909 has a lot to offer.
-C.G.
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