Following in the steps of the mythical GE "Super Radio" receivers, Radio Shack is now selling its contender for the BCB listener; the OPTIMUS 12-603A "Tuned RF AM-FM Extended Range Receiver".  It is a mid-size portable AC/DC radio intended for those who want a little more performance than most portables tend to deliver.  While falling somewhat short of the reception requirements of some serious BCB DX-ers, this fairly simple radio does offer relatively good reception similar to that of the GE Superradio III and excellent audio quality in a mono receiver.

FEATURES: This big black radio is about 13" long, 9" high, and 3.5" deep,  weighing in at about 4.5 pounds without batteries.  It covers 530 to 1700 khz on the AM band, and 88 to 108 Mhz on the FM broadcast band.  The upper part of the front panel has a standard non-illuminated slide-rule analog dial with underlying log scale for frequency determination, and tuning is done via a large knob on the right side of the radio.  I had little difficulty in adjusting the tuning for stations only 10 khz apart on the AM band, so the tuning action is fairly easy, but slightly stiff in feel.  The left side of the radio's front panel has the switches for AFC (FM), AM/FM band select, and AM bandwidth (Wide/Narrow), along with knobs for Treble, Bass, and Volume.  Surprisingly, the main power switch is a silver button on the top of the radio, rather than being part of the usual off/on/volume control.  This layout of the controls and front panel looks a bit like an attempt by Tandy to imitate the look of the GE SuperRadio III.  Indeed, side-by-side, they do look a lot alike.  However, the big white frequency markings and correct dial alignment made the slide-rule display of the Optimus easier to read in dim light than the one on the Superradio III.  The rest of the front panel is occupied by a large speaker grille containing a nice 4.5 inch speaker and a tiny 1.5 inch wide "tweeter" to its upper left.  These speakers are slightly smaller than those on the Superradio III, but still deliver good performance. The top of the radio has a plastic carrying handle, the power switch, and a 33 inch long telescoping whip for FM broadcast reception which can be tilted or swiveled in almost any direction.

   The back of the receiver has screw terminals for both AM and FM external antennas (high impedance twin lead or long wire and a shorting bar for the telescoping whip).  The battery compartment sits in the lower half of the back of the radio, and has a removable hatch which also allows for storage of  the AC power cord.  The radio runs on AC with its own internal AC power cord, nd can be quickly switched to DC battery operation via a small recessed switch on the left side of the back of the radio.  The radio requires 6 "D" cells, but has no external 9V DC jack, so you are limited to either AC or internal battery DC power.  There is also a 1/8th inch earphone jack located on the right side of the radio which is monaural, even on FM broadcast.

PERFORMANCE: On a whole, the radio does work fairly well, and seems to be designed more for the long-range BCB listener rather than the true DXer.  One of the first things you notice when you first turn it on is that the audio quality on AM is extremely good, rivaling units quite a bit larger in size.  This fine audio quality is what makes the radio worth owning if you like BCB listening.  With the Bass turned up, the radio really booms out its sound, and has plenty of audio power to fill a room.  However, near full volume, the audio amplifier does top out, causing notable distortion when you are pushing it past its limits.  The Treble and bandwidth controls are also useful in reducing the effects of mild thunderstorm static by turning the treble down or reducing the bandwidth.  The bandwidth control appears to be a true one, and not just audio tone limiting, as adjacent strong station interference was reduced in the narrow setting.  Many distant stations came in as clearly as locals, with really fine audio.  I really enjoyed listening to the clear crisp audio from an episode of "WHEN RADIO WAS" on KSL in Salt Lake City (750 miles west of my home in Nebraska), so the radio does very well for long- range listening on the more powerful stations.  Music sounded good, and I also enjoyed listening to several major league baseball play-by-play broadcasts with their improved sound.  The audio was better than both my Yaesu FRG-7 and my Sony ICF-SW7600G, so if you enjoy hearing quality sound from both local and more distant stations, this radio might be a good one to get.  FM broadcast audio was also good, but was only monaural, and these days, stereo FM is almost manditory for quality listening.  Using the "wide" bandwidth mode, the audio quality improved a bit more, but the selectivity really suffered, so for listening to stations other than the local ones, the "narrow" bandwidth selection is best.

   However, those of you who like to do more serious DX-ing might be a bit disappointed in the Optimus 12-603A's technical performance.  The receiver is indeed MUCH more sensitive than many other commonly available portables in its size class, but the receiver may not be quite sensitive enough for digging out some of the really weak stations.  In comparison to my Sony ICF-SW7600G (on its internal loopstick), the Optimus was simply not quite in its league.  While listening to KSL as it took a deep fade, the SW7600G began to pick up KENS, a weak sports/talk station in San Antonio, Texas, in the background of KSL's audio along with the usual garbled noise from the numerous other stations on 1160.  However, with the Optimus, KSL just faded away almost completely for nearly a minute, with only faint hints of other activity on the frequency.  I had to crank up the volume on the Optimus 12-603A just to hear KSL at all during the deeper parts of the fade, and for short periods, the station was inaudible.  This deep-fade problem was also noted on several other broadcast stations.  I never completely lost KSL with my Sony (although it was occasionally hard to hear clearly due to the other stations' audio), so the 7600G was definitely outperforming the Optimus.  When KSL was back out of the noise on both receivers, it seemed to have a steadier signal on the Optimus, so its AGC may have a longer time constant than the Sony's.  Some of the rapid but minor signal fluctuation in the Sony is probably due to it hearing the effects of the numerous other stations on 1160, where the Optimus was only hearing KSL.  I noted in the area between 800 khz and 600 khz, well away from the big-gun stations, there would be a few rather blank spots on the dial using the Optimus, while the 7600G easily picked up at least some activity on every single 10 khz channel throughout the entire AM broadcast band.  Doing a direct comparison between the Sony and  the Optimus using a signal generator for a weak signal source on 860 kHz revealed that the Sony was about 2.7 dB more sensitive than the Optimus.

  At night in the expanded portion of the band (1610 to 1700 khz), there isn't much in the way of activity in this part of Nebraska, so this area is a fairly harsh testing ground for BCB receivers.  In the expanded band, the Optimus clearly received only our local TIS from the Homestead National Monument and the much weaker KCJJ in Iowa City (at 275 miles out, it needed nearly full volume to be heard).  Other than that, only faint hints of signals from two other stations could be heard, even with the volume cranked all the way up and my ear against the main speaker.  In contrast, the Sony ICF-SW7600G picked up the local TIS and about 8 other stations fairly easily in the expanded band.  The Optimus also showed some "lateral" bleed, with the local TIS station fading away more slowly above its frequency than below it.  This interference may have helped to blot out the extended-band stations.  In direct comparison to the GE Superradio III, the Optimus was not as  sensitive in the extended portion of the AM band as the Superradio, although otherwise, the performance of the two radios was quite similar.

   Daytime use further showed the difference in sensitivity between the two radios, with the 7600G just catching some weak stations the Optimus couldn't.  Even when both radios could hear the same weak station, that station would seem to be louder and easier to hear with the 7600G.  Adding an external antenna helped the Optimus quite a bit, making it easier to do some DX-ing, but it still didn't quite match the Sony's ears.  Even my old Yaesu FRG-7 attached to my 40 meter dipole was performing a bit better than the Optimus in almost every respect except perhaps audio quality.  I feel the Optimus "seems" to perform better to some listeners because of its better audio response and wider bandwidth, coupled with its reduced ability to hear the weak level of thunderstorm static or other weak interference that other communications receivers pick up easily.  Indeed, the radio has a very low noise floor (much quieter than the GE Superradio III's raspy hissing background), making it very pleasing to listen to.  Its sensitivity is quite adequate for most long-range listening and for casual BCB DX-ing with an external antenna, but for serious DX-ing use, the Optimus may not be quite sensitive enough.

   The OPTIMUS 12-603A also lacks a bit of the fine selectivity needed for the serious DXer, sometimes being unable to cleanly split strongly unequal signals at 10 to 30 khz separation.  My Sony ICF-SW7600G was definitely more selective than the Optimus, easily doing 10 khz station splits (and some narrower).  The Optimus still showed a little weak side-channel interference from our local 1 kw KWBE (1450 khz at 4 miles) to a Lincoln 1 kw station KLMS (1480 khz at 38 miles) at some antenna orientations which weakened the KLMS signal and put the KWBE signal near its strongest broadside to the internal loopstick.  The radio had more trouble with the more distant 5 kW KRGI on 1430 kHz, only being able to pick it up cleanly when the end of the Optimus was pointed at KWBE's tower to put KWBE in the antenna null.  However, the image rejection of the Optimus on AM was better than the Sony, as the Sony showed a weak IF image of  KWBE at 540 khz, and the Optimus did not.  The loop-stick nulls of the Sony were a bit sharper than those of the Optimus, with the Optimus showing a slightly more gradual falloff in signal strength as you approached its end nulls.  One very nice null feature of the Optimus is that one of the nulls (the one off the main tuning knob) tends to be somewhat deeper than the other one, making it possible to null a particular station and still hear stations in the opposite direction from the primary null.  These nulls were deeper and better than those on the GE Superradio III, so the Optimus was not as bothered by multi-station interference as the Superradio was.

    Sadly, on FM broadcast, the Optimus 12-603A had only fair to mediocre performance when it comes to broadcast FM DX.  While the audio was good, the receiver had only moderate sensitivity when compared to the Sony ICF-SW7600G.  The Sony picked up stations on over 50 channels on its whip, with some over 100 miles away, while the Optimus only got about 35, with most of them under 90 miles distant.  When the Sony SW7600G was hearing weaker stations, some frequencies showed more than one station as you re-oriented the whip antenna.  The Optimus couldn't match that performance, and its AFC would frequently lock onto a stronger adjacent channel station, preventing the weak signal from coming through.  Weaker signals weren't just noisier; they also had somewhat diminished audio levels, making listening more difficult.  Again, a high external antenna helps the Optimus on FM, but the unit did not have quite the selectivity of the Sony, so the Optimus is definitely not an outstanding choice for someone who is serious about FM DXing.  The lack of FM stereo reception ability with headphones (often available in many small portables), and unremarkable sensitivity are a bit disappointing, but I suppose that comparing a $60 radio with a $190 high-performance model might be just a bit unfair.  The FM performance is adequate for the causal listener, but I like my Sony a lot more for pushing the limits of broadcast FM reception.

   In summary, the OPTIMUS 12-603A is a good portable radio with excellent audio quality for listening to distant AM BCB stations.  However, its lower selectivity, and weakness in digging out weak signals and keeping deeply-fading ones from vanishing make this a radio which will probably not satisfy the requirements for hard-core DX-ing use.  The GE Superradio III performed very much like the Optimus 12-603A, and in my opinion, as true "DX-machines", they are both a bit overrated.  At $59.99, the Optimus is best purchased on sale ($39.95), as it is a bit overpriced for what it gives you.

David Knisely, KA0CZC

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