Manufactured by National Panasonic, Osaka.
What Grundig did in the European market with its portable world band receivers, the Japanese company Matsushita did with its world band radios sold under the brand name National Panasonic. These and also the world band receivers of the main competitor Sony contributed to spread interest in short-wave reception with their good price-performance ratio. Thanks to the use of a frequency counter, which was for the first time affordable, precise frequency reading and tuning now was possible.
The DR-22 with its crystal calibrator and calibrated fine tuning dial was followed by the DR-28 in the year 1978, a portable receiver with digital frequency display. The DR-29 had an additional switchable preselector integrated in the upper area of the speaker grill to improve the large signal behaviour.
The DR-28 / RF-2800 measures 38 x 25 x 12 cm and has a weight of 3.6 kg. Two handles or protective bars on the sides protect the front of the unit if the receiver has to be pushed under the seat of an aeroplane on the way to the holidays… The DR-28 can alternatively be operated from 110/220 V mains power or with 6 UM-1 batteries.
The left part of the front panel is dominated by the large loudspeaker grill, the sound is above average with 2.3 W sine power. At the top, side by side, are the two windows for the analogue coarse dial with markings for the most important broadcast bands and next to it for the five-digit blue-green fluorescent display, which indicates the reception frequency with an accuracy of 1 kHz.
In the next row, the mains switch, the switch for the dial illumination (can be turned off to save battery power) and the bandwidth switch for the narrow and wide IF filter are located next to each other. The analogue S-meter tends to read high. At the right, the operation mode switch and the switch to turn off the frequency display (also to save power and to avoid interference caused by the meter's electronics).
In the middle is the large and easy-to-grip main tuning knob, for fine tuning the whole knob can be pulled out, activating a backlash-free 1:20 reduction. To the left of this, the large volume control and separate controls for bass and treble are located. To the right of the tuning knob, three controls are arranged one above another. With SW-CAL, the calibration of the frequency counter can be shifted up to 5 kHz and can be calibrated by means of a signal generator or a transmitter on a known frequency. With the RF gain, the RF amplification can be reduced if strong transmitters lead to overload; the BFO control is used for CW and SSB reception.
The signal coming from the antenna is amplified in an RF amplifier stage and is fed to the first mixer. After being converted to the second IF and having passed the IF filters, the signal reaches the AM detector stage, here the subcarrier generated in the BFO is mixed for SSB/CW reception. After the tone control, the audio signal from the final amplifier is fed to the loudspeaker. The oscillator frequency is decoupled in the first mixing stage and fed to the frequency counter module.
In practical use, the DR-28 is a convincing simple but DX-capable world band receiver with good audio. In the DR-28, with its wideband front end, the large signal behaviour is poor, so that overloading and „mirror stations“ can occur. Especially when an external long-wire antenna is connected, the signal must be attenuated vigorously with the RF gain until the S-meter, which tends to exaggerate anyway, indicates between 8 and a maximum of 10.
Thanks to the switchable preselector in the RF-2900 model, the danger of overload is somewhat reduced with this receiver, but even the DR-29 with its preselector cannot cope with really long long-wire antennas; it should not be expected to handle more than 5 - 7 metres of wire.
The sensitivity is quite good, the selectivity in crowded bands is only acceptable when the narrow IF filter is in use. The wide IF filter with its very wide skirts should only be used on frequencies with free 5 kHz adjacent channels. The receiver has a tendency to drift slowly after switching on as well as during operation. As the frequency can shift by up to 4 kHz in one hour and even when touching the rod antenna, single sideband reception is difficult. ECSS reception, where AM signals are mixed with the BFO carrier and the SSB demodulator is used, is not possible with the DR-28. The frequency on the display may differ slightly from the actual operation frequency, so after a frequency announcement, the signal must be adjusted to maximum with the SW-CAL control. Performance in the FM broadcast band with the high resolution of the frequency display is quite good im comparison to other Japanese sets.
In summary, the DR-28 and especially the DR-29 equipped with the additional preselector is a good world band receiver for the beginner who wants to do simple DX and also listen to SSB signals in amateur bands and who can do without all the achievements of digital technology such as memory and clock functions. Compared to small travel radios, the selectivity and sensitivity as well as the audio from the large loudspeaker are considerably better, so that a DR-28 purchased at a bargain price gives an exciting introduction to worldwide short-wave reception.
Double conversion superhet, digital frequency counter.
The set is equipped with semiconductors.