überarbeitet am 21.10.2010
National Panasonic had a similar success with it's world band radios with it's production
in Japan as Grundig and Nordmende had in Germany. The sets from Panasonic and the ones
from it's competitor in Japan, Sony, usually had a good price - performance relation
and did win a reasonable part of the market after a few years. Most of the Panasonic
sets came in an acceptable price range, they offered no unnecessary features but
a good conventional receiver concept and a useful frequency counter.
After theDR-22 with a crystal calibrator and a mechanical
frequency display, Panasonic brought out it's DR-28 / RF-2800 in 1978 - a portable set with
an electronic frequency counter. This set was quite popular in Switzerland, You find more
of them on the used market then of DR-29 / RF-2900
a nearly identical receiver with a preselector to improve performance in the presence
of high sortwave signal levels (as found in Central Europe).
Double conversion superhet
, I.F. 2 MHz, 455 kHz
Digital frequency display, 1 kHz
AM, CW/SSB (BFO), FM
MW 32 uV,
5-30 MHz AM 1,8 - 2,4 uV, SSB 1,1 - 1,4 uV
Selectivity (-6/-60 dB)
3,8/13,1 kHz, 8,1/27,3 kHz
S Meter, RF Gain
The National Panasonic DR-28/ RF-2800 is a portable shortwave receiver, it's
dimensions of 38 x 25 x 12 cm and it's weight of 3,6 kg make it "portable" in the strict
sense of the word. The DR-28 has been constructed in a time, when a traveler's
radio needed two big handles to protect front panel controls when the set is
stored under an airplane seat...
The receiver can be powered from 110 / 220 V mains or 6 UM-1 / mono cells.
At the left part of the front panel, the space is taken by the speaker grille,
audio quality is good thanks to an output power of 2.3 Watts.
At the top of the right half of the front panel, You find the rotating analog frequency
dial with coarse markings that give You an impression, to which part of the shortwave
spectrum You are tuned to. Next to it, You find the green - blue fluorescent
frequency display with a resolution of 1 kHz.
In a row of controls just below, You find from the left the mains switch, the
dial illumination and tha wide and narrow I.F. filter switch. The signal strength
meter tends a bit to overestimate signal strength, next to it, You find the bandswitch
and the switch to turn of the energy consuming frequency display, this might also
be helpful in case of "birdies" caused by oscillations from the frequency
In the middle, You find the huge main tuning knob, it can be pulled out to activate
a geared fine tuning mechanism. It it's left, You find the big volume control and
slighly smaller separate bass and treble controls and the connectors for an
external speaker and a cassette recorder.
The control at the right SW CAL ist used to calibrate the frequency display,
in fact it corrects the frequency display's reading to the frequency that is
actually received. As the control range is quite big, it can happen, that the frequency
displayed is up to 5 kHz off the reading of the frequency counter. So make sure,
You first tune in to a stations with a known frequency in a shortwave band,
carefully tune for maximum reading on the signal strength meter and then
adjust the reading of the frequency display to the known station's frequency.
The R.F. control is used to vary the high frequency amplification, in fact
a kind of automatic gain control is always active, so the RF gain control
is merely used like a step - less attenuator in the case of the presence of strong
signals. As the DR-28 tends to overload with high signal strength, this might be
the case from time to time in central European winter nights on 49 meters. The
BFO has a separate switch and beat note control.
The R.F. signal coming from the antenna has to pass a first amplifier stage
and the RF gain control to be fed to the first mixer. After I.F. amplification
the signal is mixed to the widely used 455 kHz as second intermediate frequency.
In AM mode, a diode demodulation is used, for CW and SSB reception, the BFO's
signal is added before demodulation. The oscillator frequency from the first
mixer is used to drive the frequency counter.
The DR-28 does a good job as a simple world band receiver that can meet
some DXer's expectations. The capabilities to handle high signal level situations
are limited, although. The DR-28 tends to spurs and "ghost signals"
appearing on strange positions on the dial. Especially with a long wire antenna
connected, the receiver tends to overload: You have to reduce the R.F. gain
to end with a S meter reading between 8 and 10.
The switchable preselector of the DR-29 / RF-2900 does improve the behaviour
in high signal strength conditions, but even with the preselector activated,
the DR-29 cannot cope with long wire antennas longer then 5 - 7 meters.
The sensitivity is quite good, selectivity is fair with the narrow filter,
the WIDE filter can only be used on channels without interference from
The DR-28 shows a slight drift, it may be detuned up to 4 or 5 kHz after
one hour of use, automated recordings of single sideband transmissions or even
decrypting radioteletype signals with a converter might be found difficult
or even impossible.
The fact, that the real and the frequency displayed from the counter might
have a difference of up to 4 or 5 kHz reduces the benefit from the frequency counter.
The performance on the VHF / FM broadcast band ist good, especially in comparicon
with other sets doming from Japan.
In conclusion: the DR-28 / RF-2800 and even more the DR-29, a similar set
equipped with a switchable preselector, is a really useful shortwave radio for
listeners interested in getting some informations directly from abroad from
the External services of the major international shortwave broadcasters and
even for DXers for their first steps in the Hobby. For everyday and travel use,
a PLL synthesized receiver with some memories and without the drawbacks of the
frequency counter shift and poor performance under high signal level conditions,
might be the better option.
On the used market, the DR-28 can be found quite frequently in Switzerland,
the DR-29 with the preselector would be even a better discovery, if the price
|Variants sold in different regions of the world:|| |
||DR-28 / RF-2800 LBS||blue fluorescent display,|
longwave band, FM 87,5 -108 MHz
||RF-2800||rote LED display active only in shortwave bands,|
no longwave coverage, FM 88 - 108 MHz
||RF-2900||blaue fluorescent display active in all bands,|
no longwave coverage, FM 88 - 108 MHz
||Proceed 2800||rote LED display, active only on the shortwave bands,|
no longwave coverage
© Martin Bösch 13.7.2010