National Panasonic DR-48 / RF-4800

Manufactured by National Panasonic, Osaka.

The Panasonic DR-48 / DR-49 receivers were the last in the series of Panasonic station receivers still using conventional technology and without PLL frequency synthesis. In the shortwave ranges, the operation frequency is decoupled and fed to a frequency counter.
The sets DR-48 and DR-49 differ in the design of the frequency display; the red LED display of the DR-48 is only active in the shortwave ranges SW 2 - 7.

Variants

DR-48 / RF-4800 LBS, European version: red LED display, active only in the SW ranges; long wave (two ferrite antennas), FM 87.5 -108 MHz
RF-4800, USA version: red LED display, active in SW ranges only; no long wave (one ferrite antenna only), FM 87.5 -108 MHz
Proceed 4800, Japan version: red LED display, active in SW ranges only; no long wave, FM 76 - 90 MHz

Technical data

Principle: Single conversion up to 3 MHz; Double conversion above 3 MHz, IF 2 MHz, 455 kHz / FM 10.7 MHz
Operation modes: A1, SSB, AM (A3), FM (F3)
Frequency range: VHF, LW, MW, SW1 (1.6 - 3 MHz), SW2-8 (3 - 28 MHz)
Frequency display: digital display, 1 kHz
Frequency memory: none
Signal strength indicator: S-meter
signal processing: RF gain
Features
Sensitivity: AM (A3) MW 60 μV; 5-30 MHz 1.1 - 1.4 μV, SSB 0.6 - 1.0 μV / Selectivity: 1.7/6.0 resp. 2.5/15 kHz (-6/-60 dB)

Power supply

Mains operation: 110, 220 V; 12 V =.
Batteries: 8 x 1.5 V (UM-1)

Dimensions

480 x 200 x 355 mm, weight 8 kg

Accessories

Operation

The Panasonic RF-4800 was marketed in Europe as the DR-48, which also covers the longwave range.

At 48 x 20 x 35.5 cm (wxhxt) and 8 kg, the landscape-format station receiver is one of the large and only theoretically portable sets. Two handles at the front of the black lacquered sheet-steel cabinet provide a certain mechanical protection for the operating elements. In addition to a mains input that can be switched from 110 to 220 V, the RF-4800 also has a 12V car battery connector and its two battery compartments hold 8 UM-1 batteries.

On the left of the front panel is the large loudspeaker, below it the mains switch and the 3.5 mm jack sockets for an external speaker and the tape line out. To the right are the rotary controls for volume, bass and treble and the BFO control.

In the centre of the large dial, there is a window for the red LED frequency display, to the left of which are the coarse dials for longwaves (only on the European model DR-48), mediumwaves, SW1 (1.6 - 3 MHz) and the FM broadcast band, to the right the coarse dials for the seven shortwave ranges, in each range 4 MHz are covered.

Directly in the centre of the front panel is the huge main tuning knob, equipped with a crank, when the centre is pressed in, the tuning speed is set from slow to fast. To the left of it, you find the tuning knob for the ranges on the left coarse dial, the LW, MW, SW1 and VHF ranges, in all these ranges the DR-48 works as a single conversion superheterodyne. Belows the small field strength meter, which is calibrated in S-steps and - typical for Panasonic sets - tends to read generously high, there are three toggle switches. The left one actiavtes the AFC on VHF, in AM mode it selects the wide or the narrow IF filter, the middle one activates the noise limiter, the right one the BFO used for SSB and CW reception, the pitch of the CW tone or the subcarrier is set with the BFO pitch control below. To the left of the BFO control is the row of volume / tone controls.

Below the right coarse dial, the band switch LW - MW - SW1 - FM is located at the right and the band segment switch at the left, with its positions SW 2-8, seven 4 kHz ranges are selected. In these ranges, the DR-48 works as a double conversion receiver. In case of a station with a known frequency or with the signal of the time signal transmitters WWV/WWVH on 5 or 10 kHz, the frequency display can be calibrated to maximum S-meter deflection with the SW2-8-CAL control, in case of a detuned control, the frequency display can be 2 - 3 kHz off the actual frequency.

At the bottom right, below the band range switch, are the knobs for antenna tuning and the RF gain control, which must be set to DX at the right stop to receive weak signals. Three toggle switches under the type designation activate the dial illumination, the frequency display and set the meter to display battery voltage.

On the rear of the DR-48, the two separate fold-out ferrite antennas for medium and long waves and the terminals for VHF, LW/MW and SW2-8 antennas are located. For the latter shortwave ranges, the receiver also has a PL/SO 239 socket. An audio signal can also be fed to the DR-48 for playback via a DIN tape jack; the PHONO / RADIO switch sets the radio to playback of the external source. Finally, there is a 12V DC input and the mains connector which in the European version is switchable.

The operation of the DR-48 is simple: the RF gain must be set to DX at the right stop, the volume control is set to a medium-loud noise, the bandwidth switch above it to WIDE, the mode switch to AM. Use the bandwidth switch to select the shortwave ranges SW2-8, for reception of Austrian Radio on 6155 kHz select range SW2, use the tuning knob to bring the display to 6.155 and off you go. If the signal strength maximum is on a frequency 1 or 2 kHz higher or lower, the set is tuned exactly to 6.155 and the counter is calibrated to signal maximum by ear while observing the S-meter deflection with the SW2-8 CAL control.

During warm-up, the receiver shows a certain drift, which is especially noticeable in SSB reception. The receiver slowly moves from a tuned frequency, a phenomenon which no longer occurs with the more modern receiver concepts with PLL circuitry.

The filter skirts of the IF filters used cannot keep up with the filters of modern sets; accordingly, interference whistling often occurs.

Due to the single conversion principle, mirror signals can occur at frequencies below 3 MHz. Since the internal ferrite antennas cannot be switched off on LW and MW, the DR-48 is not a great medium-wave DX receiver.

In summary, the DR-48 / RF-4800 as a tabletop receiver was a state of the art set in the early 1980s, the receiver has no special highlights such as outstanding stability, steep-edged filters, suitability for portable use. For the reliable performer, the original catalogue price was too high. At a reasonable price, the Panasonic can still serve the newcomer to shortwave reception well and is still an impressive receiver forty years after its market launch.