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Panasonic / National Panasonic,
Matsushita Electric Industrial Co. Ltd., Osaka
DR - 31 / RF - 3100 L

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überarbeitet am 21.10.2010

After their first receivers with digital frequency readout based on a conventional designed double conversion set equipped with a frequency counter, Panasonic presented the DR-31 / RF-3100 in 1982: a PLL synthesized receiver. The operation scheme of the DR-31 / RF-3100 is absolutely straightforward, the good performance on shortwave and ease of operation make this set a good catch when found on the used market for a reasonable price.

Double conversion, ZF 2 MHz, 455 kHz

Digital frequency display, 1 kHz, coverage 30 kHz - 30 MHz

AM, CW, USB/ LSB, FM (UKW)

Sensitivity SSB < 0.5 uV

Selectivity -6 dB
3,8 / 8 kHz

S Meter, RF Gain

The RF-3100 follows a travel receiver design, with all controls located on it's front panel, it looks like a small desktop receiver and can also be used for this purpose. With it's dimensions of 37,1 x 12,2 x 24,1 cm and it's weight of 3,2 kg it s too bulky to be used as a travel portable nowadays.
The RF-3100 can be powered from 110-125 / 220-240 V mains or 8 UM-1 / mono cells, the mains cable can be stored in a small compartment at the bottom face of the radio. The set is equipped with a carrying strap, as many travel radios from the eighties did.

The left part of the front panel space is taken by the 9 cm diameter speaker.
At the corresponding front panel space on the right, You find the huge tuning knob on the on/off pushbutton.
All other controls are located in the middle segment of the front panel: the display section with the analog signal strength meter, a red LED indicating sufficient battery (or mains) power and the blue fluorescent frequency display - the frequency is displayed wit ha resolution of 1 kHz. At the right, You find the band switch, on the European model with the setting VHF / FM band, LW (longwaves), MW (mediumwaves) and 29 shortwave bands, 1 MHz wide each. Three pushbuttons just below the frequency display switch off the meter illumination and the frequency counter for power saving reasons, switch the wide and narrow I.F. filter and activate the BFO.
In the bottom row of controls, You find from the left the headphones jack, the volume control, a double control for separate bass and treble, an R.F. gain control which will act rather as an attenuator, as the automated gain control cannot be switched of for manual gain control, and the PFO pitch control.

On the back of the receiver, You find the connectors for a long wire and a symmetric dipole antenna, a switch to activate the internal telescopic antenna and an DIN audio input / output jack.

With it's ten controls, the mains switch included, the operation of the RF-3100 is very simple and easy to learn: connect to mains, pull out the telescopic antenna (the switch at the rear should be set to telescopic antenna), press the power button and the red power LED will light and You hear a noise from the speaker. Use the shortwave band segment switch for the first (MHZ) digit of the desired shortwave frequency, use the main tuning control to tune in to the kHz digits, when You arrive at 1 5 5, You should hear Vienna's shortwave signal.
The sensitivity is very good with the internal telescopic antenna. The receiver does not tolerate lond wire antennas to well: in crowded bands (like the 49, 31 or 25 m shortwave band) during the night hours, the receiver front end tends to overload, so You must use the R.F. gain control to prevent Your signal beeing covered up from adjacent strong stations.
The two I.F. filters have not really steep skirts, but the are well suited for shortwave broadcast stations reception, the narrow filter will separate two 5 kHz channels nicely.
SSB reception using the BFO reception is possible, but it cannot really be enjoyed as the radio showas a significant drift: according to the manual, it should be 500 Hz after warm up, I found my set drifting 2 - 4 kHz during an hour.

According to the age and the design of the receiver, a clock/timer and digital frequency memories are lacking; as a simple shortwave and VHF receiver, the RF-3100 does it's job really well and can be recommended when found for a reasonable price on the used market as an entry or secondary receiver.

further literature:
e: WRTH tests popularly priced receivers, Panasonic RF - 3100, Larry Magne, WRTH 1983
d/e: Panasonic DR-31 at www.radiomuseum.org

© Martin Bösch 13.7.2010