National Panasonic DR-31 / RF-3100
Manufactured by National Panasonic, Osaka.
After their first world band receivers with digital frequency display, which were based on a conventional receiver design with a frequency counter, Panasonic introduced the RF-3100 in 1982. It was the first set of a new receiver generation with PLL frequency synthesis. The operation of the RF-3100 is straightforward; the good performance and the simple operation make the set, which is still occasionally available second-hand, a good entry-level receiver.
- DR-31 / RF-3100L: European version, incl. longwave coverage
- RF-3100LBE: British version with IF 10'702 / 462 kHz.
- RF-3100: USA - version
- 371 x 122 x 241 mm, weight 3.2 kg
The RF-3100 is designed as a travel receiver. With all the controls on the front panel, it looks like a small tabletop receiver and can also be used as such. With its dimensions of 37.1 x 12.2 x 24.1 cm and its weight of 3.2 kg, it is too bulky to be actually used as a travel radio. When the set was introduced in 1982, the criterion for travel use was whether the radio could be stowed under an aircraft seat. In any case, the RF-3100 can be operated from 110-125 / 220-240 V mains power or also 8 UM-1 batteries. The mains cable can be stored in a small compartment at the rear of the set. On the battery compartment cover on the top of the receiver, a band allocation and time zone plan is printed. The set can be set up for easier operation with a folding bracket, and a carrying strap can be attached at side eyelets.
The left quarter of the front panel is occupied by the 9 cm loudspeaker. In the corresponding right-hand quarter of the front panel the tuning knob is located, it has almost the same size and is equipped with a finger recess; the power switch is located at the top right.
In the centre of the front panel, the rotary switch, which in the European model is used to select FM, LW, MW and the 29 MHz ranges, is located at the right. The blue-green fluorescent display indicating the operation frequency with an accuracy of 1 kHz, the red operation LED, which becomes darker when the (battery) voltage fails are located in the middle, and to the left the quite sensitive field strengthmeter, which is calibrated in S-units und tends to read high. Below the frequency display are the switches for the S-meter illumination, the wide or narrow IF bandwidth filter and the BFO which is used to receive single-sideband transmissions. In the row below you find the headphones jack, the volume control, a double potentiometer for separate treble/bass tone control, the RF gain control, which regulates the radio frequency gain and which can be used to attenuate a signal in case of overload, and finally the BFO control. With these ten controls, including the power switch, the RF-3100 is straightforward to operate. On the are are three terminals for a long-wire and dipole antenna and a switch for the internal telescopic antenna. The DIN audio jack can be used to feed a signal to a tape recorder or to feed an audio signal to the receiver for amplification.
In practical use, short-wave reception with the RF-3100 is easy: Press the power switch, the red LED lights up and you will hear a hiss from the speaker. The band segment rotary switch is used to set the MHz digit on shortwave, e.g. 6. The other digits are set with the tuning knob; at 155, RÖI Vienna sounds from the loudspeaker on frequency 6155 kHz. The RF-3100 does not tolerate really long wire antennas too well, especially in the densely occupied 49 m, 31 m, 25 m bands at nighttime, the signal must be attenuated by using the RF gain control to avoid overloading, otherwise the desired signal gets lost in a mix of strong transmitters. The two IF filters both both have not very steep filter skirts, but they are well dimensioned for practical use; the narrow filter separates well in the 5 kHz channel spacing. SSB reception is possible with the BFO, but not very comfortable and due to some receiver drift, which according to the specifications should be belows 500 Hz per hour after warming up - according to my practical experience, however, the receiver sometimes has to be retuned 2 - 4 kHz in an hour. Due to the age and concept of the receiver, it lacks memory and clock functions.
If you looking just for a performing shortwave and FM receiver, the price-performance ratio of the receiver on the second-hand market is often good.
Double conversion; PLL frequency synthesis.
The set is equipped with semiconductors.