Manufactured by National Panasonic, Osaka.
In the mid-seventies, Matsushita - Panasonic tried to counteracted the dominance of Sony and Grundig world band receivers and launched a series of sucessful world band receivers, which allowed an unproblematic entry into shortwave reception at an attractive price tag.
Some of the circuits of these sets were probably also used in no-name sets from the Matsushita group, the Sanwa / Miramo 6090 is suspiciously reminiscent of the Panasonic sets with its technical features and the design of the switching elements. - I could recognise a similar arrangement in the Pan Crusaders and similar sets from other brands.
The DR-22 / RF-2200 is a 32 x 19.5 x 10 cm wide portable receiver. The double conversion superhet has tuning based on a vertically moves coarse dial, an calibrated fine tuning dial and a crystal calibrator to determine the operation frequency.
With a weight of 3.2 kg, the portable receiver was in its time comparatively light. A carrying strap could be attached to the top of the set, and there is a rotatable ferrite medium-wave antenna on top of the set, an advantage, since the set does not have to be rotated for medium-wave reception; similar features were found on other receivers from Japan in the 1970s.
The left part of the front panel is dominated by the loudspeaker grill, on top are the main switch and the switches for the dial illumination and the BFO.
On the right-hand side of the front panel are the display elements, on the left-hand side is the S-meter, which is an analogue instrument calibrated in S-units, next to it in the midle is the film dial moved vertically behind the pointer line with the coarse dials for VHF, shortwaves and mediumwaves. A red dot indicates the corresponding dial depending on the position of the band selector. Below the coarse frequency dial is the circular fine tuning dial with 0 - 1000 subdivision. This dial can be calibrated with the crystal calibrator and thus a frequency accuracy of around 10 kHz is possible. The tuning knob has a finger recess, and a switch at the left toggles between fast and slow tuning speed typical for Panasonic sets.
To the left below the S-meter are the switches for the wide and narrow AM IF filters, in FM mode the AFC can be switched off, next to it the switches for the 125 and 500 kHz signals of the crystal calibrator. Below this the rotary controls for volume and the separate treble and bass controls are located.
To the right of the tuning knob, one above the other, the shortwave range switch, the VHF - SW - AM (mediumwaves) switch and the RF gain control can be found.
On the left face of the set, there are jacks for earphone and cassette recorder connection, on the back of the European version DR-22 is the mains voltage connector (main voltage can be set to 110 or 220 V) and two screw terminals to connect an external antenna and ground wire. As far as I know, the ferrite antenna cannot be switched off, but its rotatable position allows you to peak medium-wave stations or to block interfering stations if the ferrite antenna is rotated to a 90° angle to the direction of the incoming signal.
Searching stations with the DR-22 /RF-2200 is unproblematic: the telescopic antenna extended, the radio is set to a medium volume hiss and the RF gain control fully turned up. The band switch is used to select MW or FM broadcast band; in the SW position, a red marker below the coarse dial marks the selected shortwave band. When the main tuning control is turned, some shortwave stations are briefly audible, for a slow station search, the Panasonic radio has a slow tuning speed setting.
The task becomes somewhat more complex when a station on a known frequency should be tuned. For this you have to calibrate the film dial with the help of a crystal calibrator and then move to the correct frequency with the linear fine tuning dial:
The internal crystal calibrator generates a crystal calibration signal every 500 kHz. First, the next 500 kHz calibration point below the desired reception frequency (i.e. for reception of the ROI on 6155 kHz the mark 6000 kHz, for reception of 11805 kHz the mark 11,500 kHz) is tuned to. With the 500 kHz marker switch pressed, a strong whistle should be audible near the dial position. Now tune to „zero beat“ with the main tuning, i.e. turn slowly until the whistle becomes deeper and deeper and then disappears completely. The pointer of the S-meter must move to the left stop. The fine tuning dial remains at the 000 setting during this manoeuvre.
After switching off the calibration marker, the dial moves again and can be set to 155 kHz - et voilà: the Austrian Radio Programme should become audible on 6155 kHz. With the 125 kHz marker, calibration marks can be activated every 125 kHz to check the dial linearity, the receiver is muted.
A BFO is available for receiving CW (A1) signals and SSB transmissions. When its activated, a whistle is audible; with the tuning knob set to „slow“, the optimum pitch of the Morse code transmission can be set for CW signals. For SSB transmissions, the pitch must be varied until the speaker's voice sounds natural; ECSS reception (i.e. reception of a single sideband of a normal AM broadcast) is possible with difficulty, but usually lead to any further improvement with this receiver.
In case of adjacent channel interference, the bandwidth switch can be set to narrow, but both IF filters are not really narrow.
The receiver works as a Double conversion heterodyne. The RF signal from the telescopic or MW ferrite antenna is amplified, converted to the first IF in a first mixer and amplified again. In a second mixer the signal is converted to the second IF, here the bandwidth filters are active, the S-meter voltage is tapped and the signal is fed to the AM demodulator or the BFO/SSB demodulator. The crystal calibrator works with a 4 MHz crystal and 1/4 or 1/8 dividers. In the FM range, the DR-22 / RF-2200 operates as a single conversion set.
In terms of reception, the set reflects the technology of the late seventies: reception on mediumwave is good, but in the FM broadcast band, the adjacent channel separation is insufficient by Central European standards; in America with a less dense FM network, this is usually no problem.
On shortwaves, the receiver concept with the built-in crystal calibrator and the calibrated fine tuning dial results in a quite good return accuracy and thus the capability to find a station on a known frequency, what usually was quite difficult with the German receiver concepts in those years (a dial on the turret tuner for each shortwave band, a quite wide dial pointer and only sparse coarse frequency marks).
Double conversion set, calibrated fine tuning dial and crystal calibrator.
The set is equipped with semiconductors.