Manufactured by Japan Radio Co., Tokyo.
After the predecessor model, the all wave receiver NRD-515 had already given the Japanese manufacturer Japan Radio Co. an excellent reputation, the NRD-525 improved the companys reputation. The NRD-525 which was built in larger numbers, was widely used by shortwave listeners and is still frequently offered on the second-hand market.
With its dimensions of 33 x 13 x 28 cm and a weight of 8.5 kg, the NRD-525 is roughly the same size as its predecessor, but with the same dimensions, a small monitor speaker is already built in and the memory unit standing on top of the receiver can also be omitted. In the seven years since the appearance of the NRD-515, the front panel design has been adapted to technical and fashion developments. With its anthracite coloured front panel, the multi-coloured fluorescent display and the grey, orange, white and blue coloured push-buttons, the NRD-525 no longer looks quite as venerable and professional as its predecessor.
After removing the unit's cover, the fully modular construction with several printed circuit boards becomes visible. For repairs and modifications, entire boards can be exchanged or optional modules such as the RTTY demodulator, a PC control board with an RS-232 interface or the VHF/UHF converter can be plugged in.
The external loudspeaker NVA-88 helps the set to a really good audio reproduction.
The translation of the operating instructions is somewhat uninspired, but there is a description of how to install the options and detailed circuit diagrams. More detailed information can be found in the service manual, which could be ordered from IRC for an additional charge. Not only with the NRD-525, but also with other high-quality communications receivers with their multitude of controls, beginners may be disappointed if, due to incorrect setting of RF gain, PBT or notch filter, the audio signal from the speaker is hardly intelligible due to the control possibilities of the receiver. Warning lights or detented centre positions for the aforementioned controls, which could prevent incorrect manipulations, are missing. However, if the NRD-525 does not produce the same audio as another receiver, it is worthwhile to adjust all controls to their basic position described in the manual. The Swiss Army e.g. improved the usability with small yellow colour points marking the standard settings.
In contrast to the British company Lowe, for example, JRC follows a different operating philosophy - so that all functions can be accessed directly from the front panel with separate buttons and controls. So you end up with no less than 43 controls on the front panel. At the bottom right is the power switch with a position for timer operation and next to it the volume control „AF-Gain“.
Above the numbered keypad, there are two keys to select direct frequency entry tuning FREQ or to memory recall operation „CHANNEL“. Depending on the setting, a frequency in MHz or kHz can be entered using the numeric keypad - unfortunately a dot marking key 5, which would be helpful for DXers with poor eyesight, is missing - and the receiver can be tuned with Enter. Alternatively in CHANNEL mode, a memory channel number can be entered and accessed with the Enter key. According to the setting, the UP-Down keys can be used for quick frequency tuning or for quickly searching the stored frequencies. The other buttons above the main tuning knob select the operation modes and the filter bandwidths. Unfortunately, there are no buttons to directly access a desired operation mode or filter as found on the Drake R-8A (but not on the Drake R-8, even Frake had to learn a lesson).
At the bottom left, there are 7 easy-to-grip rotary knobs, fortunately there are no double controls that need to be operated with small fingers. The radio frequency gain RF-Gain can be adjusted with the knob next to the main tuning knob, the other knobs adjust the BFO, the passband tuning to shift the IF filter passband, the notch filter working at IF level to suppress a whistle from an interfering signal, the squelch function and the tone control. You can adjust the width and intensity of the Noise limiter.
The dimmable fluorescent display behind an aubergine-coloured transparent cover provides multicoloured information about the operation frequency (accuracy up to 100 Hz), memory channel number and several operation states. The S-meter is designed as a fluorescent bar and reacts much more „nervous“ then its mechanical counterpart. The clock function can only be called up by pressing a button; when the frequency is displayed, the time disappears again. Other small buttons below the display activate a frequency offset (RIT), the attenuator and the AGC speed, as well as the frequency scan (SWEEP) and the memory scan (SCAN) functions. In SWEEP mode, a frequency range between two corner frequencies is scanned by the receiver, the scanning speed is set with the PBS/SPEED control, the response threshold with the SQUELCH control. The RUN button starts the scan.
The earliest NRD-525s had only one tuning speed, with 2 kHz per turn of the tuning knob and a smallest step size of 10 Hz, the receiver was perfect for utility (radioteletype/fax) reception, but scanning through a broadcast band could end up with tendon problems because so many rotations were necessary. In later sets (after late 1986), the tuning speed can be increased tenfold with the RUN key and the tuning step can be set to 100 Hz, the step width of the up/down keys thus is increased from 1 to 10 kHz. It is also worth mentioning that various features (display of the 10 Hz digit in the frequency display, confirmation beep after each keystroke and a bypass of the input RF filter stage to increase the input sensitivity while accepting a worse intermodulation behaviour) can be called up by key combinations, so that the receivers characteristiscs can be adapted to the user.
The rear panel provides all necessary input and output sockets. In addition to various mains voltages, the NRD-525 can be powered from 13.8 V DC in a field day, low-power timer connectors ae activated by the built-in timer, I switched mains power over it using a relay and was thus able to use my cassette recorder for unattended recording. Two antenna sockets for long-wire and low-impedance coaxial antennas are switchable; depending on the built-in options, the PC or a printer can be connected to the RTTY decoder.
In everyday use, the NRD-525 excels with its excellent sensitivity and the possibilities of RF signal post-processing. It allows successful DX experiences even with moderately long wire antennas. Thanks to the electronic preselection, I never had problems with „ghost signals“ as a result of undesired mixing products. The WIDE filter with a width of 4/10 kHz can loead to interference from the adjacent 5 kHz channel, the INTER filter leads to a muffled sound in AM reception, for broadcast station reception I would have preferred a steep 4 kHz filter. With the passband tuning and the notch filter, I was usually able to eliminate such interference, but the PBT of my Icom R-70, modified for AM reception, cuts away interfering signals more sharply. The synchronous detector in AM mode does not allow sideband selection and cannot be compared to the synchronous demodulator of the Sony ICF-2001D, the AR7030 or the ECSS mode of the successor model NRD-535. For utility station reception, the NRD-525 is very suitable thanks to the two narrow IF filters, the small tuning steps and the memory options. According to reports, the fluorescent display can cause RF interference from small receivers or MW loop antennas operated in the vicinity.
What comes out of the radio has always been the subject of long discussions, which I do not want to revive here. It is clear that the sound from the built-in „monitor“ loudspeaker is beyond good and evil and that the use of an external 4 Ohm loudspeaker or headphones is indispensable. The noise floor is considerable, and because of this and the musty sound, especially with the medium AM filter, long hours of radio listening is somewhat tedious. The Collins R-390 with its mechanical filters simply delivers more pleasant audio in AM - but as an extremely versatile receiver, from mediumwaves, tropical band DX to utility station reception with radioteletype decoding, the NRD-525 remained unbeaten for a long time and is still a very serious DX receiver today.
After the attenuator, the radio frequency signal has to pass through an electronic preselector stage with capacitance diodes. After a 35 MHz low-pass filter and an amplifier stage, the signal is converted to 70.455 MHz in the first mixer. After an IF amplifier, it is converted in the second mixer to generate the 2nd IF of 455 kHz. This is followed by the noise limiter and the IF filter bank. After the IF notch filter, the BFO signal for CW reception and demodulation is done.
The frequency processing is done in a PLL synthesis circuit with an accuracy of 10 Hz, the numerous memory and scan functions transmit their digital information to this component. Not only the frequency, but also the operation mode, bandwidth, attenuator and AGC status are stored in the two hundred memory locations.
The set is solid state.