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====== JRC NRD-535 ======
Manufactured by [[Japan Radio Co.]], Tokyo.

5 years after the introduction of the extremely successful station receiver [[NRD-525]], the Japanese manufacturer [[JRC]], which got an excellent reputation in the field of amateur and maritime radio, introduced a successor, the **NRD-535**, which featured as most important innovations a continuously variable bandwidth control and a synchronous demodulator for automatic [[ECSS]] reception. It should be noted that there are different versions of the receiver, only the NRD-535DG (European version) or 535D (US version, with golden lettering) is equipped with the ECSS board, the BWC board and the narrow 1 kHz IF filter. In the early sets up to serial no. 56005, the variable bandwidth control BWC was only active with the INTER filter in SSB mode.

{{:images:jrc-nrd535.jpg?600|JRC NRD-535}}
===== Technical data =====
  * [[Principle]]: [[triple conversion superhet]], [[IF]] 70.455 MHz, 455 kHz, 97 kHz.
  * [[Operation modes]]: [[A1]], [[SSB]], [[A3|AM (A3)]], [[AM sync.]], [[F3|FM-n (F3)]]
  * [[Frequency range]]: 100 kHz - 30 MHz
  * [[Frequency display]]: [[digital display]], 10 Hz
  * [[Frequency memory]]: 200 memories
  * [[Signal strength indicator]]: [[S-meter]]
  * [[Signal processing]]: [[RF gain]], [[AGC]] x 3, [[PBT]], [[noise blanker]], [[notch filter]]
  * [[Features]]: Scan - Functions, Clock / Timer, RS-232 - Interface
  * [[Sensitivity]]: 100 kHz - 500 kHz [[AM]] <15.8 μV, [[SSB]] <5 μV;
  * [[Sensitivity]]: 500 kHz - 1.6 MHz [[AM]] <6.3 μV, [[SSB]] <2 μV;
  * [[Sensitivity]]: 1.6 - 30 MHz [[AM]] <2 μV, [[SSB]] <0.32 μV, [[FM]] <0.5 μV
  * [[Selectivity]]: AM wide 6/15 kHz, inter 2/6 kHz, narrow* 1/3 kHz, aux/FM 12 kHz & variable bandwidth (-6/-60 dB).

==== Power supply ====
  * [[Mains operation]]: 110, 220 V AC
  * Battery operation: 12 - 16 V DC from an external power source

==== Dimensions ====
  * 330 x 130 x 287 mm, weight 9 kg

==== Accessories ====
  * **NVA-88** loudspeaker resp. **NVA-319** loudspeaker with integrated NF filter

===== Operation =====
In terms of its dimensions (33 x 13 x 28.7 cm, 9 kg), the NRD-535 is similar to its predecessors; the anthracite-grey housing colour and the layout of the front panel with the gas fluorescent display behind the red-brown plastic cover have also been retained; the design has been adapted to the 1990s with softer shapes of the controls and rounded keys.

The receiver can be powered in station mode with 100 - 240 V mains current or alternatively with 12 - 16 V DC voltage, for example from a car battery.

A monitor speaker is located under a grill in the upper housing cover, which can at least be used to check whether the radio is really "playing"; for serious listening, an external speaker must be connected. Besides the NVA-88 (actually belonging to the NRD-525), JRC offers the expensive NVA-319 loudspeaker equipped with an LF filter.

The arrangement of the controls on the **front panel** has been slightly changed. The three-position mains switch with a position for activating the timer mode has been moved to the left, the volume control and the tone control are on the right below the number keys. The numeric keys for direct frequency entry are still located on the front of the unit in an upright position; after longer operation with frequent frequency entries, one risks the typical NRD wrist cramp (the numeric keys of the Drake R-8 are located further down, here only the character of the wrist pain changes...). The six buttons above the main tuning knob change the function of the big UP/DOWN buttons. Depending on the setting, which is marked by a small LED, these buttons change the frequency, bandwidth, AGC response speed, tuning step width and speed, call up the memories or activate ECSS operation.

Six easy-to-grip rotary controls to the left of the large main tuning knob, which is also pleasantly smooth on this receiver, are used to set the RF gain, the [[notch|notch filter]] to suppress an unwanted interference signal, the squelch, the [[PBT|passband tuning]], the adjustable bandwidth (BWC) and the noise limiter. JRC has reacted to the fact that incorrect operation of these controls by newcomers to shortwave reception sometimes made reception impossible, so the activation of each function is indicated in the display with a small red indicator (ATT, PBS, NOTCH, etc.). The fact that there are no concentric double controls or double function assignments for these rotary controls also contributes to a straightforward operation. Six buttons below the display give direct access to the different operation modes. Via a secondary function, the less frequently used timer and scan functions and the attenuator can be called up with the same keys. The S-meter is still a coloured bar that jerks up and down nervously, and the large, easy-to-read digits display the reception frequency with an accuracy of 10 Hz, or alternatively the time, but both are not available at the same time. The display of the memory channel has turned out much smaller, even smaller are the indicators for the activated operation mode, bandwidth, AGC speed and the operating states of the special functions mentioned above. At least it can be assumed that if on an unused frequency the S-meter bar is on the far left and no red mark lights up, the NRD-535 is in a normal operating state, the background noise should now become audible.

The rear panel is similar to that of the [[NRD-525]], only the missing VHF/UHF antenna connectors and the model designation NRD-535 indicate which receiver you are sitting behind. The antenna input can be switched from a high-impedance long-wire antenna to a coax input.

An RS-232 computer interface is fitted as standard on the NRD-535, and the same RTTY decoder board as found on the predecessor can also be plugged into the NRD-535 as an option to receive radioteletype transmissions. However, the NRD-535 can no longer be operated with an internal VHF/UHF converter.

In practical use, the NRD-535 is characterised by its high sensitivity in the short-wave range and rugged large-signal behaviour, which is at least equal to its predecessors. The occurrence of "ghost signals" as a result of internal mixed products is a rarity thanks to the automatic preselection and the high first IF. Thanks to its high sensitivity, the NRD-535 provides good reception results even on improvised wire antennas and does not have to surrender due to overloading on a really long long-wire antenna.

The possibilities to eliminate interfering signals are very good thanks to [[passband tuning]] and adjustable IF bandwidth, the quality especially of the wider IF filters was criticised in the early sets. The trimming of the bandwidth by the BWC doesn't seem so steep to me, in narrow positions the sound tends to be more muffled than with the Collins [[R-390A]] in the 4 or 2 kHz bandwidth. The audio hiss of the NRD-535 has been reduced considerably compared to its predecessor, and the fact that the receiver is so quiet takes some getting used to at the beginning. The ECSS mode with selectable sideband - in this automated SSB mode a carrier signal generated in the receiver is mixed with the received sideband information, the intelligibility of a signal increases significantly as a result of this manoeuvre, since the signal does not longer fluctuate heavily with the fading of the carrier signal - is problem-free, the circuit locks reliably. However, it should be operated with caution if the signal is additionally tweaked with PBS and BWC; if the receiver loses synchronisation, there will be a howl.

The NRD-535 is equally suitable for broadcast DX, especially when listening to weak signals and signals affected by interference, as well as excellent for receiving CW or radio teletype signals for the utility DXer. Quickly after its release, the NRD-535 became the reference receiver of most testers before the successor [[NRD-545]] and the Watkins Johnson [[HF-1000]] with digital ([[DSP]]) signal processing took the stage. As always after the release of its successor, the NRD-535 can provide top-class reception at a very good price-performance ratio when purchased as a second-hand set. However, before buying a second-hand NRD-535, it is important to check whether the set is really equipped with the desired options. If not, it is either a case of doing without, of expensive retrofitting (the installation of the optional boards is described in the manual) or of bargaining for a better price.

After I had soldered a suitable serial PC cable, my PC made contact with the NRD-535 without any problems when the pin assignment of the cable was finally correct. With the well-documented control sequences in the manual, the receiver can be addressed from a terminal programme. I use the programme Smart NRD Control by Mark Fine to control the receiver, in which a station can be called up from the frequency database at the click of the mouse. The only thing that spoils the fun is PC-related HF interference, which can affect very weak signals - for proper DXing I tune the receiver directly.

===== Technical principle =====
The HF signal first passes through a 35 MHz low-pass filter and the switchable 20 dB attenuator, then the electronically tuned preselector opens the path only for signals around the set frequency. After an amplifier stage, the conversion to the high first intermediate frequency of 70.455 MHz takes place, after further amplification it is converted to the second IF of 455 kHz. The noise blanker, which helps to eliminate unwanted clicks and pops, is active at this level. After the switchable [[IF filters]], the IF bandwidth can be reduced electronically with the bandwidth control circuit from 2.4 to 0.5 kHz, when the INTER-filter is in use. After a further conversion to the third intermediate frequency of 97 kHz - here the Notch filter can be used to suppress an interfering whistle from an adjacent channel signal, the [[passband tuning]] is used to shift the IF filter passband curve and thus eliminate an interfering adjacent channel signal, and the synchronous detector is used for automatic [[ECSS]] reception - the signal is demodulated and, depending on the squelch setting, fed to the loudspeaker and the ear of the inclined listener. The oscillator frequencies are processed by a very low-noise DDS-PLL synthesiser with an accuracy of 1 Hz.

==== Components ====
The set is solid state.

===== Technical documentation =====
  * {{ :manuals:jrc-nrd-535-operating-instructions.pdf |Operating Instructions; e}}

==== Development ====
{{gallery>:images?jrc-nrd535*.jpg&0&80x80&lightbox&showtitle&titlesort}}
==== Further information ====
  * [[https://www.radiomuseum.org/r/jrc_nrd_535.html|JRC NRD-535 on the website of www.radiomuseum.org]]