Unterschiede

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--- en:nrd-535 [2021/12/27 09:57] – [Technical data] mb
+++ en:nrd-535 [2021/12/27 13:26] (aktuell) – mb
@@ Zeile 15: / Zeile 15: @@
   * [[Features]]: Scan - Functions, Clock / Timer, RS-232 - Interface
   * [[Sensitivity]]: 100 kHz - 500 kHz [[AM]] <15.8 μV, [[SSB]] <5 μV;
-  * 500 kHz - 1.6 MHz [[AM]] <6.3 μV, [[SSB]] <2 μV;
+  * [[Sensitivity]]: 500 kHz - 1.6 MHz [[AM]] <6.3 μV, [[SSB]] <2 μV;
-  * 1.6 - 30 MHz [[AM]] <2 μV, [[SSB]] <0.32 μV, [[FM]] <0.5 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).
@@ Zeile 38: / Zeile 38: @@
 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 activity of the noise suppressor. 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 as a warning with a small red glowing note (ATT, PBS, NOTCH, etc.). The fact that there are no double potentiometers or double function assignments for these rotary controls also contributes greatly to the clarity of the unit. Six buttons in a slightly slanted bar below the display allow direct access to the various Operation modes. Via a double 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 alternatively show the reception frequency to an accuracy of 10 Hz, or the time, but both are not available at the same time. The display of the memory space has turned out much smaller, even smaller are the marks 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.
+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.
+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.
-The RS-232 computer interface is fitted as standard on the NRD-535, and the RTTY decoder board familiar from its predecessor can also be plugged into this receiver as an option for receiving radioteletype transmissions. However, the NRD-535 can no longer be operated with an internal VHF/UHF converter.
+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 input sensitivity in the short-wave range and large-signal immunity, which is at least equal to its predecessors. The occurrence of "ghost stations" as a result of internal mixed products is a rarity thanks to the automatic preselection and the high-positioned 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 NF noise 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 increases strongly as a result of this manoeuvre, since the signal no longer fluctuates so strongly with the fading of the carrier signal - is problem-free, the circuit engages reliably. However, it should be operated with caution when additionally tweaking the signal with PBS and BWC; if the receiver loses synchronisation, there will be a howl.
+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 NRD-535 is equally suitable for broadcast DX, especially with 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 was beaten to 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 "marking up" with regard to the price.
+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.
-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 with a terminal programme. I use the programme Smart NRD Control by Mark Fine to control the receiver, with which a station from the frequency database sounds out of the NRD at the click of a mouse. The only thing that spoils the fun is PC-related HF interference, which can affect very weak signals - for proper DXing I sit down directly at the receiver.
+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 running preselector opens the path only for signals from the set frequency range. After an amplifier stage, the conversion to the high first intermediate frequency of 70.455 MHz takes place, after further amplification to the second IF of 455 kHz. The noise blanker, which helps to eliminate unwanted clicks and pops, also works 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 using the inter-filter. After a further conversion to the third intermediate frequency of 97 kHz - here the HF emergency filter is used to suppress interfering whistling tones from neighbouring carrier signals, the passband tuning is used to shift the filter passband curve and thus eliminate an interfering neighbouring channel transmitter, and the synchronous detector is used for automatic ECSS reception - the signal that has been cleaned several times in this way 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 (in a tuning range of 30 MHz).
+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 ====