SONY ST-JX8
¥ 70,000 (released in 1981)
Commentary
Based on the know-how of the ST-J75, which raised the quality of the synthesizer tuner by gathering Sony's IC technology, the circuit and material were re-examined and the synthesizer tuner aimed at higher perfection.
A direct comparator using Sony's original high-speed PLL IC is used.
This circuit employs a high-speed PLL IC that can directly divide frequencies up to the ultra-high frequency of 220 MHz. The comparison frequency from the crystal is set at 100 kHz, which is the same as the reception step. As a result, the comparison frequency is shifted to a band far away from the main signal and 38 kHz sub signal of the stereo signal, and noise and beat are greatly reduced.
In addition, in order to further improve the quality of wide-band ratio detection, a dedicated detection driver IC is adopted. By connecting this output directly to a DC composite amplifier with a wide dynamic range, the front and rear of the detection transformer are firmly suppressed, greatly contributing to the improvement of the SN ratio.
An FET buffer amplifier for impedance matching with the IF stage is mounted at the end of the front end. In addition, a uniphase filter of two elements and one package is used, and a differential limiter amplifier is inserted between stages to use four filters.
These 10-stage differential amplifiers provide excellent phase characteristics in the passband and rapid attenuation in the out-of-band region. These amplifiers greatly eliminate adjacent station interference while maintaining clear sound quality.
For the front end section, an all-FET configuration is adopted, such as 5-stage varicap, RF amplifier and mixer using dual gate MOS-FET, with special emphasis on RF intermodulation interference.
This eliminates non-linearity and provides stable reception performance against strong electric field input and spurious interference.
The MPX section employs a PLL-MPX ・ IC with a built-in pilot cancellation circuit that largely eliminates the pilot signal.
In addition, a 3-pole linear phase filter is adopted to eliminate unwanted signals of 15 kHz or higher to achieve low distortion and high separation.
It also uses a high-slew rate DC amplifier and a stabilized power supply.
Equipped with a 3-stage high / low / off muting level switching switch.
The muting level can be divided into two steps : High where the stereo broadcast transmission is almost practical, and Low where it is almost practical if it is made into a thing. In addition, when it is turned off, an FM blend circuit is automatically activated, and the SENS mechanism is installed to improve the acoustic sensitivity.
The AM tuner section uses a notch filter that greatly reduces beat noise.
The AMIF and AF bands can be switched to three levels : Distant, Normal, and Local. The SENS mechanism is activated when the AMIF and AF bands are set to Muting-off (when the display is Distant). Not only the high band but also the low band can be cut to improve the actual sensitivity.
It is equipped with FM/AM direct random 8 station preset using multi-process memory. It can preset up to 8 stations at any position regardless of FM/AM. In addition, each station can record settings such as FM/AM band, muting, SENS, and FM mode. You can call up the desired station while keeping the optimum reception condition with one touch.
In addition to this direct random tuning system, we have adopted a 4-speed tuning system consisting of a quick search (auto) that automatically selects neighboring stations, a sweep tune (manual) that changes frequency slowly, and a step tune (manual) that changes in FM100kHz and AM9kHz steps per one touch.
Equipped with a timer compatible 8-station program memory, it is possible to recall up to 8 specified preset stations one after another in order in conjunction with ON/OFF of the power switch.
This allows you to easily record between two or more stations using a program timer.
It is also equipped with a memory scan function to easily check the programmed station and order, and NEXT CALL to check the station to be called when the switch is turned on next time.
The memory IC uses Sony's proprietary non-volatile memory IC that does not require any backup power supply and retains the memory contents semi-permanently.
Even in the event of a power failure, there is no need to worry about the memory being released, and you can use it safely to record your absence with a weekly timer.
Equipped with a CAL-TONE switch that is convenient for adjusting the air check level.
Equipped with 5-step LED signal indicator with strong electric field display.
FM antenna terminal with F-type plug for 75 Ω coaxial cable is seen through.
A 300 Ω feeder antenna can be used by the included adapter (EAD-25).
Equipped with Last One Memory that recalls the station you were listening to when you turned off the power when you turned the power on.
7-segment digital display is adopted.
In order to emphasize sound quality, a copper-plated case and oxygen-free copper power cord with polarity display are used.
The audio amplifier uses a 2-power supply system with FET buffer.
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Model Rating
| Type | Quartz-lock digital frequency synthesizer tuner | ||||
| Circuit system | PLL digital frequency synthesizer Quartz lock system Superheterodyne FM/AM Tuner |
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| FM Tuner Section | |||||
| Receiving frequency | 76 MHz to 90 MHz | ||||
| Antenna terminal | 75 Ω F Type Stopper | ||||
| Intermediate frequency | 10.7MHz | ||||
| SN ratio 50 dB sensitivity | Mono : 3.8 μ V (IHF) / 16.8 dBf (new IHF) Stereo : 40 μ V (IHF) / 37.3 dBf (new IHF) |
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| Practical sensitivity | 1.8 μ V (IHF) / 10.3 dBf (new IHF) | ||||
| Signal-to-noise ratio | mono:92dB stereo:86dB |
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| Harmonic distortion factor |
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| Cross modulation distortion factor | mono:0.05% stereo:0.06% |
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| Stereo separation | 50dB(100Hz) 60dB(1kHz) 45dB(10kHz) |
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| Frequency characteristic | 30 Hz to 15 kHz ± 0.2 dB | ||||
| Effective selectivity | 90dB(400kHz) 60dB(300kHz) |
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| Capture ratio | 1.0dB | ||||
| AM suppression ratio | 65dB | ||||
| Image interference ratio | 120dB | ||||
| IF interference ratio | 120dB | ||||
| Spurious interference ratio | 120dB | ||||
| RF intermodulation interference ratio | 88dB(IHF) 105dB(2.4MHz) |
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| Carrier leak suppression ratio | 78dB | ||||
| Muting level | 25 dBf, 10 μ V | ||||
| Auto-tuning level | 25dBf | ||||
| Output Level / Impedance | 750mV/600 Ω | ||||
| <AM Tuner Section> | |||||
| Receiving frequency | 522 kHz to 1602 kHz | ||||
| Antenna | Ferrite bar antenna with EXT terminal | ||||
| Intermediate frequency | 450kHz | ||||
| Sensitivity | 200 μ V/m (when bar antenna is used) | ||||
| Signal-to-noise ratio | 55dB(50mV/m) | ||||
| Harmonic distortion factor | 0.3% | ||||
| Frequency characteristic | 30 Hz to 6 kHz -3dB | ||||
| Selectivity | 45dB(9kHz) | ||||
| Image interference ratio | 45dB | ||||
| Auto-tuning level | 500 μ V/m | ||||
| <General> | |||||
| Power supply voltage | 100 VAC, 50Hz/60Hz | ||||
| Power consumption | 18W | ||||
| External dimensions | Width 430x Height 80x Depth 330 mm | ||||
| Weight | 4.6kg | ||||
| Attachment | Antenna Connector EAD-25 (300 Ω → 75 Ω conversion) Feeder antenna F-type plug Connection code Station Name Label (Set) |
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