Lo-D FT-620
¥ 55,000 (around 1976)
Commentary
AM/FM stereo tuner with sensor auto-lock tuning mechanism.
The front end is equipped with a 4-row frequency number line type varicon and a low-noise dual-gate MOS FET sensitivity.
The IF amplifier circuit uses four stage differential amplification by IC and three ceramic filter elements with excellent phase characteristics to provide high level limiter characteristics and high selectivity.
In addition, wide-band quadrature detection is adopted in the detection stage to realize low distortion and improve the capture ratio.
It is equipped with a sensor, auto-lock and tuning mechanism to accurately maintain the best receiving point.
This auto-lock mechanism catches radio waves at the best reception point, and once radio waves are received, it can always maintain the reception frequency. In addition, it can receive and maintain various characteristics such as distortion and separation in the best condition and stably.
This is due to the automatic control function of the IC. During this automatic lock, the dial indicator lights in red to indicate that the best point has been received and that stability has been maintained.
If the tuning knob is touched during tuning, the auto-lock mechanism will be released and manual tuning can be performed using the center tuning meter.
The MPX circuit uses a PLL (Phase Locked Loop) circuit based on ICHA 1156.
It is equipped with muting circuit by lead relay and IC.
The AM tuner section is designed to reduce noise.
It is equipped with an MPX noise filter, FM multipath terminal and band indicator.
Each AM/FM has a level adjustment mechanism.
Equipped with 4-ch out terminal.
The wood case in the picture was sold as an optional item sold separately.
Model Rating
| Type | FM/AM Tuner | ||||
| FM Tuner Section | |||||
| Circuit system | RF 1st stage using dual gate MOS FET 4-stage variable capacitor 4-stage differential IF amplifier Ultra Wideband Linear Detector PLL MPX |
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| Practical sensitivity | 1.6 μ v (IHF) 3.0 μ V (S/N 50 db, mono) 40 μ V (S/N 50 dB, stereo) |
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| S/N | mono:73dB Stereo : 68 dB (13.6 kHz with LPF) |
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| Harmonic distortion factor |
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| Capture ratio | 1.0dB | ||||
| Effective selectivity | 80dB | ||||
| Frequency characteristic | 20 Hz to 15 kHz + 0.2 -2dB | ||||
| Separation | 50dB(1kHz) 38 dB (50 Hz to 10 kHz) |
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| Image interference ratio | 85 dB or more | ||||
| IF interference ratio | 90 dB or more | ||||
| Spurious interference ratio | 100dB | ||||
| AM suppression ratio | 52dB | ||||
| Carrier leak suppression ratio | 65dB | ||||
| Muting action level | 24dB | ||||
| Antenna | 300 Ω Balanced Type, 75 Ω Unbalanced Type | ||||
| <AM Tuner Section> | |||||
| Circuit system | Tuned RF1-stage, 3-series Varicon | ||||
| Practical sensitivity | 18 μ V (IHF) 300 μ V/m (bar antenna) |
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| Selectivity | 40dB | ||||
| S/N | 50dB | ||||
| Image interference ratio | 65 dB or more | ||||
| IF interference ratio | 85 dB or more | ||||
| <General> | |||||
| Output Level / Impedance | Fixed : 0.65V/6k Ω or less Variable : 0.04 V ~ 1.2V/1k Ω or Less 4 ch out : 0.2V/1k Ω or less |
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| Semiconductor used | Transistor : 24 FET : 1 IC : 4 Diode : 25 pcs |
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| Power supply voltage | 100 VAC, 50Hz/60Hz | ||||
| AC outlet | Power switch not linked : 1 system | ||||
| Rated power consumption (Electrical Appliance and Material Control Law) | 19W | ||||
| External dimensions | Body : Width 435x Height 144x Depth 394 mm Wood Case : Width 467x Height 179x Depth 400 mm |
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| Weight | 7.8kg | ||||
| Sold Separately | Wood Case LA-200 (¥ 6,500) | ||||