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FT-420
Commentary

An AM/FM stereo tuner announced as a high-cost performance tuner with stable reception and high fidelity reproduction.

The front-end uses a frequency linear four link varicon, combined with a low-noise MOS FET to achieve excellent sensitivity and interference rejection.

In the intermediate frequency amplifier stage, four stage differential amplification by IC and three ceramic filter elements with excellent phase characteristics are adopted, and excellent limiter characteristics and interference removal effect are obtained.
In addition, IC-based quadrature detection realizes a wide bandwidth, low distortion, and an improved capture ratio.

Equipped with an auto-lock tuning mechanism.
With this function, when a radio wave is caught at the best reception point, the reception frequency is kept stable, so that distortion and separation can be received stably in the best condition.
This is achieved by the automatic control function of Hitachi's ICHA 1137.

The MPX circuit is equipped with a PLL circuit based on ICHA 1156 developed by Hitachi, and provides reception characteristics resistant to the influence of ambient temperature and changes over time.

A muting circuit is mounted to suppress inter-station noise and noise during detuning.
This circuit consists of a reed relay for communication equipment developed by Hitachi and a control circuit by IC.

The AM tuner section uses an untuned high-frequency amplifier circuit. The excellent selectivity of the ceramic filter and the AGC characteristic of the IC realizes reception that is resistant to interference and radio wave strength.
In addition, the use of an IC-type balanced mixer circuit improves spurious characteristics.

Uses a 2-meter signal tuning method.

There are two types of output terminals, fixed and variable.

It is equipped with FM multi-pass terminal and 4-channel out terminal.

There was a wood case as an option 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
Wideband linear detector PLL MPX
Practical sensitivity 1.7 μ V (IHF)
3.0 μ V (S/N 50 db, mono)
40 μ V (S/N 50 dB, stereo)
S/N mono:73dB
Stereo : 68 dB (13.6 kHz with LPF)
Harmonic distortion factor
mono: 0.2%(100Hz)
0.15%(1kHz)
0.2%(10kHz)
stereo: 0.3%(100Hz)
0.25%(1kHz)
0.5%(10kHz)
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)
Image interference ratio 85dB
IF interference ratio 90dB
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)
Selectivity 36dB
S/N 50dB
Image interference ratio 40dB
IF interference ratio 55dB
<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
Semiconductor used Transistor : 14
FET : 1
IC : 4
Diode : 21
Power supply voltage 100 VAC, 50Hz/60Hz
AC outlet Power switch not linked : 1 system
Rated power consumption (Electrical Appliance and Material Control Law) 18W
External dimensions Body : Width 435x Height 144x Depth 394 mm
Wood Case : Width 467x Height 179x Depth 400 mm
Weight 7.5kg
Sold Separately Wood Case LA-200 (¥ 6,500)