The first
requirement in an FM tuner that is designed to furnish high fidelity reception
is accurate tuning. If the tuning is off
just a bit, there is an increase in distortion and decrease in stereo
separation, two problems which can negative the virtues of even the best tuner
designs.
In the
ST-8044, the problem of inaccurate tuning was solved quite simply. First,
Technics designers removed all needle-type mechanical meters, which are usually
used to indicate signal strength and
center-of-channel tuning, and replaced them with responsive and easy-to-read
LED's . And once you've tuned in a
ststion, the active servo lock will keep it from drifting despite temperature
and humidity changes. In short, with the ST-8044, accurate tuning aids and the
servo lock contribute directly to low distortion and stable stereo separation.
Active Servo
Lock
One way to
prevent frequency drift and its accompanying distortion is to "lock"
the local oscilator. But with this approach, the IF stage and FM discriminator
cannot respond to temperature changes, which occur as the tuner "warms
up", and other varying conditions. However, the Active Servo Lock in this
tuner maintains precise, center-to-channel tuning under these conditions by
preventing frequency drift not only in the local oscilator but also in the IF
stage and FM discriminator. The big merit is that even a careless or hasty
setting of the dial is sufficient to tune in the station accurately with the
ST-8044. Where as you normally would have to
position the center-tuning meter rather carefully for low distortion and
good stereo separtion. with the active
servo lock you can tune within ±75 kh on either side of the station's
frequency. The active servo lock is then activated three seconds after the
tuning LED's light up, and at the same time the "Servo Lock"
indicator light goes on.
Just tune
the ST-8044 to the general area of the station and the active servo lock will
do the rest. If for any reason you want to defeat the servo lock, you can do so
by pressing a switch.
High-Sensitivity
Front End
The RF
stage benefits from, among other components, a junction FET for good
selectivity, sensitivity, image and spurious rejection. Tuning is accomplished
with a precision3-ganged variable tuning capacitor, and the figures tell the
story of the high-sensitivity of this tuner; usable sensitivity is 1,9 µV (300 Ω). The more important 46 dB stereo quieting
sensitivity is 2,5 µV (75 Ω).
High S/N
Ratio and Wide, Stable Separation
In the IF
stage, you'll find three flat-group-delay ceramic filters for high selectivity
and a five-stage differential amplifier with excellent limiting
characteristics. Selectivity is 75 dB; the S/N Ratio is 75 dB (IHF), and
separation is a wide 45 dB at 1 kHz, MPX decoding is accomplished with a PLL
(phase locked loop) circuit incorporated into a single IC.
5 LED's
Indicate Signal Strength
The number
of LED's lit indicate signal strength in a linear progression. One LED means
that the signal is very weak and is barely being picked up by the tuner. Two
LED'ss mean that the station is weak and the program material will be difficult
to hear. Three LED's ; the quality of the sound will not be very good, but
speech can be readily understood and music will be listenable. Four LED's ; the signal is strong enough for
good musical fidelity. Five LED's; strong signal, bets possible reception with
this tuner.
Other
Features
Quadrature
detector with outstanding characteristics contributing to a wide, flat
frequency response and low distortion.
Easy-to-read
220 mm dial scale. The tuning knob's "positive" feel is enhanced by
an oil-less sleeve and a dial rope coated with fluoro-resin.
Special
muting circuit to reduce pop noise when detuning.
Fm Auto/Mono
switch and FM muting to eliminate inter-station noise when tuning between
stations.
High-quality
AM section with 2-ganged variable capacitor and ceramic filter.
Specifications
FM Tuner
Section
Frequency
range: 88 - 108 MHz
Sensitivity:
S/N 30
dB : 1,9 µV (300 Ω); 1,3 µV (75 Ω)
S/N 26
dB : 1,7 µV (300 Ω); 1,2 µV (75 Ω)
S/N 20
dB : 1,5 µV (300 Ω); 0,9 µV (75 Ω)
IHF usable
Sensitivity: 1,9 µV (IHF '58)
IHF
S/N 46 dB Stereo Quieting Sensitivity:
25 µV (75 Ω)
Total
Harmonic Distortion (1 kHz): 0,15%
(mono); 0,3% (stereo)
Signal-to-Noise
Ratio:
Mono : 68 dB (75 dB, IHF)
Stereo
: 65 dB (70 dB, IHF)
Frequency
Response: 20 Hz - 15 kHz, +0,5 dB -1,5 dB
Alternate
Channel Selectivity: 75 dB
Capture
Ratio: 1,0 dB
Image
Rejection at 98 MHz: 55 dB
Spurious
response Rejection at 98 MHz: 80 dB
AM
Suppression: 55 dB
Stereo
Separation: 45 dB at 1 kHz; 35 dB at 10 kHz
Carrier
Leak:
19 kHz
: -35 dB (-40 dB, IHF)
38 kHz
: -48 dB (-40 dB, IHF)
Channel
Balance: 250 Hz - 6300 Hz ±1,5 dB
Limiting
Point: 1,2 µV
Bandwidth:
IF Amplifier
: 180 kHz
FM
Demodulator : 1000 kHz
Antenna
Terminals: 300 Ω (balanced), 75 Ω
(unbalanced)
AM Tuner
Section
Frequency
Range: 525 - 1605 kHz
Sensitivity
S/N 20 dB : 30 µV, 250 µV/m
Selectivity: 30 dB
Image
Rejection at 1000 kHz: 50 dB
IF Rejection
at 1000 kHz: 40 dB
General
Output
Voltage: 0,6 V (fixed)
Power
Consumption: 16 W
Power
Supply: Ac 110/120/220/240 V, 50/60 kHz
Dimensions
(W x H x D): 430 x 142 x 254 mm
(16-15/16" x 5-19/32" x 10")
Weight: 4,2kg (9,3 lbs)
Nessun commento:
Posta un commento