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UD-300
CIRCUIT DESCRIPTION
Pin description
Function
Remark
FM IF input
Input impedance:330 Q
FM IF bias
_
FM AFC output
When FM AFC is detuned,the ST LED goes off and the forced
monaural mode is set
AM demodulation output
:
MPX section,AM demodulation input.
MPX AM DET input
;
Input impedance:27kQ
FM descrimination output
FM demodulation output
Output impedance:5kQ
.
MPX selection.
FM demodulation input.
MPX FM DET input
;
Input impedance
MPX Pilot synchronism
MPX VCO stops by shorting the voltage at pin 10 to the VCC line at pin 3. A 3.3
detection filter
kQ
current limiting resistor is required.
MPX PLL loop filter
=
MPX separation control
=
MPX VCO
Ceramic oscillator
MPX L-ch output
_
Vai (2 1.5V ) : FM
Vio(< 1.5V) : AM
Vui (2 1.5V ) : IF CNT ON
Peeunt eeipot
Vio(< 1.5V ) : IF CNT OFF
SW combined use
VHi (2 1.5V):LED forced off
(Forced monaural mode)
Vio(< 1.5V):Normal
Input impedance:2kQ
AM AGC output
FM S meter output
AM MIXER output
=
AM RF input
=
Vreg=2.3V
AM OSC buffer output
FM SD ADJ combined use
37
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