TM-281A
10
Ref. No.
Use / Function
Operation / Condition / Compatibility
Q4
Oscillator
RX VCO
Q5
T/R switch
On when RX
Q6
Oscillator
TX VCO
Q7
T/R switch
Q8
Ripple fi lter
Q9
Buffer amplifi er
Output of VCO
Q10
RF amplifi er
Output of VCO
Q303
Drive amplifi er
TX driver
Q501
Tripler
16.8MHz × 3
Q502
SQL amplifi er
Noise amplifi er
Q503
IF amplifi er
Q504
Mixer
1st mixer
Q505
RF amplifi er
LNA
Q506
PC/TV switch
On when TX
Q701
AGC/ MIC mute
Q702,703
Beat shift switch
Active while beat shift is ON
Q704,705
AF mute
Active while AFM is “H”
Q706
Buffer amplifi er
RX audio
Q707
Over voltage
detection
Active when PS voltage is more
than 18V
Q708
DC switch (8R)
Active while RX
Q709
DC switch (8T)
Active while TX
Q710
DC switch (8R)
Active while RX
Q711
DC switch (8T)
Active while TX
Q712
AF mute
Active while SPM is “H”
Q713,714
DC switch (SB)
Active when power is ON
Q715
AF mute
Active while AMPSW is “H”
Q901
Key backlight
switch
Q902
DC switch
Q903
LCD backlight
switch
Q904
Brightness
function switch
D1
Voltage dropped
D2
Ripple fi lter
D3
VCO frequency
control
RX
D4
VCO frequency
control
TX
Ref. No.
Use / Function
Operation / Condition / Compatibility
D5
VCO frequency
control
RX
D6
VCO frequency
control
TX
D7
VCO modulation
D8
Ripple fi lter
D9,10
RF switch
TX/RX
D301
Voltage protection
5.1V Zener diode
D305
Protection
PC/TV
D306,307
ANT switch
On when TX
D309
ANT switch
On when TX
D311
ANT switch
On when TX
D312
Temperature
compensation
D313,314
APC voltage
detect
D316
Protection
D501,502
IF switch
Wide/Narrow
D503
Detection
Noise squelch
D504
Protection
D505,506
RF BPF tuning
D508,509
RF BPF tuning
D702
Surge absorption
CM
D704
Surge absorption
MIC key
D705
Surge absorption
RXD
D706
Surge absorption
PTT
D708
MIC mute
D709
Detection
AGC
D710
Protection
D711
Limiter
D712
Over voltage
detection
On when PS voltage is more
than 18V
D714
Reverse connec-
tion protection
D901
Reverse connec-
tion protection
D902
Surge absorption
6.2V Zener diode
D903~905
LED
Key backlight
D906~911
LED
LCD backlight
COMPONENTS DESCRIPTION