Motorola Vhf 136 174 Mhz Uhf 435 480 Mhz 6881096c38 Manual

							Chapter 7 VHF (136-174 MHz) Band Information 
7.1 Model Chart 
Business Portable Radio, VHF, 136-174 MHz
Model Description
AAH49KDF8AA1A_Business Portable, 136-174 MHz, 2-5W, 12.5/25 kHz, 16 Ch.
AAH49KDF8AA1A_ Business Portable, 136-174 MHz, 2-5W, 12.5/25 kHz, 4 Ch.
ItemDescription
X PMUD1925_ Business Portable, 136 -174 MHz, 2-5W, 12.5/25 kHz, 16 Ch.
XPMUD1922_Business Portable, 136 -174 MHz, 2-5W, 12.5/25 kHz, 4 Ch.
X DSAXRK210004 Front Housing Kit, Black CP125
XDSAXRK210001Front Housing Kit, Black BC120
X X DSAXRK210002 Front Housing Kit, Grey
XXPMDN4061_Chassis Hardware Kit (1-Piece Audio Jack R2)
X X DS1M001120 Chassis Hardware Kit (2-Piece Audio Jack)
XXDSAXRA110001Volume Knob Assembly
X X DSAXRK290001 LCD Kit
XXDSAXRA220001Speaker Assembly
X X DSAXRM2B0001 Screw M2.6
XXDSAXRM2A0001Battery Contact Gasket
X X DSAXRM250001 Main Gasket
XXDSAXRM120001Volume Knob Gasket
X X DSAXRM2C0001 Gasket (Screw 26)
XXPMDN4063ABack Chassis Kit (1-Piece Audio Jack)
X X DSM5190001 Back Chassis Kit (2-Piece Audio Jack)
XXDSAXRM140001PTT Button
X X PMNN4063_R Battery Std NiMH
XXPMAD4012_VHF Stubby 9cm Antenna, 136-155 MHz
X X PMAD4013_ VHF Stubby 9cm Antenna, 155-174 MHz
XXPMAD4014_VHF Helical 14cm Antenna, 136-155 MHz
X X PMAD4015_ VHF Helical 14cm Antenna, 155-174 MHz 
						

							March, 20066881096C38
7-2VHF (136-174 MHz) Band Information: Model Chart
XXPMAD4027_VHF Helical 15cm Antenna, 136-155 MHz
X X PMAD4028_ VHF Helical 15cm Antenna, 148-174 MHz
XXNAD6502_Standard VHF Heliflex Antenna, 150-162 MHz
X X PMTN4087_ Standard Rapid Rate Charger Kit, 120V
X3380384W23CP125 Nameplate
X DSAXRM160001 BC120 Nameplate
XXHLN9844_2 Spring Belt Clip
X 6881096C35 Business Portable Radio User Guide (English)
X6881098C60CP125 Radio User Guide (English/French)
X = indicates one of each is required.Business Portable Radio, VHF, 136-174 MHz
Model Description 
						

							Specifications7-3
March, 20066881096C38
7.2 Specifications
General
TransmitterReceiver
All specifications are subject to change without notice.
VHF
Frequency:136-174 MHz
Channel Capacity: 16, 4
Power Supply:7.5 Volts ±20%
Dimensions with Stan-
dard High
Capacity NiMH
Battery:115.5mm x 56mm x 35mm
Weight: with Standard 
High Capacity NiMH 
Battery:350 g
Average Battery Life @ 
(5-5-90 Duty Cycle)(Low Power)
>11 hrs(High Power)
>8 hrs
Sealing:Passes rain testing per IPX4 
(EN60529=1991)
Shock and
Vibration:Meets MIL STD 810C, D and 
E
Dust:Meets MIL STD 810C, D and 
E
Humidity: Weather resistant housing 
passes EIA RS-316B
VHF
RF Output
NiMH @ 7.5V:Low
2 WHigh
5 W
Channel Spacing 12.5/25 kHz
Freq. Stability
(-30°C to +60°C)0.00025%
Spurs/Harmonics: -26 dBm
Audio Response:
(from 6 dB/oct. Pre-
Emphasis, 300 to 
3000Hz)+1, -3 dB
Audio Distortion:
@ 1000 Hz, 60%
Rated Max. Dev.
						

							March, 20066881096C38
7-4VHF (136-174 MHz) Band Information: Theory of Operation
7.3 Theory of Operation
7.3.1 General Information
Your radio has two printed circuit boards: the Controller board, and the Radio Frequency (RF) and 
Audio Frequency board. The Controller board contains the CPU/Control section. The RF board 
contains the VCO/Synthesizer section, Transmitter section, Receiver section, Transmitter Audio 
circuitry, Receiver Audio circuitry, and Battery section.
7.3.2 Power Distribution
Figure 7-1.  
The above figure illustrates the DC distribution throughout the radio board. A battery supplies power 
directly to the electronic on/off control. Radio power supply is triggered by the Power Switch (On/
Off/Volume control) and +SW B is distributed as show in the figure. Regulator output 5V is supplied 
to the CPU. +SW B continues to support the Audio Power AMP, 5V Regulator, TX Regulator until the 
radio is turned off.
The radio can be turned off on two ways:
1.Power Switch turned-off
2. Low Battery
When a low battery level is detected by the CPU, it stores the radio personality data to EEPROM 
before turning off the radio.
7.3.3 Power up Sequence
1. Power supply is turned on by the On/Off/Volume Control (Power Switch).
2. Power from battery is supplied to the regulator through the switch.
3. Output (5V) from the regulator is directed to the CPU (Q101).
4.Q105 resets the CPU (Q101).
5. The CPU loads radio personality data from EEPROM after the reset.
6. This personality data is used to initialize the radio.
5V REG
Q204
RX SW
Q211
TX/RX SW
Q210, 211
TX REG
Q201,202
RF AMP
Q404Local AMP
Q416IF AMP
Q408IF AMP
Q506LPF
Q502HPF
Q505
Audio Power
AMP
Q702
RF PA
Q411Driver AMP
Q412
MIC AMP
Q602Sub Audio
LPF Q610
VCO Buffer
Q308PLL IC
Q323
RF Power
Control
Q419TX Driver
Q413,414
+ SW BSAVE SW
Q210RX +5V
TX +5V
TX/RX SW
Q309,310TX VCO
Q325
RX VCO
Q324
Battery
Diode
Q126
Reset
Q105CPU
Q101EEPROM
Q114DA
Converter
Q121
Ripple Filter
Q330
Power
Switch
SW201 
						

							6881096C38March, 2006
VHF (136-174 MHz) Band Information: Theory of Operation 7-5
7. The radio restores last power up state (i.e. state before the radio was turned-off).
8. Power is supplied to PLL circuitry.
9. Power is supplied to Rx and Rx VCO circuitry.
10. CPU sends data to PLL circuitry. If LOCK status is confirmed, radio continues the power-up 
sequence. Otherwise, PLL ERR is displayed.
11. If the Rx audio level is less than the pre-programmed squelch level, and other unmuting 
conditions are met, the radio will open squelch.
7.3.4 CPU / Control Section
When the radio is turned ON, the CPU (Q101) reads the radio status from the EEPROM Q114.   It 
also monitors the keypad, the PTT line and other inputs such as the squelch detect, etc. 
continuously. When there is a channel change, the CPU sends the correct frequency information to 
the synthesizer via pins 2, 87, and 100. The CPU is clocked by the 8.388608MHz oscillator, which is 
composed of X101, C101, C106, and R158.
7.3.5 VCO / Synthesizer Section
This section consists of the Temperature-Compensated Crystal Oscillator (TCXO), Voltage 
Controlled Oscillator (VCO), Synthesizer and the Loop Filter. These circuits are found on the RF 
board.
7.3.5.1  Temperature-Compensated Crystal Oscillator (TCXO)
The reference oscillator is a temperature compensated crystal-controlled, Pierce type circuit. It 
utilizes a logic gate within Q323 as a gain element. C335 is used to adjust the oscillator on frequency 
(14.4MHz) at room temperature (22°C). Temperature variations cause resistance changes in 
thermistor R330 and R567, which is on the base of Q320, thus varying the voltage applied to 
varactor Q322. This changes the impedance across crystal X301 in a manner complementary to the 
temperature drift characteristic of the crystal. In this way, the reference oscillator is held within the 
specified ±2.5 PPM from -30 to +60°C.
7.3.5.2  Voltage-Controlled Oscillators
Only one of the VCOs runs at a time, which is controlled by Q310 and Q101. The receive VCO 
consists of C344-C351, L302, L305, L306, L312-L314, Q311, and Q324. This VCO oscillates at 45.1 
MHz above the programmed receive frequency. The VCO’s oscillating frequency is tuned by the 
varactor Q311. The tuning voltage is supplied from the output of the Loop Filter. The output of the 
VCO is AC coupled (C352) to the synthesizer and the output buffer Q308 respectively. The output of 
the VCO buffer Q308 is AC coupled (C475 and R442-R444, C312, C313) to the synthesizer and the 
output buffer Q416 respectively.
When the PTT is pressed, Q101 pin 36 goes low (approx. 0V) disabling the receive VCO by the 
Q310 and biases on Q309 to enable the transmitter VCO. The transmitter VCO consists of C353, 
C355, C357, C358, L315, L317, L318, Q325, Q326, and 
Q329. This VCO oscillates on the 
programmed transmit frequency. The VCO’s oscillating frequency is tuned by the varactor Q326. The 
tuning voltage is supplied from the output of the Loop Filter. The transmit voltage controlled oscillator 
is directly frequency-modulated and operates on the carrier frequency. In the receive mode, the 
transmit VCO is disabled and the receive VCO is enabled, producing the receive local oscillator 
signal at a frequency 45.1 MHz above the incoming receive frequency. The synthesizer is tuned in 
5.00 kHz or 6.25 kHz steps. 
						

							March, 20066881096C38
7-6VHF (136-174 MHz) Band Information: Theory of Operation
7.3.5.3  Synthesizer
The frequency synthesizer is a large-scale monolithic synthesizer integrated circuit Q323. The 
synthesizer IC contains a dual modulus prescaler, programmable divide-by-N counter, prescale 
control (swallow) counter, reference oscillator, reference divider, phase detector, charge pump and 
lock detector. Also, included in Q323 are shift registers and control circuits for frequency controls and 
general device control.
RF output from the active VCO is AC coupled to the synthesizer Q323 prescaler input at Pin 8. The 
divide counter chain in Q323, consisting of the dual-modulus prescaler, swallow counter and 
programmable counter, divides the VCO signal down to a frequency very close to 5.00 kHz or 
6.25 kHz which is applied to the phase detector. The phase comparator compares the phase with the 
5.00 kHz or 6.25 kHz reference signal from the reference divider and drives the external charge 
pump (Q314, Q315 and Q301). The synthesizer unlock detector circuit prevents the operation of the 
transmitter and receiver, when the phase lock loop (PLL) is unlocked. The following discussion 
assumes the unit has been placed in the transmit mode. Q323 lock detector Pin 7 goes high when 
the PLL is locked. This high level is applied to Pin 25 of the CPU Q101. A software timing routing 
brings the RX/TX line low (Pin 36 of Q101). With the RX/TX line goes low, Q209 is cut off and Q208 
is biased on passing +5VTX-B to Q202; it biases on Q201 to pass switched TX-B to the transmitter 
amplifier string which enables transmission.
When the PLL is unlocked, the lock detector at Q323 Pin 7 will begin pulsing low. A RC circuit 
converts this low pulse to a low level for the CPU. The CPU then changes the RX/TX line to a high, 
thus signaling the other transistor switches to drive Q201 into cutoff, which disables transmission. 
Therefore, the transmitter remains disabled while the loop remains out of lock, and “PLL ERR” is 
displayed.
7.3.5.4  Loop Filter
The Loop Filter, a passive lead-lag filter consisting of R314-R317, R356, C323, C369, and C371, 
integrates the charge pump output to produce the DC turning voltage for the VCO. One parasitic 
pole, consisting of RF chokes L306/L318, prevent modulation of the VCOs by the 5.00 kHz or 
6.25 kHz reference energy remaining at the output of the loop filter. Direct FM is obtained for 
modulating frequencies outside the PLL bandwidth by applying the CTCSS/DCS signals and the pre-
emphasized, limited microphone audio to the VCO modulation circuit. The modulation circuit 
consists of R347 and Q329.
7.3.6 Transmitter Section
7.3.6.1  RF Power Amplifier
After the PTT is pressed, the +5VTX-B line switches to approximately 5V. Q309 is turned on, 
enabling transmit VCO. The VCO buffer, pre-driver, driver and power amplifier are biased on by 
Q201. Q201 is biased on by the +5VTX-B line switching to 5V. RF output from the transmit VCO 
(Q325) is applied to the VCO output buffer Q308. Output from Q308 feeds the buffer Q414. The 
output signal from Q414 feeds the pre-driver amplifier Q413, and feeds the driver amplifier Q412, 
whose output from the driver stage feeds the final RF power amplifier Q411 to produce the rated 
output power of 5 watts. The final output feeds to a low-pass filter (C446-C448, C451, C452, L418, 
and L419) and then to the transmit/receive switch Q410. RF power is then fed to the antenna via the 
output low-pass filter consisting of C440-C445, L415, and L416.
7.3.6.2  Antenna Switching
Switching of the antenna between the transmitter and the receiver is accomplished by the antenna 
transmit/receive switch consisting of diodes Q409 and Q410. In the transmit mode, switched TX B+ 
is applied through R419 and RF choke L417, hard forward biasing the two diodes on Q410, thus 
permitting the flow of RF power from the output of the low-pass filter. L414 and C445 isolate the 
receiver circuit from the transmitter power input. 
						

							6881096C38March, 2006
VHF (136-174 MHz) Band Information: Theory of Operation 7-7
7.3.7 Power Control
Output power is controlled by the CPU (Q101), the D/A converter (Q121), the dual Op-Amp (Q419), 
which is used as a differential amplifier and comparator. Current is sensed by the voltage drop 
across R445. When the radio is in high power mode, this voltage is compared to the D/A converter 
voltage at 5-watt. When the radio is in low power mode, this voltage is compared to the D/A 
converter voltage at 1-watt. The power output is then reduced or increased by varying the applied 
voltage to the gate of the power amplifier Q411 and Q412.
7.3.7.1  Transmitter Audio Circuits
The transmitter audio circuits consist of the audio processing circuits, the CTCSS circuits and the 
DCS circuits.
7.3.7.1.1  Audio Processing
Transmit speech audio is provided by either the internal electric microphone M101 or the external 
microphone. The audio is pre-emphasized by 6 dB per octave by C615 and R655, and then its signal 
is amplified. The microphone audio is directed to amplifier Q602B, Q602A, low-pass filter Q602C, 
and Q602D. Q602A has limiting function. The modulation adjustment is done by potentiometer 
RV601, and directed to a four-pole active low-pass filter. The resulting signal is then limited, and is 
directed to a low pass filter (-18 dB per octave roll-off above 3 KHz). The audio is then directed 
through the 25 KHz/12.5 KHz channel spacing SW Q601 to varactor diode Q329 in transmit VCO. By 
varying the voltage on the varactor diode Q329 at an audio rate, VCO output is frequency-
modulated.
7.3.7.1.2  CTCSS Tone Encoder / Digital Code Squelch (DCS) Encoder
CTCSS signals and DCS signals are synthesized by CPU Q101 and appear as pulse waveform on
I/O line Pin 7. This I/O line is directed to a digital-to-analog converter network (consisting of C136, 
C173, R150, R177 and R182), which produces a pseudo-sine wave at its output. The waveform is 
smoothed by low pass filters Q610B to produce an acceptable sine wave output. The CTCSS tone 
signal is adjusted to the proper level by RV602.
7.3.8 Receiver Section
7.3.8.1  Receiver Front End
In the receive mode, the RF signal enters thorough the antenna, then through the low-pass filter 
C439-C445, and L414-L416. The diodes Q409 and Q410 are biased off, so that the output of the 
low-pass filter is coupled (C437, C438, L413 and R418) to the first band-pass filter C401-C406, 
C408-C410, L401, L402, PCB_L1, Q401, R401, and to the Front End RF overload protection diode 
pair Q403. The signal from the band-pass filter is directed to the input of the RF amplifier Q404. The 
output of the RF amplifier is sent to three stages of band-pass filters, consisting of C415-C429, 
C486, L404-L406, Q405 and R410. The output from the band-pass filter is directed to the mixer 
Q407/L407.
7.3.8.2  Local Oscillator (LO)
The Receive VCO (C344-C351, L302, L305, L306, L312-L314, Q311, and Q324) provides the LO 
signal. The VCO runs at 45.1 MHz above the desired receive frequency and is applied to output 
Buffer Q308/Q416. The output of the buffer is sent through the low-pass filter C430, C431, L409
, and 
to the mixer Q407/L408. 
						

							March, 20066881096C38
7-8VHF (136-174 MHz) Band Information: Theory of Operation
7.3.8.3  Mixer
The mixer is a DBM type (L407, Q407, L408). The mixer LO frequency is 45.1 MHz above the 
desired receiver frequency. When the receiver frequency is present, the mixer output will be a 
45.1 MHz signal. The mixer output is peaked for 45.1 MHz at L410, C432 and R413, and the signal 
is filtered by crystal filter F402 and amplified by Q408 before being directed to IF IC Q506. The 
45.1 MHz IF signal and LO frequency of 44.645 MHz (X501) are mixed in Q506. The 455 kHz 
ceramic filter, F501 or F502, filters the second mixer’s output. The resulting signal is the second IF 
signal. The mixer’s output is then fed to the internal limiting amplifier, and consequently to the FM 
decoder.
7.3.8.4  FM Detector and Squelch
The FM detector output is used for squelch, decoding tones and audio output. The squelch amplifier 
is inside of Q506, and its output is fed to an internal rectifier and squelch detector. The output on 
Q506 Pin 14 signals the CPU Q101 with a low (~0V) to unmute the radio. The audio is unmuted by 
the CPU Q101 Pin 41 switching to a high (~5V), thus biasing on Q503. The audio is then routed to 
the audio amplifier Q702 via the volume control SW201.
7.3.8.5  Receiver Audio Circuit
The detector’s audio output is fed to the tone (CTCSS and DCS) low-pass filter Q505A. Then the 
output of the low-pass filter is routed to the second stage filter Q505B. The output of Q505B is 
passed to Q505C. The output of Q505C is directed to the squaring circuit Q505D, and finally to the 
CPU Q101 Pin 22 for decoding.
The detector output feeds the audio high-pass filter Q502. The output of the audio high-pass filter 
feeds the Volume Control SW201 (VOL). From the wiper arm on the Volume Control, the audio is 
routed to Pin 4, which is the input to the audio power amplifier Q702. The output of the audio power 
amplifier is routed through the earphone jack J701 to the internal speaker SP701.
7.3.9 Battery Section
The battery connects to the contact (CN201). The positive terminal of the battery connects to the 
ON/OFF Volume control switch (SW201), and the negative terminal connects to PWB ground. Low 
battery is detected by R127/R128 and voltage regulator Q204.
Battery voltage status is monitored by Pin 19 of the CPU Q101 through R127/R128. When the 
battery voltage goes below the threshold voltage, “LOW BATT is displayed on LCD LC101. When 
the Radio is on a channel with no tone programmed, the BATTERY SAVER Mode is enabled when 
programmed. In the BATTERY SAVER Mode, the CPU Q101 generates a square wave signal on Pin 
37. The signal’s duty cycle varies according to what the BATTERY SAVE TIMER is set. When the 
CPU U101 Pin 37 goes high (approximately 5 V), Q210 is biased off, and Q211 is cut off, thus turning 
the supply off to IF IC Q506. 
						

							6881096C38March, 2006
VHF (136-174 MHz) Band Information: Block Diagrams 7-9
7.4 Block Diagrams
7.4.1 Complete
Figure 7-2.  
SAVE 5VRX 5V
DAC
RX
Key
Pad
Power
Input
TX 5V
BATTERY
5VDAC RXDAC TX
35
DTMF IN
RC
NETWORK
9
RC
NETWORK
3
MIC
M101CN701 CN101
27
31
4
15
16
22
25 2522 15
163 4 319 35 27
DAC
TX+ SW B
Ripple 
Filter
Q3305VSPK SP701
(1/2) DTMF
IN Detect
Detect 13 13
ANT
Hamonics Filter
C440-445
L415,L416
ANT
Switch
Q409,410
Matching
Network
C446-448,
451,452
L418,419
2-Pole
Band Pass
Filter
Q401
RF
AMP
Q404
2-Pole
Band Pass
Filter
Q405
Mixer
Q407
Coupler
R445
Local
Buffer
Q416
2-Pole
Crystal
Filter
F402
Buffer
AMP
Q414
Pre Driver
Q413
Power
Control
Q419
Power
SW
SW201
5V
REG
Q204SAVE
SW
Q210
TX
REG/SW
Q201
Q202
Over
Voltage
Protect
Q707-710
TX/RX
SW
Q208
Q209
VCO
Buffer
Q308
RX
VCO
Q311
Q324TX
VCO
Q325
Q326
TX/RX
SW
Q309
Q310
Audio
Modulator
Q329
Loop
Filter
Q314-316
Pin 15
   16CN701
Pin37
   38
   39 Pin 11
   10
    9 Pin 1
   2
TCXO
14.4MHz
X301Q334Sub Audio
Modulator
Q322
6 Pole
Ceramic
Filter
F501
IF
AMP
Q408
De-emphasis
Q502ASub Audio
LPF
Q505
HPF
Q502Audio
Power
AMP
Q702EXT Audio
Jack
J701
6 Pole
Ceramic
Filter
F502
PLL
Q323
EEPROM
Q114
CPU
Q101
PTT
S102
Mon
S101
LCD
LC101
Shift
Q102
X,tal
8.38MHz
X101Restart
Q133-Q138
Reset
Q105DA
Converter
Q121
CPU
Pin87
DIODE
Q126
CPU
Pin21CPU Pin22
CPU Pin36
LPF
(DTMF)
Q610A
Limitter
AMP
Q602A
MIC
AMP
Q602BVOX
AMP
Q610DATT
Q608
Q609
LPF
(Sub Audio)
Q610A
N/W
SW
Q601LPF
Q602C,DDeviation
Adj
RV601
EXT MIC
Jack
J701(1/2)
DC
AMP
Q125
IF IC  Q506
(2nd Mix,2nd Local,IF AMP,DISC,Noise AMP)
2nd Local
44.654MHz
X501
RX
SW
Q211
DC/DC
Converter
Q333
Volume
SW201
(VR)
Final
AMP
Q411
PA
Q412 
						

							March, 20066881096C38
7-10VHF (136-174 MHz) Band Information: Block Diagrams
7.4.2 Controller
Figure 7-3.  
7.4.3 VCO
Figure 7-4.  
Key
Pad
35
RC
NETWORK
9
RC
NETWORK3
MIC
M10127
31
4
15
16
22
25 13
EEPROM
Q114
CPU
Q101
PTT
S102Mon
S101LCD
LC101Shift
Q102Xtal
8.38MHz
X101
Restart
Q133-Q138 
Reset
Q105
DA
Converter
Q121
CPU
Pin87
DIODE
Q126
CPU
Pin21CPU Pin22
CPU Pin36
DC
AMP
Q125
CN101
RX Local
Buffer
TX
BufferDATA
Audio Sub Audio
TX/RX
SW CONTL
Ripple 
Filter
Q330
5V
VCO
Buffer
Q308
RX
VCO
Q311
Q324
TX/RX
SW
Q309
Q310
Audio
Modulator
Q329Sub Audio
Modulator
Q322
TCXO
14.4MHz
X301
Q334
Loop
Filter
Q314
Q315
Q316
PLL
Q323CN701
Pin37
   38
   39 Pin11
   10
    9 Pin15
   16
Pin 1
    2
TX
VCO
Q325
Q326
Power
RegulatorDC/DC
Converter
Q333