Shure UC2 User manual

E1998, Shure Brothers Inc. Printed in U.S.A.
25A1044 (RI)
Service Manual
UC2 Hand-Held
UHF Transmitter
Characteristics
General The Shure UC2 Hand-Held UHF Transmitter is a microprocessor-
controlled microphone transmitter, operating in the 774 to 862 MHz
frequency range. The UC2 hand-held transmitter is used in mid-level
installed sound, rental, and concert sound applications. Six frequency
range variations are available.
Controls and Connectors
1. Mic Cartridge Grille (87 shown)
2. Battery Fuel Gauge LEDs
3. Power ON/OFF Switch
4. Audio Gain Control
5. 9 V Battery
6. Battery Cup
7. Group Selection Rotary Switch
8. Channel Selection Rotary Switch
Figure 1. UC2 Controls and Connectors
1
2
3
48
75
6
Service Note: Shure recommends that all service procedures be
performed by a Factory-Authorized Service Center or that the
product be returned directly to Shure Brothers Inc.

Shure UC2 Hand-Held UHF Transmitter
2
Characteristics
25A1044 (RI)
Circuit Description
CONTROL
PLL CONTROL MCU EEPROM
(MEM)
PWR. OFF DETECT
+5V
REG.
GROUP CHANNEL
SYNTH.
RF POWER RF MUTE RF MUTE
VCO
FROM
BATT.
UNREG. PWR.
+5v
AUDIO IN
PWR.
HOLD
CIRCUIT
ON / OFF
SWITCH
FET
BYPASS
TONE KEY
CIRCUIT
Σ
TONE CONTROL
TONE KEY
CALL ID
BATTERY
MGMT.
& FUEL
GAUGE
AUDIO
OUT
LIMITER
CONTROL OUTPUT
LIMITER
CONTROL INPUT
MIC
Figure 2. UC2 Hand-Held Transmitter Circuit Block Diagram
32.768 kHz
4 MHz
4 MHz
MB15A02
MC68HC705
Audio Section
FCC-Approved
Audio enters L200, an inductor used as an rf choke. The signal is
ac coupled through capacitor C200 into a user adjustable gain stage.
Resistors R202 and R203 set up a half-supply bias, and R204 sets the
input impedance for the stage.
The back-to-back diodes, D201, are used to keep the op-amp from
snapping to the rail and reverse phasing when the maximum input volt-
age range is exceeded.
The 30 dB adjustable gain stage is built around U200A. The user
externally controls the gain of this stage. C206, C207, and C208 protect

Shure UC2 Hand-Held UHF Transmitter
Characteristics 325A1044 (RI)
the amplifier and bias circuits from rf interference. Due to its topology,
this stage is unique because it is non-inverting and allows for a gain less
than unity.
Audio then enters a buffer to the pre-emphasis network and the
compression stage. R213, R214, and C211 set up two corners for the
pre-emphasis network. The pre-emphasis boosts the high frequencies
before transmission.
This network feeds an NE575 compander, U202, that utilizes an
external amplifier, U201B. The compander performs a 2:1 logarithmic
compression of the audio signal. The pre-emphasis network also plays
a role in setting the hinge point (0 dB gain) of the compander.
From the compressor, the processed audio enters a low-pass filter,
U201D, and then a summing amplifier, U201C. The tone key (and for
J frequencies, the call ID signal) is added here to the processed audio
signal.
Transistors Q208 and Q209, with crystal Y200, form the tone key
oscillator circuit to provide a stable, continuous 32.768 kHz sine wave.
Transistor Q210 buffers the tone key signal before it is added to the
audio signal.
The tone key signal is used in the receiver to provide audio output
only when the tone key signal is present with the transmitted signal. If
the tone key or the transmitter is turned off, the receiver will be muted.
The tone key squelch eliminates receiver noise associated with
loss of a carrier. Q211 acts as a switch for toggling the tone key MUTE/
UNMUTE; it is controlled via the microprocessor.
The tone key signal, along with the processed audio signal, is then
fed to a summing amplifier, U201C. R244, at the output of the summing
amplifier, helps prevent spurious oscillations from the op-amp. After
passing the ac coupling capacitor, C243, the signal is fed to the rf module
via the rf choke, L207.
The battery meter circuit is comprised of U205; LEDs D203, D204,
D205; and various resistors. The meter works by comparing a divided
down version of the battery voltage (R250, R251) to two thresholds
(set by R252, R253, and R254), and lighting the appropriate LED.
A 9 Vdc battery provides power to the audio printed circuit board
(pcb), via switch S200. FET Q203 provides electrical reverse battery
protection by connecting the negative battery terminal to the pcb ground
only when the battery is connected with the correct polarity.
The 9 Vdc then enters U203, a low dropout 5 V regulator, which
gives a clean, regulated 5 V supply to run the audio circuitry. The
regulator has appropriate bypass capacitors on its input and output.
Q201, Q202, Q212, Q213, and their respective resistors, provide
power management and timing.

Shure UC2 Hand-Held UHF Transmitter
4
Characteristics
25A1044 (RI)
ETSI-Approved
This transmitter uses the same pcb as the domestic system, but it
requires a different topology and different parts.
A limiter is inserted between the pre-emphasis and the compressor
to limit the occupied bandwidth.
The buffer after the gain stage, U201A, is now an inverter with
pre-emphasis and 20 dB of attenuation. Previously bypassed, the
expander side of the NE575 (U202) is now activated and used as a
limiter. A sample of the audio is taken from the limiter output, U202,
pin 6, and sent to a control circuit that detects signals above a limiting
threshold. The comparator then sends a control signal to U202, pin 5,
which clamps the signal.
Rf Section
Processed audio enters R320, an internal potentiometer that is
adjusted for 45 kHz deviation (40 kHz for England), 100% modulation,
with a 6.8 dBu 1 kHz tone at the output of the compressor. For J fre-
quencies, R320 is adjusted for 5 kHz deviation with 1 kHz tone injected
into the mic input, to give –23.47 dBu at U201, pin 7 (TPA4).
The audio is then fed to the tuning voltage pin of the voltage con-
trolled oscillator (VCO), which modulates the carrier directly. A phase
locked-loop (PLL) frequency-synthesized system eliminates the need for
multiplier stages and results in a much higher degree of spectral purity.
The VCO is shielded to prevent external rf fields from affecting its
operation. Regulated 5 Vdc power from the low drop-out regulator,
U311, is provided to ensure frequency stability with changes in battery
voltage.
The VCO is capable of tuning from 782 to 806 MHz (FCC-approved),
with a 1 to 4 V tuning voltage range. At the output of the VCO, the rf
signal splits into two paths. Frequency variations by country are given
in a table in the Service Procedures section.
The output of the VCO is coupled by C323 to the frequency control
pin of the synthesizer, U304. The synthesizer’s internal circuitry divides
the rf signal down, as necessary. The synthesizer contains a quartz-con-
trolled reference oscillator circuit operating from a 4.0 MHz crystal, Y302,
that is adjusted by trimmer C314.
The transmitter output frequency is user-selectable in groups of
compatible channels from 782 to 806 MHz for domestic groups. Fre-
quency selection is made via microprocessor U303, which interfaces with
the user by means of the Group/Channel switches, S301 and S302.
The output of the synthesizer is a series of pulses integrated by a
passive loop filter (R316, C319, R317, C353, R318, C320) to produce a
control voltage signal. The control voltage signal is then connected to
the VCO through buffer amplifier U306B, which is used to isolate the PLL
filter from the audio modulation signals.

Shure UC2 Hand-Held UHF Transmitter
Characteristics 525A1044 (RI)
The VCO output is also coupled to the pre-driver and rf power
amplifier through a resistive network (R322, R324, R325) and a
coupling capacitor, C329.
The pre-driver stage, Q302, provides approximately 6 to 8 dB of
gain, which makes up for the pad. R326 and R327 provide base bias
for the transistor, while R328 sets its operating current.
L303 is an rf choke used to provide power to the stage, while L304,
C332, C333, C357, and C2 provide filtering/matching for the stage. The
collector of Q302 feeds into the power amplifier stage via coupling
capacitor C338 and a pi-matching network made up of C339, L305,
and C340.
The rf power amplifier, Q304, is a dual emitter BJT. This high-gain,
high-frequency low-noise device can provide +18 dBm out at its 1 dB
compression point. It is biased via base resistors R331 and R332. Its
operating current is controlled via emitter resistor R333.
L306 acts as a choke, and C349, C350, C355, and C356 provide a
good emitter bypass to ground. The amplifier output is matched to low-
pass filter U1, via L307. The low-pass filter output couples to the printed
circuit board (pcb) via C347 and L308.
The transmitter can deliver +17 dBm (50 mW) maximum to the
antenna for domestic frequencies; JA and JB frequency transmitters can
deliver +10 dBm maximum to the antenna. During transmitter power-up
and frequency selection, the rf power is muted by bringing the gates of
Q303/Q305 low. This provides approximately 45 dB rf attenuation until
the PLL has locked.
The transmitter rf is then unmuted by bringing the gates Q303/Q305
high. During transmitter power off conditions, voltage is first removed
from the VCO by bringing the base of Q301 high. Thus, the carrier signal
of the transmitter is not allowed to drift off frequency during power on/off
conditions.
Digital Section
The digital section contains several circuitry blocks.
Microcontroller Section
The microcontroller section consists of the U303 microcontroller.
The rotary switches indicate the UHF frequency group and channel. A
4.000 MHz oscillator provides the operating frequency to the microcon-
troller. The oscillator circuit includes C300, C301, and Y301. U5, R306,
and C305 form the reset circuit. U5 is the reset IC that resets the U303
microcontroller if the 5 Vdc normal operating voltage falls below 4.3 Vdc.
C302 and C303 form the power supply bypass filter circuit.

Shure UC2 Hand-Held UHF Transmitter
6
Characteristics
25A1044 (RI)
Memory Section
The memory section consists of U302, a non-volatile, Electrically
Erasable/Programmable Read Only Memory (EEPROM) that stores the
mapping of the compatible groups and channels. The microcontroller
serially communicates with this part via data and clock lines to read the
frequency corresponding to the Group and Channel position.
The ability to write to the memory occurs during factory programming
only. During normal usage, this memory is used as a look-up table only.
R335 and R305 resistors allow the clock and data lines to be driven
independently of the microcontroller port pin states during in-circuit pro-
gramming of the EEPROM.
Battery Management Section
The U303 microcontroller provides low battery shutdown. The shut-
down threshold is 1.88 Vdc ±10%. A voltage lower than the shutdown
threshold on U303, pin 17, shuts down the transmitter. Resistors R308
and R309 divide down the battery voltage for U303; a battery voltage
less than 5.65 Vdc must shut down the transmitter.
This auto shutdown disables the audio tone key mix, mutes the rf
output, and powers down the rf output amplifier section. The current
draw from a 9 Vdc battery in this state is 14 ±2.0 mA, and the battery
fuel gauge is not functional. Turning off the power switch completely
shuts off the transmitter.
The audio circuit description section provides information for the
battery fuel gauge circuit description.
Rotary Switches for Frequency Selection
A 10-position Group switch (S302) and a 16-position Channel switch
(S301) select the transmitter frequency. Both rotary switches share the
same U303 microcontroller port pins (3 through 6) for a multiplexed
switch read operation. The individual switches are selected by U303,
pins 7 and 8. Resistors R4, R300, R302, and R303 are the pull-ups for
the switch position read. Diode packs D301 through D304 isolate the
switches during the multiplexed read operation.
The multiplexed scheme to read switches does not allow incorporat-
ing switch change detection based on interrupts. Also, the switches can-
not be constantly scanned to determine changes because the scanning
frequency being in audio range is difficult to filter out.
In a steady state, the switch selector common pins are inputs to the
U303, pins 7 and 8, while U303, pins 3 through 6, are outputs. In this
state, pins 4, 5, and 6 are held low while pin 3 is held high. This forces
logic high level on switch selector pins if the switches are set on odd
positions. For even position settings, the contact on pin 1 is open from
the switch common pin and the internal pull-down resistors force logic
low to U303, pins 7 and 8.

Shure UC2 Hand-Held UHF Transmitter
Characteristics 725A1044 (RI)
Any switch change is comprised of state toggle from odd to even,
and vice versa. Only this change is detected, and it is followed by a
multiplexed switch read, in which U303, pins 7 and 8, become selectively
grounded outputs to read the selected switch’s state on pins 3 through 6.
A multiplexed switch read is preceded by tone key and rf mutes.
This mutes the audio in the receiver to allow a quiet change to another
frequency.
For JA frequencies, the Group switch has 16 positions, and the
Channel switch has 10 positions.
Power Switch and Mute Interface
When a transmitter is turned off, the PWRDN signal goes to logic low
on U303, pin 19. This immediately disables the tone key, and the power
hold circuit automatically kicks in to bypass the power switch. This is
followed by 500 mS of delay, and then the rf is muted and turned off.
The power hold circuit is also disabled at this point, and the transmitter
shuts off.

Shure UC2 Hand-Held UHF Transmitter
8
Notes
25A1044 (RI)
Notes
This page intentionally left blank.

Shure UC2 Hand-Held UHF Transmitter
Functional Test 925A1044 (RI)
Functional Test
Verify operation and reported malfunction, referring to the product
User’s Guide for a description of the unit as well as information on its
operation, troubleshooting, and technical data.
Disassembly and Assembly
! CAUTION !
Observe precautions when handling this static-sensitive device.
Disassembly
1. Remove the microphone cartridge from the UC2.
2. Use a pair of needlenosed pliers to remove the circuit board
retaining ring from inside the handle.
3. Push the bezel tab-snap in the handle behind the contact pcb to
remove the bezel and switch actuator.
4. Slide the circuit board out by pushing on the battery connectors.
Right side view of microphone
Bezel
Handle Tab
Circuit board subassembly
Tab
Figure 3. Bezel Removal
Contact pcb
Switch actuator

Shure UC2 Hand-Held UHF Transmitter
10
Disassembly and Assembly
25A1044 (RI)
ÁÁÁ
ÁÁÁ
ÁÁÁÁ
ÁÁÁÁ
ÁÁÁÁ
ÁÁ
ÁÁÁ
ÁÁÁÁ
ÁÁÁÁ
ÁÁÁÁ
ÁÁÁ
ÁÁÁ
Á
Á
ÁÁÁ
ÁÁÁ
ÁÁÁ
ÁÁÁ
Microphone
cartridge
(SM58 shown)
Ball screen
Contact
board
Gain control
Audio circuit
board
Bezel
Switch
actuator
9 Vdc alkaline
battery
Rf circuit
board
Gain control
access
Battery cup
Handle
Figure 4. UC2 Hand-Held Transmitter, exploded view.
Retaining
ring
Reassembly To reassemble the unit, reverse the disassembly steps given above:
1. Slide the circuit board back into the handle.
2. Reinstall the retaining ring, switch actuator, bezel, and the
microphone cartridge.

Shure UC2 Hand-Held UHF Transmitter
Service Procedures 1125A1044 (RI)
Service Procedures
Measurement Reference
dBu is a measure of voltage , and dBm is a measure of power .
For example, the HP8903 should be labeled dBu instead of dBm
because it is a voltage measurement. These two terms are often used
interchangeably even though they have different meanings.
Audio levels in dBu are marked as dBm on the HP8903.
dB Conversion Chart
0 dBV =2.2 dBu
0 dBu =0 dBm, assuming the load = 600 Ω
Test Equipment Most test equipment needed is described in the Shure
Wireless
Service Equipment Manual . The following test equipment (or approved
equivalent) is also needed.
Table 1
Test Equipment
Equipment Type Model
Audio analyzer *Hewlett-Packard 8903B
Digital multimeter Fluke 87
Rf signal generator Hewlett-Packard 8656B
Frequency counter Hewlett-Packard 53181A
Spectrum analyzer (domestic) Hewlett-Packard 8590L
Spectrum analyzer (JA, JB) Hewlett-Packard 8591E
Shure UC4 receiver Shure UC4
Test head PT1840
Brass ring for use with test head PT1838–Y
BNC to “rocket launch” cable 95C8418–1
*Audio levels in dBu are marked as dBm on the HP8903B.
Test Equipment Set-Up
The alignment procedure is sequential and does not change,
unless specified.
1. Use RG58 or any low loss, 50 Ωcables for all rf connections.
Use a BNC to “rocket launch” cable for J frequencies.
2. Keep the test cables as short as possible.
3. Include the insertion loss of the cables and connectors for all rf
measurements.
4. Dc voltages may be present at rf test points. As a precaution,
use dc blocks to protect the test equipment

Shure UC2 Hand-Held UHF Transmitter
12
Service Procedures
25A1044 (RI)
Test Set-Up
U200
AUDIO SIDE 1
D201
C200
J205 Q220
TP18
TP10
TP4
TP6
+5V
+9V
U201U202
C216 R7
U205
Y200
S200
GND
1
U203
Q203
Q202
Q204 Q209
Q201
Q212
Q213 C222 C214
PAD
C27
C291
RED
GREEN
S301
S302 RF GND*
TPRF1 J2*
R40*
Q304
Y302 C314
R320
U302
U303
Y301
U501
C510
1
TP30
TP+9
L302
Q301
C308
U311
C309
RF SIDE 1
AUDIO SIDE 2
RF SIDE 2
J202
J201
J302
J301
C227
C251
C223
C221
C210
Q211 Q210
Q208
Q3 Q2
U2
L1
Q1
C243
L207
TP2 TP16
TP6
TP4
TP10
C213
TP18
+9V
+5V
J200
J300
D304
D303
D302
D301
U5
C303
C324
U306
C353 U304 C315
C336
Q305
Q303
L300
U1U1 C347
L308
TPRF1
TP30
TP+9
1
1
R39
P201
P200
P203
P204
L2
R25
*J2 and R40 are placed for JA, JB frequencies only. RF GND is accessed thru a hole in the pcb.
Figure 5. UC2 Major Test Component Locations
1. Use the PT1843 cable to connect the audio board to the rf board
through the 11-pin board interconnects (J200, J300, side 2).
2. Apply + 9 Vdc across the battery terminals (J201, J202, side 2).
3. Set the audio GAIN potentiometer (R207, side 1) to minimum,
full counter-clockwise (CCW).
4. See Table 2 for frequency settings.

Shure UC2 Hand-Held UHF Transmitter
Service Procedures 1325A1044 (RI)
Table 2 lists the group carrier frequencies, switch settings,
and tuning voltages for all the alignment tests that follow.
Table 2
Group Carrier Frequencies and Tuning Voltages
(in order by carrier frequency)
Group Group
Code
Group
Switch
(S101)
Channel
Switch
(S102)
Carrier
Frequency
(MHz)
VCO Tuning
Voltage
(TP130) Deviation (kHz)
UA A 4 0 805.500 3.7 45
MB B 1 3 805.500 2.2 15
JA C 0 2 805.500 3.7 5
JB D 4 2 807.500 3.8 5
KK E 5 5 857.125 2.9 15
MC – – – – – –

Shure UC2 Hand-Held UHF Transmitter
14
Service Procedures
25A1044 (RI)
Alignment Use this service procedure to correctly align the transmitter’s
operating (output) frequency. C510 tunes the voltage-controlled
oscillator (VCO) to the operating frequency selected, with a 1 – 4 Vdc
tuning range.
C314 adjusts the reference oscillator on the synthesizer, U304.
AUDIO ANALYZER
RETAINING
RING
TEST
HEAD
FREQUENCY COUNTER
J205
J205 S200
AUDIO SIDE 1
TPRF1 C347
RF SIDE 2
CH 2
CH 1
UC2 Transmitter Audio Analyzer Frequency Counter
Power (S200): ON (+9 Vdc) Measurement: AC level Operating freq: See Table 2
Operating freq: See Table 2 Filters: Connect CH 2: TPRF1 and GND
Gain: Minimum Low-Pass (30 kHz): ON For JA,JB frequencies:
Connect to J2
High-Pass (400 Hz): ON
C
onnec
t
t
o
J2
(pcb rf side 1)
Figure 6. UC2 Frequency Alignment Set-Up
1. Remove C347 and connect a 50 Ωcable between TPRF1 /
RF GND and a frequency counter.
For JA, JB frequencies, do not remove C347. Connect a
“rocket launch” cable between J2 and the frequency counter.
J2 is only placed on the JA, JB frequency assemblies.
2. Use a PT1840 test head and brass ring (PT1838-Y) to connect
the audio analyzer to the UC2 audio input (J205). Turn ON the
Low-Pass (30 kHz) and High-Pass (400 Hz) filters on the audio
analyzer.
For bench testing, the audio analyzer can be directly connected
to the contact board gold contacts with clip leads.
3. Toggle the power switch, S200, to turn on the UC2 transmitter.
4. Set the UC2 Group and Channel switches, S301 and S302,
according to the group designators on the board and the
settings given in Table 2.

Shure UC2 Hand-Held UHF Transmitter
Service Procedures 1525A1044 (RI)
Frequency
Use this service procedure to correctly align the transmitter’s
operating (output) frequency. C510 tunes the voltage-controlled
oscillator (VCO) to the operating frequency selected, with a 1 – 4 Vdc
tuning range.
C314 adjusts the reference oscillator on the synthesizer, U304.
FREQUENCY COUNTER
DC VOLTMETER
+
–
CH 2
CH 1
TP30
C510
U501
C314
J2*
RF
GND
S302
RED
S301
GREEN TPRF1
*R40 and J2 are placed for JA, JB frequencies only.
RF GND: FEED THRU
HOLE ON PCB
R40*
UC2 Transmitter Frequency Counter DC Voltmeter
Power: ON (+9 Vdc) Operating freq: See Table 2 Connect + : TP30
Operating freq: See Table 2 Connect CH 2: TPRF1 and GND Connect – : RF GND
Channel switch: See Table 2 For JA,JB frequencies:
Connect to J2
Group switch: See Table 2
C
onnec
t
t
o
J2
(pcb rf side 1)
Figure 7. UC2 Frequency Test Set-Up
1. Put a dc voltmeter across TP30 (tuning voltage line) and
RF GND.
2. Adjust the VCO trimmer, C510, until the voltmeter reading
matches the appropriate entry in Table 2, ±0.125 Vdc.
3. Adjust the variable capacitor, C314, until the frequency counter
measurement matches the appropriate frequency in Table 2,
±1 kHz.
4. Leave the test cable connected to the rf output.
5. Turn the transmitter OFF.
6. The dc voltmeter can be removed from TP30.

Shure UC2 Hand-Held UHF Transmitter
16
Service Procedures
25A1044 (RI)
Power Output Measurement
The output power measurement ensures that the output signal is
strong enough for sufficient range when the system is in use. The output
power measurement also verifies that the output power is not above the
specified maximum level, to ensure compliance with regulatory agencies
standards.
SPECTRUM ANALYZER
TP30
C510
U501
C314
J2*
RF
GND
S302
RED
S301
GREEN TPRF1
RF GND: FEED THRU
HOLE IN PCB
*R40 and J2 are placed for JA, JB frequencies only.
R40*
UC2 Transmitter Spectrum Analyzer
Power: ON Frequency: See Table 2
Operating freq: See Table 2 Span: 200 MHz
Reference voltage: 20 dBm
Peak search: ON
Signal track: ON
Marker: ON
Figure 8. UC2 Power Output Measurement Test Set-Up
1. Remove the BNC cable end from the frequency counter and
connect it to the 50 Ωinput of the spectrum analyzer.. Use the
equipment settings shown in Figure 8.
2. Measure the output power. The output power should be:
UA, MB, MC frequencies: 16 + 1 / – 2 dBm
KK frequencies: 14 + 1 / – 2 dBm
For J frequencies, with C347 in place,
adjust R40 to obtain 8.8 ±0.5 dBm.
3. Turn the UC2 power OFF.
4. Remove the BNC end of the cable from the spectrum analyzer,
but leave the bare end soldered to the printed circuit board (pcb).
5. For JA, JB frequencies, leave the “rocket launcher” cable
connected.

Shure UC2 Hand-Held UHF Transmitter
Service Procedures 1725A1044 (RI)
Deviation Reference Voltage, Using a UC4 or U4S Receiver
Deviation must be set to make sure the companding systems be-
tween the transmitter and receiver correctly track each other. The level
coming out of the transmitter’s audio compressor must match the level
going into the receiver’s audio expander. A fixed gain structure does not
ensure an exact match, primarily because of variations in voltage-
controlled oscillators (VCOs).
This test requires a UC4 or a U4S receiver and is designed to tune
the transmitter regardless of the accuracy of the receiver’s tuning. It is,
however, recommended that a properly-tuned receiver be used to per-
form the transmitter deviation adjustment.
TK ON TK OFF
S501
(TONE KEY SWITCH)
UC4 RECEIVER (BACK)
RF SIGNAL GENERATOR
AUDIO ANALYZER DC BLOCK
UC4 RECEIVER (FRONT)
AB
SQUELCH
NOTE: DC VOLTAGES ARE PRESENT
AT MOST RF TEST POINTS. USE A
DC BLOCK ON THE RF SIGNAL
GENERATOR TO PROTECT
TEST EQUIPMENT.
UC4 Receiver Audio Analyzer Rf Signal Generator
Output: Unbalanced Measurement: AC level INT: FM
Gain: Maximum Filters: INT: 1 kHz
Squelch: Mid Low-Pass (30 kHz): ON Output amplitude: –60 dBm
Tone Key (S501): OFF High-Pass (400 Hz): ON Frequency: See Table 2
Group switch: See Table 2 Modulation: See Table 2
Channel switch: See Table 2
Figure 9. Deviation Reference Voltage Test Set-Up,
Using a UC4 or U4S Receiver
1. Connect the rf signal generator to one of the receiver’s
antenna port B.
2. Turn the UC4 or U4S receiver ON.
3. Set the receiver frequency to match the transmitter frequency.
4. Set the rf signal generator frequency to match the transmitter
frequency.
5. Modulate the generator frequency with 1 kHz audio at a
–60 dBm output level. See Table 2 for deviation.
6. Set the tone key switch (S501 for the UC4, S201 for the U4S)
to the OFF position.
7. Connect the ac voltmeter to the unbalanced output of the
receiver.
8. Read the ac voltage.
Record this voltage. This is the deviation reference voltage .

Shure UC2 Hand-Held UHF Transmitter
18
Service Procedures
25A1044 (RI)
Deviation Adjustment Voltage: Using a UC4 or U4S Receiver
AUDIO ANALYZER
S501
(TONE KEY SWITCH)
TPA4 –
U201,
pin 7
AUDIO
SIDE 1
UC4 Receiver UC2 Transmitter Audio Analyzer
Output: Unbalanced Power: + 9 Vdc Measurement: AC level
Gain: Maximum Gain: Minimum Frequency Output: 1 kHz
Squelch: Mid Filters:
Tone Key (S501): ON Low-Pass (30 kHz): ON
High-Pass (400 Hz): ON
Figure 10. Deviation Adjustment Voltage Test Set-Up,
Using a UC4 or U4S Receiver, Steps 1 through 3
Reassemble the printed circuit boards for this test.
1. Disconnect the rf signal generator from the UC4 receiver and
return the UC4 tone key switch to the ON position.
2. Connect the audio analyzer output to the MIC input of the
transmitter, using the test head or clip leads to the gold spring
contacts.
3. Adjust the audio input level using the audio analyzer output to
measure the following at TPA4 (U201, pin 7) :
UA MB, MC JA, JB KK
–6.8 dBu ±0.2 dB
(354 mV ±1 mV) – 16.3 dBu (118 mV ±1 mV) – 23.47 dBu (52 mV ±1 mV) – 15.3 dBu (133 mV ±1 mV)
See Figure 11 for equipment set-up and equipment settings for
steps 4 through 6.

Shure UC2 Hand-Held UHF Transmitter
Service Procedures 1925A1044 (RI)
Deviation Adjustment Voltage: Using a UC4 or U4S Receiver
AUDIO ANALYZER
S501
(TONE KEY SWITCH)
RF
SIDE 1
R320
VCO
20 dB
UC4 Receiver UC2 Transmitter Audio Analyzer
Output: Unbalanced Power: + 9 Vdc Measurement: AC level
Gain: Maximum Gain: Minimum Frequency Output: 1 kHz
Squelch: Mid Filters:
Tone key (S501): ON Low-Pass (30 kHz): ON
High-Pass (400 Hz): ON
Figure 11. Deviation Reference Voltage Test Set-Up,
Steps 4 through 6, Using a UC4 or U4S Receiver
4. Connect the unbalanced output of the UC4 to the input of the
audio analyzer (ac voltmeter).
5. Connect the BNC end of the cable from the rf output of the UC2
to the antenna input of the UC4 through a 20 dB in line pad.
6. Turn the transmitter ON and adjust R320 until the ac voltmeter
on the receiver reads the same as the
deviation reference
voltage , measured above, ±0.1 dB; or ±0.2 dB for JA, JB
frequencies..

Shure UC2 Hand-Held UHF Transmitter
20
Service Procedures
25A1044 (RI)
Deviation Reference Voltage: Using a Modified SC4 IF Receiver
.
Deviation tests can also be performed using a modified SC4 IF
receiver. For instructions on modifying an SC4 receiver, consult the
Shure Service Equipment manual.
RF SIGNAL GENERATOR
AUDIO ANALYZER
DC BLOCK
NOTE: DC VOLTAGES ARE
PRESENT AT MOST RF TEST
POINTS. USE A DC BLOCK
ON THE RF SIGNAL GENERATOR
TO PROTECT TEST EQUIPMENT.
R
I
L
ZAD–1 MIXER
MODIFIED SC4 IF RECEIVER
ANTENNA INPUT B AUDIO OUT
TONE KEY SWITCH: OFF
SC4 IF Receiver Audio Analyzer Rf Signal Generator
Output: Unbalanced Measurement: AC level INT: FM
Gain: Maximum Filters: INT: 1 kHz
Squelch: Mid Low-Pass (30 kHz): ON Output amplitude: + 7 dBm
Tone Key switch: OFF High-Pass (400 Hz): ON Frequency: 10.7 MHz
Operating freq: See Table 2 Modulation: See Table 2
Figure 12. Deviation Reference Voltage Test Set-Up,
Using a Modified SC4 IF Receiver
1. See Figure 12 for equipment test set-up and equipment settings.
2. Connect the rf signal generator output to the input port (L) of a
Zad-1 mixer
3. Connect the output port I (intermediate frequency) of the Zad–1
mixer to antenna input B of the SC4 IF receiver.
4. Turn the SC4 IF receiver ON and set the tone key switch on the
front panel of the SC4 IF receiver to OFF.
5. Connect the audio voltmeter to the receiver’s unbalanced output.
6. Measure the output voltage.
Record this voltage. This is the deviation reference voltage .
Use the same Zad-1 mixer connections for the next adjustment test.