Lectrosonics UM250c User Manual

UM2 50C

FREQUENCY-AGILE UHF

BELT-PACK TRANSMITTER

OPERATING INSTRUCTIONS

Rio Rancho, NM

www.lectrosonics.com

UM250C

2

INTRODUCTION

UHF Belt-Pack Transmitter

Thank you for selecting the Lectrosonics UM250C frequency agile, belt-pack transmitter. The UM250C combines over
80 years of engineering experience with the very latest components, in a design that addresses the most demanding
professional applications.

The design of the UM250C was the direct result of numerous conversations with users, staging and touring companies
and dealers across the US. The specific concerns and needs brought up in these conversations led directly to the
development of the operational features offered on the UM250C. Two hundred fifty six frequencies are user selectable
in 100kHz steps to alleviate interference problems in travelling venues, and the low frequency roll-off is user adjustable
to adapt to varying acoustic environments and preferences.

The UM250C is a rugged, machined aluminum package with a removable, spring loaded belt clip. The input section
provides a correct input tap for virtually any microphone or line level audio source. 5 Volts of bias voltage is available
to power electret mics with either positive or negative bias. Level indicating LEDs are provided on the control panel to
make input gain settings quick and accurate, without having to view the receiver. The battery compartment accepts
any 9 Volt lithium or alkaline battery and makes a positive connection via self-adjusting contacts. The antenna is a
detachable, locking 1/4 wavelength flexible bronze cable that connects to a 50 Ohm SMA port on the transmitter.

Only the UM250C transmitter is covered in this manual. Companion receivers are covered in separate manuals. The
UM250C will operate with any 200 Series Lectrosonics receiver in the same frequency group.

TABLE OF CONTENTS

GENERAL TECHNICAL DESCRIPTION ...................................................................................................... 4

GENERAL ...................................................................................................................................................................... 4

DUAL BAND COMPANDOR ......................................................................................................................................... 4

NO PRE-EMPHASIS/DE-EMPHASIS ........................................................................................................................... 4

PILOT TONE SQUELCH ............................................................................................................................................... 4

WIDE-BAND DEVIATION .............................................................................................................................................. 5

LONG BATTERY LIFE ................................................................................................................................................... 5

FREQUENCY AGILITY ................................................................................................................................................. 5

ANTENNA ...................................................................................................................................................................... 5

CONTROLS AND FUNCTIONS .................................................................................................................... 6

INPUT JACK .................................................................................................................................................................. 6

POWER ON/OFF SWITCH ........................................................................................................................................... 6

POWER ON LED ........................................................................................................................................................... 6

FREQUENCY SELECT SWITCHES ............................................................................................................................. 6

MODULATION LEDS .................................................................................................................................................... 6

AUDIO LEVEL ................................................................................................................................................................ 6

ANTENNA ...................................................................................................................................................................... 7

ADJUSTABLE LOW FREQUENCY ROLL-OFF .......................................................................................................... 7

BATTERY INSTALLATION ............................................................................................................................. 7

THE BELT CLIP ............................................................................................................................................................. 7

OPERATING INSTRUCTIONS ...................................................................................................................... 8

OPERATING NOTES ...................................................................................................................................... 8

ADJUSTING THE TRANSMITTER FREQUENCY ....................................................................................... 8

MICROPHONE CORD TERMINATION ......................................................................................................... 9

5-PIN INPUT JACK WIRING ...................................................................................................................... 1 0

RF BYPASSING ........................................................................................................................................................... 10

BODY GROUND .......................................................................................................................................................... 11

LINE LEVEL SIGNALS ................................................................................................................................................ 11

WIRING HOOKUPS FOR DIFFERENT SOURCES ................................................................................................. 11

TROUBLESHOOTING ................................................................................................................................. 12

SERVICE AND REPAIR.............................................................................................................................. 1 3

RETURNING UNITS FOR REPAIR ............................................................................................................ 1 3

SPECIFICATIONS AND FEATURES ......................................................................................................... 1 4

LIMITED ONE YEAR WARRANTY ............................................................................................................. 1 6

The UM250B transmitter is FCC type accepted under Part 74: 470-608MHz and 614-806MHz

Rio Rancho, NM – USA

3

UM250C

GENERAL TECHNICAL DESCRIPTION

GENERAL

The 200 series uses 75kHz wide deviation for an ex­tremely high signal to noise ratio. The transmitter circuits
are all regulated to allow full output power from the
beginning (9 Volts) to the end (7 Volts) of battery life. The
input amplifier uses a Motorola 33078 op amp for ultra low
noise operation. It is gain controlled with a wide range
input compressor which cleanly limits input signal peaks
over 30dB above full modulation.

DUAL BAND COMPANDOR

Traditionally, compandors have been a source of distor­tion in wireless microphone systems. The basic problem
with conventional systems is that the attack and decay
times are always a compromise. If the time constants
are fast, high frequency transients will not be distorted,
but this will cause low frequency distortion. If the time
constants are slower, low frequency audio distortion will
be low, but high frequency transients will then be dis­torted. The 200 system introduces an entirely new
approach to solving this basic problem, called “dual-band
companding.”

There are actually two separate compandors in the 200
system, one for high frequencies and one for low frequen­cies. A crossover network separates the frequency
bands at 1kHz with a 6dB per octave slope, followed by
separate high and low frequency compandors. The attack
and release times in the high frequency compandor are
fast enough to keep high frequency transient distortion at

a low level, and the low frequency compandor uses
slower time constants, reducing low frequency distortion
to well below that of a conventional compandor.

NO PRE-EMPHASIS/DE-EMPHASIS

The signal to noise ratio of the 200 system is high enough
to preclude the need for conventional pre-emphasis (HF
boost) in the transmitter and de-emphasis (HF roll off) in
the receiver. Pre-emphasis and de-emphasis in an FM
radio system usually provides about a 10dB improvement
in the signal to noise ratio of the system, but the high
frequency boost in the transmitter must be removed in a
purely complementary manner or else the frequency
response of the original audio signal will be altered.

Pre-emphasis can also cause distortion in the receiver.
As this signal is passed through the IF filters in the
receiver, distortion can be produced, most noticeable at
full modulation. De-emphasis cannot be applied until the
signal is converted into audio, so there is no way around
this problem short of eliminating pre-emphasis altogether.
Neither of these problems occur in the 200 system. The
dual-band compandor in the 200 Series system essen­tially provides a dynamic pre-emphasis/de-emphasis
function with extremely low distortion.

PILOT TONE SQUELCH

The 200 system utilizes an ultrasonic tone modulation of
the carrier to operate the receiver squelch. This “pilot
tone” consists of a 32kHz signal mixed with the audio

1
2
3
4
5

MIC

JACK

LIMIT

LED

SHUNT

LIMITER

FREQ

SWITCHES

+5V BIAS

SUPPLY

BUFFER

SET
LED

DIVIDER

PHASE LOCKED LOOP

LF
ROLL-OFF

INPUT
AMP

FILTER

AUDIO
LEVEL

PEAK AUDIO

INDICATOR &

LIMITER
DRIVER

PRESCALER

LOW PASS

FILTER

LP

COMPANDOR

Vref

BASS

TREBLE

COMPANDED

LP FILTER

HP FILTER

AUDIO

UM250C Block Diagram

PILOT
TONE

OSC

Vreg

+5VDC

Vreg

+3.6VDC

VOLTAGE

CONTROLLED

OSCILLATOR

PWR

TRANSMITTER

COMPANDED AUDIO

TO XMTR

DELAY

CIRCULAR

50

ISOLATOR

+9VDC

PWR

LED

4

UHF Belt-Pack Transmitter

signal following the microphone preamp, just after the
compandor, to control the audio output muting of the
receiver. The pilot tone is filtered out of the audio signal
immediately after the detector in the receiver so that it
does not influence the compandor or various gain stages.
The basic benefit of the pilot tone squelch system is that
the receiver will remain muted until it receives the pilot
tone from the matching transmitter, even if a strong RF
signal is present on the carrier frequency of the system.
This is extremely important in applications that include an
automatic microphone mixer.

WIDE-BAND DEVIATION

The ±75kHz deviation improves the capture ratio, signal
to noise ratio and AM rejection of a wireless system
dramatically, compared to the more commonly used
±15kHz deviation.

LONG BATTERY LIFE

High efficiency circuits throughout the design allow over 2
hours of operation using a single 9 Volt alkaline battery.
(A 9V lithium battery will provide over 7 hours of opera­tion.) The battery compartment is a unique mechanical
design which automatically adjusts to fit any brand of
battery. The battery contacts are spring loaded to prevent
“rattle” as the unit is handled.

FREQUENCY AGILITY

The transmitter section uses a synthesized, frequency
selectable main oscillator The frequency is extremely
stable over a wide temperature range and over time.

Two rotary switches, located on the side panel of the unit,
provide 256 frequencies in 100kHz steps over a 25.5MHz
range. This alleviates carrier interference problems in
mobile or travelling applications.

ANTENNA

At UHF frequencies, where wavelengths and antennas are
shorter than at VHF frequencies, a resonant length wire is
preferred over using the microphone cable as the antenna.
The antenna on the UM250B consists of a flexible 1/4
wavelength bronze cable, detachable via an SMA connec­tor. The impedance of this connector is 50 Ohms.

Rio Rancho, NM – USA

5

UM250C

CONTROLS AND FUNCTIONS

Input Jack

Power LED

Power ON/OFF

Switch

AUDIO LEVEL

Control

Modulation LEDs

ANTENNA Connector

Low Frequency Roll-Off

Adjustment (Under Cap)

Power ON/O

Frequency Select

Switches

Batter y Compartment

INPUT JACK

The input on the UM250C accommodates virtually every
lavalier, hand-held or shotgun microphone available. Line
level signals can also be accommodated. Use a
Switchcraft TA5F connector on the cord. See the sepa­rate sheet titled “Transmitter 5-Pin Input Jack Wiring”
regarding the correct connections for various micro­phones, and other sources.

POWER ON/OFF SWITCH

Turns the battery power on and off. Even when the switch
is turned off or on abruptly, the pilot tone muting system
prevents “thumps” or transients from occurring.

POWER ON LED

Glows when the battery is good and the Power ON/OFF
switch is set to ON. A weak or dim LED means that the
battery is weak. When the LED goes out, there is about
15 to 30 minutes of operation left with alkaline batteries
and about 2 hours left with lithium. If the LED fails to
glow when the Power ON/OFF switch is set to ON, the
battery should be replaced.

The Power LED continuously monitors battery voltage. It
is at full brightness with a new 9 VDC alkaline or lithium
battery. As the battery voltage drops during use, the LED
brightness will also decrease. After about 7 hours of
operation (with a lithium battery) the battery voltage will
be about 7 Volts and the LED will be nearly out.

FREQUENCY SELECT SWITCHES

These two rotary switches adjust the center frequency of
the carrier. The 1.6M is a coarse adjustment and the
100K is the fine adjustment. Each transmitter is factory
aligned at the center of its operating range. The default
position is in the center of the transmitter’s range.

Since the internal circuits are all tightly regulated and the
RF output stage has a separate discrete regulator, the
transmitter will continue to operate to a battery voltage of
7 VDC. As the voltage drops to 6 VDC, the transmitter
will still operate, but with degraded performance.

A weak battery will sometimes light the POWER LED immediately

after turn on, but will soon discharge to the point where the LED will

go out, just like a flashlight with “dead” batteries.

Note

The combination of an accurate battery condition indicator
and regulation of all internal circuits provides much longer
battery life, as well as consistent performance over the
life of the battery.

MODULATION LEDS

Indicates the audio modulation level set by the MIC
LEVEL control.

“-20” LED Flickers or glows when sufficient audio

is present.

“0” LED Lights up when the input level is high

enough to cause limiting. The input
limiter has a very high overload thresh­old (over 30 dB).

Generally speaking, some limiting is desirable in normal
operation to improve the signal to noise ratio of the
system. The limiting action is not audible and does not
create distortion. A highly trained ear would hear only the
compression of the peaks in the audio signal, which is
desirable with most tape recorders and many sound
reinforcement systems.

AUDIO LEVEL

Used to adjust the audio input level for the proper modula­tion.

6

UHF Belt-Pack Transmitter

Swing the
door open

Press outward on the
battery door in this
direction

ANTENNA

The flexible wire antenna supplied with the transmitter is
cut to 1/4 wavelength of the center of the frequency block
(the frequency range) of the transmitter. It is removable
via an SMA connector. The SMA connector is a 50 Ohm
RF port which can also be connected directly to test
equipment. Replacement antennas are available in pre­cut lengths for specific frequency blocks, or as a kit with
instructions to cut the antenna for any frequency block.

ADJUSTABLE LOW FREQUENCY ROLL­OFF

A 18dB per octave low frequency roll-off is provided in the
audio section, with the -3dB point adjustable from 35Hz to
150Hz. The actual roll-off frequency will vary somewhat
according to the low frequency response of the mic
capsule being used.

The low frequency roll-off control is used to prevent
undesirable subsonic (or very low frequency) audio, often
produced by air conditioning systems, automobile traffic
and other sources from causing the compandor to
mistrack. Excessive low frequency content in the audio
input can cause “pumping and breathing” of background
noise or modulation of the program audio in recording
applications. In sound reinforcement systems, excessive
low frequency content can cause excessive power
amplifier drain or even damage to loudspeaker systems.
By rotating the control clockwise, the hinge point of the

roll-off is increased to reduce the level of low frequencies.
In controlled situations, such as a motion picture produc­tion set indoors where environmental noise is minimal,
the control can be rotated counter-clockwise to permit low
frequency audio to be captured.

THE BELT CLIP

The belt clip may be removed for special applications by
removing one screw.

Caution

USE ONLY THE SCREW THAT IS SUPPLIED

The circuitry is tightly packed into this unit. A longer
screw will permanently damage the transmitter! Use only
Lectrosonics #28528 which is a Phillips head, 4-40 x 3/
16", FL100 screw.

Belt Clip Retaining Screw

(Under Clip)

BATTERY INSTALLATION

The transmitter is powered by a standard alkaline or
lithium 9 VDC battery. It is important that you use ONLY
a LITHIUM battery for longest life. Standard zinc-carbon
batteries marked “heavy-duty” or “long-lasting” are not
adequate. Ni-cad rechargeable batteries will only provide
a few minutes of operation, or less, and will run down
quite abruptly. Alkaline batteries provide 2 hours of
operation. Lithium batteries will provide up to 7 hours of
operation. Care should be taken not to leave a fully
discharged lithium battery in the transmitter, as swelling
of the battery can make it difficult to remove from the
compartment. The battery status circuitry is designed for
the voltage drop over the life of lithium batteries.

To open the battery compartment, press outward on the
cover door in the direction of the arrow as shown in the
drawing. Only firm, sliding pressure is needed to open
and close the battery door. Swing the door open and take
note of the polarity marked inside showing the location of
the positive (+) and negative (-) terminals. You can see
the large and small contact holes inside the battery
compartment with the door open.

Insert the battery correctly and close the cover by
pressing the door closed and across, reversing
the opening procedure illustrated above. If the
battery is inserted incorrectly, the door will
not close. Do
not force the
door
closed.

Batter y Compartment

Rio Rancho, NM – USA

7

UM250C

OPERATING INSTRUCTIONS

1) Install a fresh battery according to the

instructions above.

2) Insert the microphone plug into the input jack,
aligning the pins; be sure that the connector
locks in.

3) Attach the antenna to the SMA connector on
the top of the transmitter.

4) Mute the sound system.

5) Turn the transmitter power switch to the “ON”

position.

6) Position the microphone in the location you will
use in actual operation.

7) While speaking or singing at the same voice
level that will actually be used, observe the
MODULATION LEDs. Adjust the AUDIO
LEVEL control knob until the LEDs begin to
light. Start at a low setting where neither LED

OPERATING NOTES

The AUDIO LEVEL control knob should not be used to
control the volume of your sound system or recorder
levels. This gain adjustment matches the transmitter gain
with the user’s voice level and microphone positioning.

If the audio level is too high — both LEDs will light
frequently or stay lit. This condition may reduce the
dynamic range of the audio signal.

If the audio level is too low — neither LED will light, or the

-20 LED will light dimly. This condition may cause hiss
and noise in the audio, or pumping and breating in the
background noise.

The first LED turns on 12dB below full deviation. The “0”
LED turns on at full deviation and indicates that the input

lights as you speak. Gradually, turn the gain
up until one LED lights, then the other.

The -20 LED lights when the audio level is
about 12dB below full modulation. The “0” LED
lights when the limiter begins to operate. There
is 30dB of limiting range without overload
above the “0” LED, so it is desirable that it
lights up occasionally during use.

8) Once the gain has been adjusted, the audio
system audio can be turned on to make level
adjustments. Set the Power switch to the ON
position and adjust the receiver and/or sound
system level as required. Please note, there
will be a delay between the moment the switch
is thrown and the time when audio will actually
appear at the receiver output. This intentional
delay eliminates turn on thumps, and is
controlled by the pilot tone squelch control.

shunt compressor is operating. The input limiter will
handle peaks over 30dB above full modulation, regardless
of the gain control setting. The limiter uses a true abso­lute value circuit to detect both positive and negative
peaks. The attack time is 5 milliseconds and the release
time is 200 milliseconds. Occasional limiting is desirable,
indicating that the gain is correctly set and the transmitter
is fully modulated for optimum signal to noise ratio.

Different voices will usually require different settings of
the AUDIO LEVEL control, so check this adjustment as
each new person uses the system. If several different
people will be using the transmitter and there is not time
to make the adjustment for each individual, adjust it for
the loudest voice.

ADJUSTING THE TRANSMITTER FREQUENCY

If you are experiencing interference from another signal
on your frequency, you may want to change the operating
frequency of your system. The left switch changes the
operating frequency by 1.6 MHz per step and the right
switch changes it 100 kHz per step. If you are experienc­ing interference, change the operating frequency in 100
kHz steps to find a clear channel. If it is not possible to
find a clear channel using the 100 kHz switch, return it to
its original position and change the 1.6 MHz switch by
one click then try the 100 kHz switch again.

To gain access to these switches, slide the access door
sideways with a fingernail.

With the UDR200A receiver, these switches also appear on the front

panel of the receiver. Normally, you should set the transmitter

switches to match the receiver switch settings.

8

Note

With the UDR200B receiver, the front panel LED character
display will indicate the correct transmitter switch set­tings.

0

1

F

E

D

C

B

A

2

3

4

5

6

9

7

8

1.6 MHz 100 kHz

0

1

F

E

D

C

B

A

2

3

4

5

6

9

7

8

MICROPHONE CORD TERMINATION

1

2 3

4

5

VIEW FROM SOLDER

SIDE OF PINS

0.3"

0.15"

Heatshrink
Tubing

TA5F Connector Assembly

Mic Cord Stripping Instructions

Caution!

Do not allow the shield wire to touch any
metal part of the connector shell.

The shield wire is the antenna on VHF
models and poor operating range will result.

Shield Wire

Crimp

Tabs

Rubber

Insulation

Crimp

Tabs

Rubber

Insulation

UHF Belt-Pack Transmitter

This termination is required on VHF transmitters and will still work fine on UHF transmitters.

Rio Rancho, NM – USA

Note

9

UM250C

5-PIN INPUT JACK WIRING

The wiring diagrams shown on the next page represent the basic wiring necessary for the most common types of
microphones and other audio inputs. Some microphones may require extra jumpers or a slight variation on the dia­grams shown.

When wiring the connector, do not use the connector body for any electrical connections.

A common mistake is to use the connector body as an audio ground. The connector body is

already used as an RF ground on VHF models and no other use is permitted.

It’s virtually impossible to keep completely up to date on changes that other manufacturers make to their products. It
is possible that you may encounter a microphone that differs from these instructions. If this occurs please call our toll­free number listed on page 13 of this instruction manual. Our service department can answer your questions regarding
microphone compatibility.

When used on a wireless transmitter, the microphone element is in the proximity of the RF coming from the transmitter.
The nature of electret microphones makes them sensitive to RF, which can cause problems with the microphone/
transmitter compatibility. If the electret microphone is not designed properly for use with wireless transmitters, it may
be necessary to install a chip capacitor in the mic capsule or connector to block the RF from entering the electret
capsule. This modification is shown on the next page.

Caution

LECTROSONICS

4

3

5

2

1

1

2

3

4

5

NEG GND (OR BIAS)

POS BIAS (OR GND)

MIC

SOURCE LOAD

LINE IN

330PF

1uH

330PF

100

1K

10K

5V Mic Bias
5mA max

+

To Mic Amp

Transmitter

Input Jack

VHF transmitters use the shield of the microphone cord as the antenna. The UM250C uses a 1/4 wave flexible wire to
radiate the RF signal. There is really not much difference between these two approaches, with respect to the effect of

UHF Transmitter Equivalent Input Circuit

the RF on the microphone capsule. Even in transmitters that utilize a “dangling wire,” the microphone is still part of
the “ground plane” and is therefore still in the antenna circuit.

PIN 1 Shield (ground) for positive biased electret lavalier microphones. Bias voltage source for

negative biased electret lavalier microphones. Shield (ground) for dynamic microphones and
line level inputs.

PIN 2 Shield (ground) for negative biased electret lavalier microphones. Bias voltage source for

positive biased electret lavalier microphones.

PIN 3 Low impedance microphone level input for dynamic microphones. Also accepts hand-held

electret microphones provided the microphone has its own built-in battery.

PIN 4 1K Ohm source load for non-Lectrosonics electret microphones. Use in conjunction with other

pins to provide attenuation of high level input signals.

PIN 5 High impedance, line level input for tape decks, mixer outputs, musical instruments, etc.

RF BYPASSING

Some mics require RF protection to keep the radio signal from affecting the capsule, even though the transmitter input
circuitry is already RF bypassed (see schematic diagram).

If the mic is wired as directed, and you are having difficulty with squealing, high noise, or poor frequency response; RF
is likely to be the cause.

10

UHF Belt-Pack Transmitter

R

3

The best RF protection is accomplished by installing RF
bypass capacitors at the mic capsule. If this is not pos­sible, or if you are still having problems, capacitors can be
installed on the mic wires inside the TA5F connector hous­ing.

Install the capacitors as follows: Use 330 pF capacitors.
Capacitors are available from Lectrosonics. Please specify
the part number for the desired lead style.

Leaded capacitors: P/N 15117
Leadless capacitors: P/N SCC330P

2 WIRE MIC 3 WIRE MIC

Preferred locations for bypass capacitors

SHIELD

AUDIO

CAPSULE

TA5F

CONNECTOR

Alternate locations for bypass capacitors

CAPSULE

SHIELD

AUDIO

BIAS

TA5F

CONNECTO

All Lectrosonics lavalier mics are already bypassed and do not need any additional capacitors installed for proper
operation.

BODY GROUND

When wiring the connector, do not use the connector body for any electrical connections. A common mistake is to use the connector body

as an audio ground. The connector body is already used as an RF ground on VHF models and no other use is permitted.

Caution

LINE LEVEL SIGNALS

The normal hookup for line level signals is: Signal Hot to pin 5, Signal Gnd to pin 1, pin 4 jumped to pin 1, and pin 3
jumped to pin 1. This gives a 40dB attenuator that allows signal levels much higher than 3V to be applied without
distortion.

If more headroom is needed, insert a 100k resistor in series with pin 5. Put this resistor inside the TA5F connector to
minimize noise pickup.

If lower than normal line levels (less than 1V) are expected, use this hookup: Signal Hot to pin 5, Signal Gnd to pin 1,
and pin 4 jumpered to pin 1. This provides a 20dB attenuator allowing signals as high as 3V to be applied without
distortion.

WIRING HOOKUPS FOR DIFFERENT SOURCES

PIN

PIN

PIN

1

2

3

4

5

1

2

3

4

5

1

2

4

3

4

5

4

3

TA5F

PLUG

4

3

PLUG

3

TA5F

PLUG

5

5

TA5F

5

1

2

1

2

1

2

3 WIRE ELECTRET MIC

POSITIVE BIAS

2 WIRE ELECTRET MIC

POSITIVE BIAS

WIRE ELECTRET MIC

NEGATIVE BIAS

SHIELD

BIAS

AUDIO

SHIELD

AUDIO

SHIELD

BIAS

AUDIO

PIN

PIN

PIN

1

2

3

4

5

1

2

3

4

5

1

2

3

4

5

4

3

TA5F

PLUG

4

3

TA5F

PLUG

4

3

TA5F

PLUG

1

5

2

2 WIRE ELECTRET MIC

NEGATIVE BIAS

SLEEVE

1

5

2

TIP

LINE LEVEL

RCA or 1/4 " PLUG

PIN

1

2

1

5

2

DYNAMIC

MIC LEVEL

1

2

3

3

Dynamic LO Z mic or electret with

manufacturers power supply.

SHIELD

AUDIO

SHIELD

AUDIO

SHIELD

Rio Rancho, NM – USA

11

UM250C

TROUBLESHOOTING

Before going through the following chart, be sure that you have a good battery in the transmitter. It is important that
you follow these steps in the sequence listed.

TRANSMITTER BATTERY LED OFF

NO TRANSMITTER MODULATION LEDs

RECEIVER RF LAMP OFF

NO SOUND (OR LOW SOUND LEVEL),
RECEIVER MOD LEVEL LEDs ARE ON

DISTORTED SOUND

SYMPTOM

POSSIBLE CAUSE

1. Battery is inserted backwards.

2. Battery is dead.

1. Gain control turned all the way down.

2. Battery is in backwards. Check power LED.

3. Mic capsule is damaged or malfunctioning.

4. Mic cable damaged or mis-wired.

1. Transmitter not turned on.

2. Transmitter battery is dead.

3. Receiver antenna missing or improperly positioned.

4. Transmitter and receiver not on same frequency. Check switches
display on transmitter and receiver.

5. Operating range is too great.

6. Transmitter antenna not connected

1. Receiver output level set too low.

2. Receiver output is disconnected; cable is defective or mis-wired.

3. Sound system or recorder input is turned down.

1. Transmitter gain (audio level) is far too high. Check modulation
level lamps on transmitter and receiver as it is being used. (Refer
to Operating Instructions for details on gain adjustment.)

2. Receiver output may be mis-matched with the sound system or
recorder input. Adjust output level on receiver to the correct level
for the recorder, mixer or sound system.

3. Excessive wind noise or breath “pops.” Re-position microphone
and/or use a larger windscreen.

4. Transmitter is not set to same frequency as receiver. Check that
frequency select switches on receiver and transmitter match.

HISS AND NOISE -- AUDIBLE DROPOUTS

EXCESSIVE FEEDBACK

12

1. Transmitter gain (audio level) far too low.

2. Receiver antenna missing or obstructed.

3. Transmitter antenna missing.

4. Operating range too great.

1. Transmitter gain (audio level) too high. Check gain adjustment, or
reduce receiver output level, or both.

2. Transmitter too close to speaker system.

3. Mic is too far from user’s mouth.

UHF Belt-Pack Transmitter

SERVICE AND REPAIR

If your system malfunctions, you should attempt to correct or isolate the trouble before concluding that the equipment
needs repair. Make sure you have followed the setup procedure and operating instructions. Check out the intercon­necting cords and then go through the TROUBLESHOOTING section in the manual

We strongly recommend that you do not try to repair the equipment yourself and do not have the local repair shop
attempt anything other than the simplest repair. If the repair is more complicated than a broken wire or loose connec­tion, send the unit to the factory for repair and service. Don’t attempt to adjust any controls inside the units. Once set
at the factory, the various controls and trimmers do not drift with age or vibration and never require readjustment.
There are no adjustments inside that will make a malfunctioning unit start working.

LECTROSONICS service department is equipped and staffed to quickly repair your equipment. In-warranty repairs are
made at no charge in accordance with the terms of the warranty. Out-of-warranty repairs are charged at a modest flat
rate plus parts and shipping. Since it takes almost as much time and effort to determine what is wrong as it does to
make the repair, there is a charge for an exact quotation. We will be happy to quote approximate charges by phone for
out-of-warranty repairs.

RETURNING UNITS FOR REPAIR

You will save yourself time and trouble if you will follow the steps below:

A. DO NOT return equipment to the factory for repair without first contacting us by letter or by phone. We need to know
the nature of the problem, the model number and the serial number of the equipment. We also need a phone number
where you can be reached 8 am to 4 pm (Mountain Standard Time).

B. After receiving your request, we will issue you a return authorization number (R.A.). This number will help speed
your repair through our receiving and repair departments. The return authorization number must be clearly shown on
the outside of the shipping container.

C. Pack the equipment carefully and ship to us, shipping costs prepaid. If necessary, we can provide you with the
proper packing materials. UPS is usually the best way to ship the units. Heavy units should be “double-boxed” for
safe transport.

D. We also strongly recommend that you insure the equipment, since we cannot be responsible for loss of or damage
to equipment that you ship. Of course, we insure the equipment when we ship it back to you.

Mailing address: Shipping address: Telephones:

Lectrosonics, Inc. Lectrosonics, Inc. Regular: [phone]
PO Box 15900 581 Laser Rd. Toll Free [phone]
Rio Rancho, NM 87174 Rio Rancho, NM 87124 FAX: [phone]
USA USA

World Wide Web: http://www.lectrosonics.com Email: [e-mail]

Rio Rancho, NM – USA

13

UM250C

SPECIFICATIONS AND FEATURES

Operating frequencies: 537.600 to 607.900 MHz

614.100 to 767.900 MHz

Frequency selection: 256 frequencies in 100kHz steps

RF Power output: 250 mW

Pilot tone: 32.764 kHz (± 2Hz); 5kHz deviation

Frequency stability: ± 0.002%

Deviation: ± 75 kHz (max)

Spurious radiation: 90 dB below carrier at frequencies less than 1GHz

Equivalent input noise: -126 dBV

Input level: Nominal 2 mV to 300 mV, before limiting.

Mic input greater than 2V, with limiting.
Line input greater than 20V, with limiting (Input to pin 5, pin 4 tied to ground.)

Input impedance: Taps provided for dynamic, electret and line level.

Mic load impedance greater than 4k.
Line load impedance greater than 10k.

Input compressor: Soft compressor, >30 dB range

Gain control range: 43 dB; semi-log rotary control

Modulation indicators: Dual LEDs indicate modulation level 12 dB below limiting and at the onset of limiting.

Controls: 2 position “OFF-ON” slide switch for noiseless turn on/turn off operation. Front panel knob

adjusts audio gain. Recessed control on side panel adjusts low frequency rolloff.
Rotary switches on side panel adjust transmitter frequency.

Audio Input Jack: Switchcraft 5 pin locking (TA5F)

Antenna: Detachable, flexible bronze cable supplied. 50 Ohm port allows connection to test equipment.

Battery: Precision compartment auto-adjusts to accept any known alkaline or lithium 9 Volt battery.

(We’ve tried 150 different ones!)

Battery Life: 2 hours with alkaline, 7 hours with lithium

Weight: 6.6 ozs. including battery

Dimensions: 3.1 x 2.4 x .75 inches

Emission Designator: 160KF3E

14

Specifications subject to change without notice.

UHF Belt-Pack Transmitter

Rio Rancho, NM – USA

15

LIMITED ONE YEAR WARRANTY

LIMITED ONE YEAR WARRANTY

The equipment is warranted for one year from date of purchase against defects in
materials or workmanship provided it was purchased from an authorized dealer. This
warranty does not cover equipment which has been abused or damaged by careless
handling or shipping. This warranty does not apply to used or demonstrator equipment.

Should any defect develop, Lectrosonics, Inc. will, at our option, repair or replace any
defective parts without charge for either parts or labor. If Lectrosonics, Inc. cannot
correct the defect in your equipment, it will be replaced at no charge with a similar new
item. Lectrosonics, Inc. will pay for the cost of returning your equipment to you.

This warranty applies only to items returned to Lectrosonics, Inc. or an authorized
dealer, shipping costs prepaid, within one year from the date of purchase.

This Limited Warranty is governed by the laws of the State of New Mexico. It states the
entire liablility of Lectrosonics Inc. and the entire remedy of the purchaser for any
breach of warranty as outlined above. NEITHER LECTROSONICS, INC. NOR
ANYONE INVOLVED IN THE PRODUCTION OR DELIVERY OF THE EQUIPMENT
SHALL BE LIABLE FOR ANY INDIRECT, SPECIAL, PUNITIVE, CONSEQUENTIAL,
OR INCIDENTAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
THIS EQUIPMENT EVEN IF LECTROSONICS, INC. HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES. IN NO EVENT SHALL THE LIABILITY OF
LECTROSONICS, INC. EXCEED THE PURCHASE PRICE OF ANY DEFECTIVE
EQUIPMENT.

This warranty gives you specific legal rights. You may have additional legal rights which
vary from state to state.

581 LASER ROAD
RIO RANCHO, NM 87124 USA
www.lectrosonics.com

August 24, 2004