Lectrosonics UM700 User manual

UM700
DIGITAL FREQUENCY-AGILE
UHF BELT-PACKTRANSMITTER
LECTROSONICS, INC.
Rio Rancho, NM
www.lectrosonics.com
OPERATING INSTRUCTIONS
and trouble-shooting guide

2
TABLE OF CONTENTS
The UM200C transmitter is FCC type accepted under Part 74: 470-608MHz and 614-802MHz
INTRODUCTION.................................................................................................. 3
GENERAL TECHNICAL DESCRIPTION ............................................................ 4
CONTROLS AND FUNCTIONS .......................................................................... 6
BATTERY INSTALLATION ................................................................................... 8
OPERATING INSTRUCTIONS ............................................................................ 8
OPERATING NOTES ........................................................................................... 9
ADJUSTING THE TRANSMITTER FREQUENCY.............................................. 9
MICROPHONE CORD TERMINATION ............................................................. 10
5-PIN INPUT JACK WIRING ............................................................................. 11
A6U UHF ANTENNA.......................................................................................... 13
TROUBLESHOOTING ....................................................................................... 14
SPECIFICATIONS AND FEATURES................................................................. 15
SERVICE AND REPAIR..................................................................................... 16
RETURNING UNITS FOR REPAIR................................................................... 16
WARRANTY .........................................................................................Back cover

3
Frequency Agile UHF Belt-PackTransmitter
Rio Rancho, NM – USA
INTRODUCTION
The 700 Series wireless system was designed to take advantage of the superior
audio performance provided by DSP audio signal processing and the security
provided by proprietary digital and encrypted digital radio operation.
Several advantages are provided by a digital wireless system and DSP technology:
• A digital radio system provides outstanding signal to noise ratio
• The signal to noise ratio of a digital radio system does not vary with the RF signal
strength arriving at the receiver.
• DSP audio signal processing provides a superior limiter
• Eavesdropping is difficult and secure encryption techniques can be implemented
The UM700 is a rugged, machined aluminum package in a belt-pack configuration
with a removable, spring loaded belt clip. A 5-pin input jack provides taps for any
microphone or line level signal. The unit is powered by a single 9 Volt alkaline or
lithium battery, or from external DC using an optional battery eliminator. The an-
tenna is a detachable, locking 1/4 wavelength flexible bronze alloy cable that con-
nects to a 50 Ohm SMA port on the control panel.
Only the UM700 transmitter is covered in this manual.Companion receivers are
covered in separate manuals. The UM700 will operate with any 700 Series Lec-
trosonics receiver in the same frequency block.

4
UM700
Block Diagram
5
4
3
2
1
Freq
Switches
Shunt
Limiter From
DSP
LF
Roll-Off
Preamp and
Supersonic
Filter Audio
Gain
+5V Bias
Supply
Mic
Jack Buffer and
Lo Freq
Filter
Analog to Digital
Converter Digital Signal
Processor
To uP
Modulator
Drive
Amp Power Amp
12
3
1/4 Wave
Antenna
50
Audio
Level
Oscillator
Filter
Synthesizer
To
uP
uP
EEProm
Multicolor
Audio Level
LEDs
Multicolor
Battery Status
LED
Switching
Pwr Supply
Delay Control
from uP
9V
Polarity
Protection
Diode Power
Switch 4V Main
Pwr Supply
Isolator
GENERAL TECHNICAL DESCRIPTION
GENERAL
The 700 Series wireless system uses digital modulation for an extremely high signal to noise ratio and freedom from
distortion and compandor artifacts. The input preamplifier uses an ultra low noise op amp for an excellent signal to
noise ratio. A dual-envelope limiter is implemented by the DSP firmware to cleanly limit input signal peaks up to
30dB above full modulation. The transmitter circuits are all regulated to allow full output power from the beginning (9
Volts) to the end (5.5 Volts) of battery life.
The UM700 transmitter is comprised of a number of functional sub-systems as shown in the block diagram below.
DIGITAL MODULATION
Digital modulation is used to eliminate compandor artifacts and provide an extremely high signal to noise ratio. A
proprietary compression algorithm is used to contain the RF energy into a narrower bandwidth than other digital
systems to allow the 700 Series system to utilize frequencies in FCC Part 74 for broadcast and motion picture
production. For applications that require secure operation that prevent eavesdropping, encryption can easily be
implemented.
AUDIO PROCESSING
The input circuitry includes an adjustable low frequency roll-off filter ahead of the limiter and gain stage to customize
the low frequency response for varying conditions. In controlled environments with minimal low frequency ambient
noise, such as a film production set, the frequency response can be extended to 30 Hz. For applications with
excessive low frequency energy, such as in a moving vehicle or rooms with HVAC noise, the low end can be rolled
off as high as 150 Hz to reduce the effects of the noise.
A “dual-envelope”limiter with 30 dB of range is next in the signal chain. This special limiter is software controlled,
being driven by the DSP to minimize “overshoot”and slow attack times that can occur in other types of limiter circuits.
The compressor works with two different time constants to cleanly handle a wide variety of dynamics. A fast peak
limiter prevents overload distortion from sharp, infrequent transients in the audio signal, and an averaging limiter with
longer time constants prevents “pumping”(gain modulation) that can occur with repeated peaks that are closely
spaced. Supersonic filtering is provided to prevent excessive high frequency energy from entering the A/D converter.

5
Frequency Agile UHF Belt-PackTransmitter
Rio Rancho, NM – USA
A/D CONVERTER AND DSP PROCESSOR
The processed audio signal enters the A/D converter to generate a digital signal for the modulator. A proprietary
algorithm is used for sampling and compression to minimize noise and distortion, and provide a wide, flat frequency
response. The signal then enters the modulator to generate a digitally modulated radio signal.
OUTPUT SECTION
Intermodulation (IM) occurs in the final amplifier stages of conventional transmitters when the transmitters are within
a few feet of each other. This can create serious problems in multi-channel wireless systems when an IM signal falls
on the carriers, IF frequencies, etc.of the systems being operated. To eliminate this problem in the UM700, the
modulated radio signal passes through a circular isolator before entering the antenna. The circular isolator functions
like a “one-way check valve”to allow the RF signal to pass through to the antenna, but not to pass backwards into
the amplifier stage. RF signals from other nearby transmitters cannot reach the output amplifier in the UM700. This
provides excellent stability and eliminates IM in the output stage of the transmitter.
LONG BATTERY LIFE
High efficiency circuits and switching power supplies throughout the design allow over 4.5 hours of operation using a
single 9 Volt alkaline battery. (A 9V lithium battery will provide over 14 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
700 Series wireless systems are available on eight different “blocks”of 256 frequencies, from 537.600 to 767.900
MHz. Each of these blocks provides 256 selectable frequencies in 100 kHz steps over a 25.6 MHz bandwidth. This
wide variety of selectable frequencies alleviates carrier interference problems in mobile or traveling applications. Two
16-position rotary switches on the side panel of the unit are used to select the frequency.
The UM700 transmitter section uses a synthesized, frequency selectable main oscillator The frequency is extremely
stable over a wide temperature range and over time.
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 UM700 consists of a flexible 1/4
wavelength bronze cable, detachable via an SMA connector. The impedance of this connector is 50 Ohms.

6
FREQUENCY
1.6MHz 100kHz
BLK 20 (BK)
512.0 - 537.5
SN:
XXXX
35 150
75 Hz
LF ROLL OFF
FCCID:DBZUM700
Lectrosonics, Inc.
Made in U.S.A.
LECTROSONICS
UM700
OFF ON
LEVEL
AUDIO
ANTENNA
CONTROLS AND FUNCTIONS
INPUT JACK
The input jack on the UM700 is a Switchcraft TA5M connector that accommodates virtually every lavalier, hand-held
or shotgun microphone available, with positive or negative bias. The input will also cleanly handle line level signals
up to 300 mV before limiting. Use a Switchcraft TA5F connector on the microphone cable or input adapter cord .
See the separate sheet titled “Transmitter 5-Pin Input JackWiring” regarding the correct connections for
various microphones, and other sources.
ON/OFF SWITCH
Turns the battery power on and off. Even when the switch is turned off or on abruptly, the digital muting prevents
“thumps”or transients from occurring.
“ON” LAMP
Glows brightly when the battery is good and the ON/OFF switch is ON. This tri-color LED will indicate the condition
of the battery in the transmitter as follows:
Green - battery good
Yellow - battery getting low
Red - battery very low - change now
Blinking Red - battery critical - failure imminent
FREQUENCY ADJUST (located under the sliding door)
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 of
the frequency select switches is in the center of the transmitter’s range.
Since the internal circuits are all tightly regulated and the RF output stage is powered by a regulated supply, the
transmitter will continue to operate perfectly to a battery voltage of 5.5Volts.
Please note that a weak battery will sometimes light the POWER LED
immediately after turn on, but will soon discharge to the point where the
LED will indicate a weak battery, just like a flashlight with “dead” batteries.
The combination of an accurate battery condition indicator and regulation of all
internal circuits provides much longer battery life, as well as consistent perfor-
mance over the life of the battery.
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F

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Frequency Agile UHF Belt-PackTransmitter
Rio Rancho, NM – USA
AUDIO LEVEL CONTROL
Used to adjust the audio input level for proper modulation.
AUDIO LEVEL LEDS
Indicate the proper setting of the MIC LEVEL control.
The two audio level LED’s are bi-colored (red/.green) and indicate 5 levels -
Off - Off no audio modulation
Green - Off low audio
Green - Green moderate audio
Yellow -Yellow full audio
Red - Red limiting
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 pre-cut lengths
for specific frequency blocks, or as a kit with instructions to cut the antenna for any frequency block.
ADJUSTABLE LOW FREQUENCY ROLL-OFF
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 reduce the undesirable effects of very low frequency audio often pro-
duced by air conditioning systems, automobile traffic and other sources. Excessive low frequency content in the
audio input can cause overload 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 sys-
tems. A common example is wind blowing across a microphone, causing very high levels of low frequency audio
(“wind noise”). By rotating the roll-off control clockwise, the hinge point of the roll-off is increased to reduce the level
of low frequencies. In low noise 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.
USE ONLYTHE SCREWTHAT IS SUPPLIED
The circuitry is tightly packed into this unit. A longer screw will permanently damage the transmitter! Use only
Lectrosonics PN:28528 which is a Phillips head, 4-40 x 3/16", FL100 screw.

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BATTERY INSTALLATION
The transmitter is powered by a standard alkaline or lithium 9 Volt battery. It is important that you use ONLY an
ALKALINE or 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 1.5 hours of operation, or less, and will
run down quite abruptly. Unless it is cold, alkaline batteries provide over 4.5 hours of operation. Lithium batteries
can be used to provide up to 14 hours. 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 alkaline 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.
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
lights as you speak.
Swing the
door open
Press outward on the
battery door in this
direction

9
Frequency Agile UHF Belt-PackTransmitter
Rio Rancho, NM – USA
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 be Red frequently or stay Red. This condition may reduce the dynamic
range of the audio signal.
If the audio level is too low —neither LED will light, or only one LED will flicker Green. This condition will reduce the
signal to noise ratio of the system.
The input limiter will handle peaks up to 30dB above full modulation. 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 fingerrnail.
The UDR700 receiver front panel will indicate the correct switch settings to match the receiver frequency.
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F

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MICROPHONE CORD TERMINATION
1
23
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