Lectrosonics UH200 User Manual

UH200

FREQUENCY-AGILE

PLUG-ON UHF TRANSMITTER

OPERATING INSTRUCTIONS

and trouble-shooting guide

LECTROSONICS, INC.

Rio Rancho, NM

INTRODUCTION

Thank you for selecting the Lectrosonics UH200 frequency agile, plug-on transmitter. The
UH200 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 UH200 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 UH200. Two hundred fifty six frequencies are user selectable in 100kHz steps to alleviate
interference problems in travelling venues.

The UH200 is a rugged, machined aluminum package. Phantom power is provided on pins 2
and 3. Level indicating LEDs are provided to make level settings quick and accurate, without
having to view the receiver. The battery compartment accepts any 9 Volt alkaline or lithium
battery and makes a positive connection via self-adjusting contacts.

Only the UH200 transmitter is covered in this manual. Companion receivers are covered in
separate manuals. The UH200 will operate with any 200 Series Lectrosonics receiver in the
same frequency group.

TABLE OF CONTENTS

INTRODUCTION ..................................................................................................... 2

GENERAL TECHNICAL DESCRIPTION ...............................................................3

CONTROLS AND FUNCTIONS .............................................................................4

OPERATING INSTRUCTIONS .............................................................................. 5

OPERATING NOTES .............................................................................................5

ADJUSTING THE TRANSMITTER FREQUENCY ................................................ 5

TROUBLESHOOTING ............................................................................................6

BATTERY REPLACEMENT ................................................................................... 6

SPECIFICATIONS AND FEATURES ..................................................................... 8

SERVICE AND REPAIR .........................................................................................9

RETURNING UNITS FOR REPAIR .......................................................................9

WARRANTY ........................................................................................... Back cover

The UH200 transmitter is FCC type accepted under Part 74: 470 - 608MHz and 614 - 806MHz

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Frequency Agile Plug-on UHF Transmitter

GENERAL TECHNICAL DESCRIPTION

The UH200 transmitters are comprised of a number of functional
sub-systems as shown in the block diagram below.

GENERAL

The 200 system 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 (6.5 Volts) of battery life. The input amplifier uses an
ultra low noise op amp. 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.

MIC

SHUNT

LIMITER

+5V BIAS
SUPPLY

BUFFER

LIMIT

LED

SET
LED

INPUT
AMP

PEAK AUDIO

INDICATOR &

LIMITER
DRIVER

AUDIO
LEVEL

LP

FILTER

Vref

COMPANDOR

BASS

TREBLE

LP FILTER

HP FILTER

JACK

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. De­emphasis 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 signal 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

±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 4.5
hours of operation using a single 9 Volt alkaline battery. (A 9V
lithium battery will provide over 12 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.

COMPANDED AUDIO

TO XMTR

PILOT
TONE

Vreg

Vreg

OSC

+5VDC

+3.6VDC

MUTE

PWR

+9VDC

PWR

LED

PHASE LOCKED LOOP

DIVIDER

FREQ

SWITCHES

PRESCALER

LOW PASS

FILTER

COMPANDED

AUDIO

VOLTAGE

CONTROLLED

OSCILLATOR

TRANSMITTER

Rio Rancho, NM – USA

UH200 Block Diagram

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