Lectrosonics H185 User Manual

H185

PLUG-ON TRANSMITTER

OPERATING INSTRUCTIONS

and trouble-shooting guide

LECTROSONICS, INC.

Rio Rancho, NM

INTRODUCTION

Thank you for selecting the Lectrosonics Professional Series wireless microphone system.
This system represents well over 10 years of manufacturing experience in wireless microphones, and

almost 70 years of design experience. It is the best value available today. You will find that the H185
radiates more power than other standard handheld wireless microphones. This provides both greater
operational range, as well as improved signal-to-noise ratio. In addition, the frequency response of the
H185 is flat to 18kHz. This guarantees that the performance of any microphone you choose will not be
degraded by the H185.

If you are new to wireless microphones, you will discover a new freedom of movement and
convenience. If you are an experienced wireless user, you will be pleasantly surprised with the
effortless, quiet performance of the Lectrosonics Professional Series design. Over time, you will
appreciate the rugged dependability of the H185. Superior mechanical design and construction mean
years of trouble-free use.

Only the H185 transmitter is covered in this manual. A matched transmitter/receiver combination
makes up a "system." Receivers are explained in separate manuals.

The H185 transmitter is constructed of metal and operates on interference-free high band frequencies
from 150MHz to 216MHz. Since the H185 uses the actual microphone case as an antenna, there is no
need for any unsightly extra wires. The H185 plugs into the XLR jack of any hand-held microphone,
giving the user the greatest choice of mics.

The H185 transmitter is FCC type accepted under Part 90 (150-172 MHz), and Part 74 (174-216 MHz)

TABLE OF CONTENTS

INTRODUCTION .......................................... 1

GENERAL TECHNICAL DESCRIPTION .......................... 2

CONTROLS AND FUNCTIONS ................................ 3

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

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

TROUBLESHOOTING ....................................... 7

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

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

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

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

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GENERAL TECHNICAL DESCRIPTION

The H185 transmitter is comprised of four major functional subsystems: the input compressor, the mic
preamp/gain control, the compandor, and the RF transmitter (see block diagram below).

The input compressor is a low distortion shunt FET compressor situated before the mic preamp.
Control signals for the compressor are derived after the mic preamp to eliminate any possibility of
overload under any signal condition up to a maximum of 3 Volts input. The range of limiting action
before gross distortion occurs is 20dB.

The mic preamp is an ultra-low noise NE5534 type op-amp. Aside from gain control, this stage also
adds high frequency pre-emphasis to the audio signal. This insures highest signal-to-noise ratios under
varying signal conditions. Gain control is semi-logarithmic to provide smooth gain control action.

The compandor is a high quality audio device that processes the input signal such that large dynamic
ranges of input signal can be transmitted to the receiver without overload or noise. A complementary
system in the receiver recovers the original dynamics of the signal for full audio quality. Compression
and expansion ratios are complementary at 2:1. High frequency pre-emphasis is implemented in the
transmitter to provide another 10dB signal-to-noise ratio improvement. Matching de-emphasis is
provided in all receivers.

The RF transmitter is composed of the crystal stabilized main oscillator followed by a frequency tripler
and two frequency doublers. All three stages are double tuned. Double tuning provides maximum
attenuation of spurious signals, which in turn minimizes the possibility that a transmitter would interfere
with another transmitter/receiver system on another frequency.

All RF stages are biased from a regulated internal source. The output stage has a separate feedback
regulator which not only stabilizes its operating point, but also minimizes AM distortion. These
regulators keep the RF performance consistent from the beginning (9 Volts) to the end (6.5 Volts) of
battery life.

Schematics and alignment instructions will be provided to qualified repair personnel on request.

Figure 1 - H185 Block Diagram

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CONTROLS AND FUNCTIONS

The H185 may be used with a wide variety of microphones. The 3-pin XLR type connector on the
H185 allows the transmitter to be used with any dynamic microphone, as well as many two wire
positive bias lavalier systems (such as those systems supplied by Lectrosonics).

INPUT JACK

Standard 3-pin Switchcraft XLR type. Pin 2 is signal, pin 3 is signal ground, and pin 1 is case ground
(see schematic below). The H185 is self-locking onto a standard microphone. The XLR connector is
permanently bonded to the metal collar, and is not normally replaceable. The electret bias is 5 Volts at
1mA or less. The bias is connected in a "phantom" manner and will not interfere with any standard
balanced microphone. If severe noise is experienced when the microphone is moved with respect to
the H185, the cause is an unbalanced condition between pins 2 and 3 of the microphone.

Figure 2 - Input Jack Schematic

POWER/MUTE SWITCH

Turns the battery power on and off. The center position is an "audio mute" which should be used when
setting the MIC LEVEL control. The "mute" position disconnects the audio signal from the transmitter
and allows you to adjust the audio modulation level without the possibility of feedback. When turning
the transmitter on, pause for a moment in the "mute" position. This will prevent a turn-on surge from
occurring (a "thump" sound).

POWER ON/OFF LED

Glows brightly when battery is good. A weak or dim LED means that the battery is weak, and has
about an hour of operation left. If the LED fails to light, the battery should be replaced. The power
LED should light up in both the "mute" and "on" positions of the POWER/MUTE SWITCH.

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