Lectrosonics UDR195 User Manual
UDR195UDR195
UDR195
UDR195UDR195
RARA
TIO DIVERSITY RECEIVERTIO DIVERSITY RECEIVER
RA
TIO DIVERSITY RECEIVER
RARA
TIO DIVERSITY RECEIVERTIO DIVERSITY RECEIVER
Wireless Diversity Receiver
OPERAOPERA
OPERA
OPERAOPERA
and trouble-shooting guideand trouble-shooting guide
and trouble-shooting guide
and trouble-shooting guideand trouble-shooting guide
LECTROSONICS, INC.LECTROSONICS, INC.
LECTROSONICS, INC.
LECTROSONICS, INC.LECTROSONICS, INC.
TING INSTRTING INSTR
TING INSTR
TING INSTRTING INSTR
Rio Rancho, NMRio Rancho, NM
Rio Rancho, NM
Rio Rancho, NMRio Rancho, NM
UCTIONSUCTIONS
UCTIONS
UCTIONSUCTIONS
Rio Rancho, NM – USA
1
Table of Contents
INTRODUCTION TO THE 195 SYSTEM ......................................... 4
MODULAR DESIGN ............................................................................................... 4
T195 TRANSMITTER ............................................................................................. 5
M195 TRANSMITTER ............................................................................................ 5
DUAL-BAND COMPANDOR .................................................................................. 5
75KHz DEVIATION ................................................................................................. 5
NO PRE-EMPHASIS/DE-EMPHASIS .................................................................... 5
EXCEPTIONAL THERMAL STABILITY ................................................................. 5
GENERAL TECHNICAL DESCRIPTION ......................................... 6
MODULAR UHF/VHF RF SECTION ...................................................................... 6
SIX-POLE HELICAL RESONATOR FRONT-END ................................................. 6
GaAs FET FRONT-END FILTER COUPLING ....................................................... 6
DOUBLE BALANCED DIODE MIXERS ................................................................. 6
8 POLE LINEAR PHASE FILTER ........................................................................... 6
DIGITAL PULSE COUNTING DETECTOR ............................................................ 7
RATIO COMBINING DIVERSITY WITH OPTI-BLEND .......................................... 7
2:1 EXPANDER (Dual–Band Compandor) ............................................................. 7
VARIABLE CUTOFF LOW PASS FILTER ............................................................. 7
PILOT TONE MUTE (SQUELCH) .......................................................................... 7
FRONT PANEL CONTROLS AND FUNCTIONS ............................ 8
AUDIO OUTPUT LEVEL ......................................................................................... 8
TRANSMITTER AUDIO LEVEL .............................................................................. 8
RF LEVEL INDICATORS ........................................................................................ 8
OPTI-BLEND LEDs ................................................................................................. 8
PILOT LED .............................................................................................................. 9
DIVERSITY MODE ................................................................................................. 9
MONITOR ............................................................................................................... 9
POWER ................................................................................................................... 9
REAR PANEL CONTROLS AND FUNCTIONS ............................. 10
VU METER HEADROOM ..................................................................................... 10
AUDIO OUTPUT ................................................................................................... 10
PHASE REV .......................................................................................................... 10
AC POWER SUPPLIES ........................................................................................ 10
EXTERNAL POWER JACK .................................................................................. 11
CONTACT CLOSURE .......................................................................................... 11
PILOT TONE BYPASS ......................................................................................... 11
ANTENNA JACKS ................................................................................................ 11
2
Wireless Diversity Receiver
ANTENNA USE AND PLACEMENT .............................................. 12
INSTALLATION AND OPERATING INSTRUCTIONS ................... 13
TROUBLESHOOTING ................................................................... 14
POWER SUPPLY AND FUSE .............................................................................. 14
PILOT TONE SQUELCH ...................................................................................... 14
ANTENNAS AND RF SIGNAL STRENGTH ......................................................... 14
AUDIO SIGNAL QUALITY .................................................................................... 15
VU METERING AND OUTPUT LEVEL ................................................................ 15
DR195 REPLACEMENT PARTS and ACCESSORIES................. 15
SPECIFICATIONS AND FEATURES ............................................. 16
SERVICE AND REPAIR ................................................................. 17
RETURNING UNITS FOR REPAIR ................................................ 17
WARRANTY .................................................................... Back cover
Rio Rancho, NM – USA
3
INTRODUCTION TO THE 195 SYSTEM
The DR195 employs the most advanced circuit and mechanical design ever applied to a wireless microphone receiver.
Two independent, ultra-high performance receivers are
blended in a highly effective ratio diversity design. The audio
processing is the finest quality system ever developed for
wireless microphone systems. A unique design of a modular
RF section allows quick frequency changes, yet preserves the
high performance of an advanced fixed frequency design. The
DR195 re-defines the state of the art in high end wireless
microphone receivers.
The entire radio/audio system was designed from a “cold
start,” utilizing all that has been learned thus far. Many new
types of IC’s and semi-conductors are available now that were
only ideas a few years ago. The DR195 design takes advantage of these new devices. The DR195 also takes advantage of
recent changes in the FCC rules and regulations, allowing
wider deviation, which improves the signal to noise ratio and
frequency response of the system dramatically.
The 195 Series system was designed for the most critical
studio and sound reinforcement applications. The system
design represents a significant step forward in wireless
microphone technology. Every stage in the entire audio/radio
chain from transmitter input to receiver output was evaluated
and analyzed to produce the operating parameters and perfor-
mance requirements for this entirely new design. The audio
system provides the lowest distortion and best signal to noise
ratio of any wireless mic system ever built. The RF link is
extremely stable, providing the highest reliability and freedom
from drop outs and interference.
MODULAR DESIGN
The DR195 receiver solves a key problem that has plagued
wireless microphone systems since the first designs were
completed. Most sound reinforcement companies, motion
picture sound mixers, and other traveling users face the
constant need for both highly reliable RF performance and
very high quality audio, while moving from one city or
location to another. Frequency coordination is a constant
struggle in this application in order to work out frequency
groupings for each new location. A frequency switchable
receiver sounds, at first, like it would provide some benefit for
this situation, but the poor RF performance of switchable
designs creates more RF problems than it solves. The “modular” design of the DR195 receiver blends the RF performance
of a fixed frequency design with the flexibility of a switchable
design.
Photo of DR195 and T195
4
Wireless Diversity Receiver
T195 TRANSMITTER
The T195 hand-held transmitter design was the result of
considerable research. The RF and audio performance of the
transmitter was considered first, followed by an analysis of the
typical user’s needs and the practicality of various design
possibilities. The basic circuitry had to accommodate any
frequency in the VHF or UHF spectrums. The mechanical
design had to provide a comfortable “feel,” yet be rugged,
foolproof and easy to operate. The operating features and
functions faced several contradictions in the needs of different
types of users. This led to the development of a very versatile
design wherein the transmitter can be configured for either
“fool proof” operation or to provide user control of the audio
level, metering and indicators. The final T195 design combines the benefits of superior performance, ruggedness , user
convenience, and flexibility.
M195 TRANSMITTER
The M195 is a small belt-pack style transmitter which can be
clipped on the belt, slipped into a pocket, or even taped to the
user's body under clothing. It offers the same high performance and wide deviation as the T195 and is compatible with
all of Lectrosonics' 195 series receivers. The M195 comes
with a standard lavalier microphone but practically any mic
can be adapted to work with this transmitter. The transmitter
audio output can easily be monitored and set from the from
panel.
DUAL-BAND COMPANDOR
Compandors have long been a source of audible distortion in
wireless microphone systems. The basic problem is that when
the full bandwidth of the audio signal is processed by a single
compandor, the attack and decay times will always be a
compromise. If the time constants are fast, high frequency
distortion will be low, however, faster time constants in the
compandor create distortion of lower frequencies. If the time
constants are slowed down, low frequency audio distortion
will be low, but high frequency transients will then be distorted. The 195 system introduces a new approach to solving
this basic problem with compandors, called “dual-band
companding.”
There are actually two separate compandors in the 195 system,
one for high frequencies and one for low frequencies. A
crossover network ahead of the compandor 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 distortion at an extremely
low level. The low frequency compandor uses slower time
constants, reducing low frequency distortion to well below
that of a conventional compandor.
75KHz DEVIATION
75kHz of deviation improves the capture ratio, signal to noise
ratio, and AM rejection of a wireless system dramatically.
NO PRE-EMPHASIS/DE-EMPHASIS
The signal to noise ratio of the 195 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 IF filtering stage
in the receiver, since the high frequencies have been boosted,
which increases the level of the harmonics in the FM signal.
As this signal is passed through the IF filters in the receiver,
distortion will 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 195 system. The dual-band compandor
in the 195 Series system essentially provides a dynamic preemphasis/de-emphasis function with extremely low distortion.
EXCEPTIONAL THERMAL STABILITY
Thermal stability over a wide temperature range is a fundamental requirement for any wireless microphone system
intended for professional use. Thermal drift is a major
problem for some wireless systems that are highly recognized
as “high-end” or “high-performance” products. These systems
actually suffer from thermal drift problems that cause as much
as a doubling or tripling of distortion and as much as 5dB
fluctuations in audio output level as the temperature varies.
If temperature shifts cause the oscillators to drift, or values to
change in the detector, serious distortion will result. The
components in the 195 Series systems meet very stringent
tolerances for thermal drift. System distortion in the 195
series remains at very low levels over a very wide temperature
range. This is especially important in applications where the
receiver and/or transmitter must be operated near heat generating devices, outdoors in direct sunlight, or with the receiver
mounted in an equipment rack.
Rio Rancho, NM – USA
5
GENERAL TECHNICAL DESCRIPTION
The DR195 consists of two high performance, dual-conversion
receivers operating simultaneously. The audio outputs of the
receivers are blended in a ratio controlled by the compared
signal to noise ratios of the receivers. The RF section is
mounted on a separate circuit board, permitting frequency
changes by simply interchanging the RF section assembly.
The RF performance is extremely stable over a very wide
temperature range, making the DR195 perfectly suited to
mounting in studio equipment racks. The proprietary audio
processing includes a dual-band compandor and dynamic
noise filter for very low distortion and a superior signal to
noise ratio. The squelch system is operated by a separate pilot
tone and mutes the audio output directly at the output connector. The audio output is calibrated for exact level matching,
with both peak LED and average VU indicators.
MODULAR UHF/VHF RF SECTION
A unique modular design is employed to simplify frequency
changes. By simply interchanging the RF section module, the
frequency can easily be changed without test equipment or
soldering. All RF stages are contained in the removable RF
section. The output of the RF section is audio, so changes to a
new frequency, even from UHF to VHF, are simply a matter of
changing out the RF module. This modular design provides
the RF reliability of a fixed frequency design and the frequency flexibility of a switchable design.
As a side note, it is important to realize that frequency changes
“on the fly” cannot be made on any type of wireless system.
This is especially true in multi-channel applications where
changing the frequency of one system could produce all kinds
of new intermodulation problems with other systems operating
in the same location. In reality, frequency changes can only be
made on any wireless system during idle periods when the
systems are not in use. For example, if there is a problem with
a transmitter being used on stage that requires a frequency
change, the change cannot be made without interrupting the
program or waiting until there is time between shows.
SIX-POLE HELICAL RESONATOR FRONT-END
The DR195 utilizes dual six-pole helical resonator front-end
filtering, 3 pairs for each receiver. The helical resonators are
much larger than those typically used for wireless microphone
frequencies, producing an extremely high filtering “Q.” The
result is that the DR195 is not affected by high power signals
close to the carrier, and offers extremely high image rejection.
GaAs FET FRONT-END FILTER COUPLING
The DR195 utilizes ultra low noise GaAs FET amplifiers in
the front-end section to compensate for the required losses
between filter stages. The GaAs FET devices are extremely
quiet, especially at the higher frequencies in the UHF band.
DOUBLE BALANCED DIODE MIXERS
A double balanced diode mixer is used in the DR195 to
produce the 10.7 MHz IF signal. The mixer produces output
at only the sum and difference signals, with minimal spurious
signals. This mixer offers a very high overload threshold and
a high degree of isolation between ports.
8 POLE LINEAR PHASE FILTER
The 1st IF amplifier is a 4 stage amp with 2 poles of filtering
after each stage. The filters are high quality, low distortion,
constant group delay ceramic filters. This special type of filter
is needed to accommodate the wide deviation of the 195
system.
RF MODULE
HELICAL
GaAS
HELICAL
GaAS
FET
GaAS
FET
HELICAL
RESONATOR
XTAL
CONTROLLED
1ST
OSCILLATOR
HELICAL
RESONATOR
174-608
mHz
174-608
mHz
RESONATOR
HELICAL
RESONATOR
FET
GaAS
FET
RESONATOR
HELICAL
RESONATOR
Figure 1 - DR195 Block Diagram
6
8 POLE
LINEAR PH ASE
FILTER
IF
AMP
DIODE MIXER
HI-LEVEL
DIODE MIXER
IF
AMP
8 POLE
LINEAR PH ASE
FILTER
HI-LEVEL
455KHZ
BP
FILTER
2ND MIXER
&
IF AMP
XTAL
CONTROLLED
2ND
OSCILLATOR
2ND MIXER
&
IF AMP
455KHZ
BP
FILTER
RF LEVEL
LEDs
RF LEVEL
LEDs
COUNTING
DETECTOR
50 KHZ
LP FILTER
RATIO
COMBINER
&
OPTI-BLEND
50 KHZ
LP FILTER
COUNTING
DETECTOR
23 KHZ
LP
FILTER
2:1
EXPANDER
TREBLE
2:1
EXPANDER
BASS
VARIABLE
CUT-OFF
LP FILTER
AUDIO
AMPLIFIER
PILOT
TONE
MUTE
HEADROOM
ADJUST
OUTPUT
LEVEL
ADJUST
HEADPHONE
OUT
XLR
OUT
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