SR175
COMPACT RECEIVER
OPERATING INSTRUCTIONS
and trouble-shooting guide
Digital Code Squelch
LECTROSONICS, INC.
Rio Rancho, NM
INTRODUCTION
The SR175 is a fixed frequency, crystal controlled receiver designed for use in public address
applications. A proprietary Digital Code Squelch* is used in the system design to eliminate squelching
problems caused by interference. The compact size of the receiver permits mounting the receiver
almost anywhere. The audio output is a balanced XLR type, variable in level, to match any type of
sound system.
The digital code system provides much more reliable control over the receiver audio output than a
conventional squelch can provide. The matching transmitter generates an 8-bit code at turn on, and
another code at turn off, to open and close the audio output on the receiver. The squelch on the
receiver cannot be opened by anything other than the specific code it is programmed to receive. This
type of squelch system is even more important when the receiver is connected into an automatic mixing
system.
The SR175 circuitry utilizes the latest surface mount technology, with significant oscillator shielding. Up
to four systems can be operated simultaneously in close proximity in the 169 to 172 MHz band without
intermodulation, crosstalk or squelch problems. The housing is a durable aluminum extrusion with
rugged connectors for lasting reliability.
TABLE OF CONTENTS
INTRODUCTION .......................................... 1
RECEIVER FRONT PANEL ................................... 2
RECEIVER REAR PANEL .................................... 3
SYSTEM SETUP AND OPERATION ............................ 4
INDICATORS ............................................. 4
ANTENNA USE AND PLACEMENT ............................. 5
TROUBLESHOOTING ....................................... 6
REPLACEMENT PARTS and ACCESSORIES ..................... 6
SERVICE AND REPAIR ..................................... 7
RETURNING UNITS FOR REPAIR ............................. 7
SR175 SPECIFICATIONS AND FEATURES ....................... 8
WARRANTY ....................................... Back cover
1
RECEIVER FRONT PANEL
OUTPUT
POWER
LECTROSONICS
SR175
LEVEL LIMIT CODE
DIGITAL
CODE
OFF ON
LEVEL and LIMIT LEDs - Indicates the modulation (audio level) of the incoming signal - see
transmitter manual for proper adjustment of transmitter "MIC LEVEL" or "GAIN." The LEVEL lamp
should flicker, or stay lit as you speak into the microphone. The LIMIT lamp is a "peak" indicator
showing that the audio level in the transmitter is being limited. It is normal to see an occasional flicker
of the LIMIT lamp.
POWER OFF-ON Switch - This slide switch turns the power off and on.
POWER LED - Glows when the switch is in the "ON" position and the power source is good, or when
the AC adapter is properly connected. If this LED is very dim or does not light up when the switch is
turned on, check the power source.
CODE LED - Lights when the transmitter is turned on and the internal code in the transmitter matches
this particular receiver. If the receiver is turned on after the transmitter, the code led will not come on.
In this case, it will be necessary to turn the transmitter off and back on to enable the receiver. When
the carrier signal from the transmitter is too weak to produce a clean audio signal the receiver will
squelch (no audio) but the code lamp will remain lit.
OUTPUT - An attenuator used to regulate the output level of the receiver. When fully counterclockwise, the output of the XLR jack on the rear panel will be the same as a typical microphone. Fully
clockwise, the output level will be similar to a high output electret microphone. Intermediate settings
are often necessary to ideally match the level with other equipment.
Figure 1 -SR175 Front Panel
2
RECEIVER REAR PANEL
ANT 12V DC
IN
AUDIO OUT
1
2
3
ANT terminal - A standard BNC connector compatible with the supplied antenna.
12 VDC IN - Connect the power supply here - the CH-12 AC adapter is supplied with the receiver for
powering the unit from a 110V AC source. The receiver may also be powered from 12 volt DC sources
using the correct plug (Switchcraft S-760 power plug); the center pin on the receiver jack is positive (+).
AUDIO OUT (standard XLR jack) - This is the audio output that should connect into your sound system.
Being such a common type of connector, many different adapters and cords are available from local
audio or electronics dealers in your area, or from the factory. The pin configuration is:
Pin 1 - shield
Pin 2 - Audio (+)
Pin 3 - Audio (-)
Figure 2 - SR175 Rear Panel
3
SYSTEM SETUP AND OPERATION
1) Connect the supplied CH-12 to the power jack on the rear panel.
2) Attach the antenna.
3) Connect the audio cable.
XLR Output: Pin 1 - ground
Pin 2 - audio (+)
Pin 3 - audio (-)
4) Set front panel switch to "ON."
Check to see that the red POWER LED lights up.
5) Adjust transmitter "GAIN."
This is perhaps the most important step in the set up procedure. (see your transmitter manual
for specific instructions on the proper gain adjustment of your transmitter)
6) Adjust audio OUTPUT level control according to the type of input on your equipment. The input
levels on different equipment vary which may require that you set the OUTPUT control in an
intermediate position of the control. Try different settings and listen to the results. If the output of
the receiver is too high, you may hear distortion or a loss of the natural dynamics of the audio
signal. If the output is too low, you may hear steady noise (hiss) along with the audio.
Note: Do not use the transmitter GAIN control to adjust the loudness of
your sound system.
INDICATORS
CODE - This red LED lights up when the transmitter is turned on. This indicates that the receiver is
getting an adequate RF signal (carrier) from the transmitter and that the code from the transmitter
matches the preset code embedded in the receiver.
POWER - This red LED lights up when the receiver is properly connected to a power supply and
switched on.
LEVEL and LIMIT - The red LED (marked LEVEL) lights up when an audio signal is present at an
adequate level to produce a good signal to noise ratio. The red LED (marked LIMIT) lights up when
the audio level is being compressed in the transmitter. An extremely high audio level may also cause
distortion.
REVIEW THE TRANSMITTER INSTRUCTION MANUAL FOR PROPER ADJUSTMENT
AND SETUP OF THE TRANSMITTER MIC LEVEL
4
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DIRECT SIGNAL
INDIRECT SIGNAL
ANTENNA USE AND PLACEMENT
REFLECTIVE SURFACE
D
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TRANSMITTER
PHASE
LECTROSONI CS
SR175
RECEIVER
CANCELLATION
MULTI-PATH DROPOUT
Connect the antenna to the rear panel jack. Extend the antenna fully if you are using a telescoping
type. Position the antenna so that it is not touching or within 3 or 4 feet of large metal surfaces. It is
also good practice to position the receiver so that there is a direct "line of sight" between the transmitter
and the receiver antenna.
A wireless transmitter sends a radio signal out in all directions. This signal will often bounce off nearby
walls, ceilings, etc. and a strong reflection can arrive at the receiver antenna along with the direct
signal. If the direct and reflected signals are out of phase with each other a cancellation may occur.
The result would be a "dropout." A dropout sounds like either audible noise (hiss), or in severe cases,
may result in a complete loss of the sound when the transmitter is positioned in certain locations in the
room. A dropout normally sounds like "hum" or "hiss." Moving the transmitter even a few inches will
change the sound of the hum or hiss, or eliminate it. A dropout situation may be either better or worse
as the crowd fills and/or leaves the room.
In the event that you do encounter a dropout problem, first try moving the receiver/antenna at least 3 or
4 feet from where it was. This may alleviate the dropout problem. If dropouts are still a problem, try
moving the receiver and/or the antenna to an entirely different location in the room.
Lectrosonics transmitters radiate more power, and the receivers are more sensitive than any other on
the market. This reduces dropouts to an insignificant level. If, however, you do encounter dropouts
frequently, call the factory. There is probably a simple solution.
5
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.
SYMPTOM POSSIBLE CAUSE
TRANSMITTER BATTERY LED OFF 1) Battery is inserted backwards.
2) Battery is dead.
RECEIVER CODE LAMP OFF 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
labels on transmitter and receiver.
5) Transmitter and receiver do not have the same internal
code. Check labels on transmitter and receiver.
5) Operating range is too great.
NO SOUND BUT RECEIVER MOD
LEVEL LEDs ARE ON 1) Receiver audio output is disconnected or cable is
defective or mis-wired.
2) Sound system or recorder input is turned down.
DISTORTED SOUND 1) Transmitter gain (MIC LEVEL) is too high. Speak or sing
into the transmitter and check mod level lamps on the
receiver.
2) Receiver output may be mis-matched with the sound
system or recorder input.
3) Excessive wind noise or breath "pops." Use windscreen
or re-position the microphone.
HISS AND NOISE - AUDIBLE DROPOUTS 1) Transmitter gain (MIC LEVEL) too low.
2) Receiver antenna missing or obstructed.
3) Operating range too great.
EXCESSIVE FEEDBACK 1) Transmitter gain (audio level) too high. Check gain
adjustment and/or reduce receiver output.
2) Transmitter too close to speaker system.
3) Transmitter too far from the user’s mouth.
REPLACEMENT PARTS and ACCESSORIES
Part No. Description
CH-12 110 Volt AC adapter for SR170AC receiver
A-185BNC Telescoping, swivel-mount antenna with BNC plug
A-170AC Straight whip antenna with BNC plug
A-200 Dipole antenna with dual whips & aluminum base
M119-MICRO Lavalier microphone, omni-directional pattern
M140-MICRO Lavalier microphone, cardioid pattern
6
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 inter-connecting cords and then go through the TROUBLE SHOOTING
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. (505) 892-4501
PO Box 15900 581 Laser Rd. (800) 821-1121
Rio Rancho, NM 87174 Rio Rancho, NM 87124 FAX: (505) 892-6243
USA USA
7
SR175 SPECIFICATIONS AND FEATURES
Operating Frequencies:
RF Sensitivity:
IF Selectivity:
Squelch Quieting:
AM Rejection:
Modulation Acceptance:
Third Order Intercept:
Distortion:
Signal/Noise Ratio:
Audio Outputs:
Antenna Input:
Controls:
169 to 186 MHz, crystal controlled
-110 dBm for 20 dB Sinad (0.7 uV)
150 kHz interference bandwidth
-30 dB @ ±200 kHz
-109 dB
Below the noise at all input levels
±15 kHz
+5 dBM
0.5% @ 1 kHz, 12 kHz deviation (system)
-90 dB (system)
XLR: 200 Ohms bal; 100 mV max.
BNC; 50 Ohms impedance
Front panel attennuator controls XLR output
2 position power/function switch
Indicators:
Power Requirements:
Power Consumption:
Weight:
Dimensions:
Red LED for power ON
2 LEDs for mod level
Red LED for CODE ON
12 Volts DC external, polarity protected
110 Volts AC via CH-12 AC adapter
70 mA @ 12 kHz deviation, 61 mA @ idle
11 ounces
1.1 x 2.75 x 5.5 inches
8
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, we will, at our option, repair or replace any
defective parts without charge for either parts or labor. If we cannot
correct the defect in your equipment, we will replace it at no charge
with a similar new item. We will pay for the cost of returning your
merchandise to you.
This warranty applies only to items returned to us, shipping costs
prepaid, within one year from the date of purchase.
This warranty gives you specific legal rights. You may have additional
legal rights which vary from state to state.
LECTROSONICS, INC.
581 LASER ROAD
RIO RANCHO, NM 87124 USA November 10, 1994
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