LM400 FREQUENCY-AGILE UHF BELT-PACK TRANSMITTER OPERATING INSTRUCTIONS and trouble-shooting guide LECTROSONICS, INC. Rio Rancho, NM www.lectrosonics.
LM400 TABLE OF CONTENTS INTRODUCTION ..................................................................................................... 3 GENERAL TECHNICAL DESCRIPTION ............................................................... 4 CONTROLS AND FUNCTIONS ............................................................................. 6 BATTERY INSTALLATION ..................................................................................... 8 OPERATING INSTRUCTIONS .......................................
Frequency-Agile UHF Belt-Pack Transmitter INTRODUCTION Thank you for selecting the Lectrosonics LM400 frequency agile, belt-pack transmitter. The LM400 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 LM400 was the direct result of numerous conversations with users, staging and touring companies and dealers across the US.
LM400 GENERAL TECHNICAL DESCRIPTION GENERAL The 400 system uses 75kHz wide deviation for an extremely high signal to noise ratio. The switching power supplies provide constant voltages to the transmitter circuits from the beginning (9.3 Volts) to the end (5.5 Volts) of battery life. The input amplifier uses an ultra low noise op amp for quiet operation. It is gain controlled with a wide range dual envelope input compressor which cleanly limits input signal peaks over 30dB above full modulation.
Frequency-Agile UHF Belt-Pack Transmitter Channel noise still has an impact on received signal quality and will eventually overwhelm the receiver. The Digital Hybrid simply encodes the signal to use a noisy channel as efficiently and robustly as possible, yielding audio performance that rivals that of wholly digital systems, without the power and bandwidth problems inherent in digital transmission. As always, these advantages come at a cost.
LM400 CONTROLS AND FUNCTIONS LECTROSONICS LM400 MIC AUDIO LEVEL -10 -20 FREQUENCY E D C B A F 0 1 2 3 4 5 9 8 7 6 1.6MHz E D C B A F 0 1 2 3 4 5 9 8 7 6 100kHz ON OFF ANTENNA MIC The Microplug (2.5 mm) input on the transmitter accommodates 2 wire positive bias lavalieres. This jack will mate with a Switchcraft 850 plug. ON/OFF SWITCH Turns the battery power on and off.
Frequency-Agile UHF Belt-Pack Transmitter INPUT LIMITER The 400 series transmitters employ a digitally-controlled analog audio limiter just before the analog-to-digital converter. The limiter has a range of more than 30dB for excellent overload protection. A dual release envelope makes the limiter acoustically transparent while maintaining low distortion. It can be thought of as two limiters in series, connected as a fast attack and release limiter followed by a slow attack and release limiter.
LM400 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 “longlasting” are not adequate. Ni-cad rechargeable batteries will only provide 1.5 hours of operation, or less, and will run down quite abruptly. Alkaline batteries provide over 6 hours of operation at room temperature.
Frequency-Agile UHF Belt-Pack Transmitter 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 red LEDs will light frequently or stay lit. This condition may reduce the dynamic range of the audio signal.
LM400 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. NO TRANSMITTER MODULATION LEDs 1) 2) 3) 4) RECEIVER RF LAMP OFF 1) 2) 3) 4) NO SOUND (OR LOW SOUND LEVEL), RECEIVER INDICATES PROPER AUDIO MODULATION 1) Receiver output level set too low.
Frequency-Agile UHF Belt-Pack Transmitter SPECIFICATIONS AND FEATURES Operating frequencies: 537.600 to 607.900 MHz 614.100 to 793.500 MHz Frequency selection: 256 frequencies in 100kHz steps RF Power output: 60 mW (nominal) Pilot tone: 25 to 32 kHz frequency; 5kHz deviation Frequency stability: ± 0.002% Deviation: ± 75 kHz (max) Spurious radiation: 60 dB below carrier Equivalent input noise: –120 dBV, A-weighted Input level: Nominal 2 mV to 300 mV, before limiting.
LM400 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 interconnecting cords and then go through the TROUBLESHOOTING 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.
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LIMITEDONE ONE YEAR YEAR WARRANTY LIMITED 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, Lectrosonics, Inc.
