Listen Technologies LT-700 User manual

Dear Valued Customer,

Thank you for choosing Listen! All of us at Listen are dedicated to providing

you with the highest quality products available. We take great pride in their

outstanding performance because we care that you are completely

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standards and back them with a limited lifetime guarantee. We stand ready

to answer any questions you might have during installation or in the operation

of our products. Should you experience any problems whatsoever with your

Listen products, we are ready to help you in any way we can with prompt,

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have any comments on how we might improve our products or our

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+1.801.233.8992

+1.800.330.0891 North America

+1.801.233.8995 Fax

[email protected]

www.listentech.com

Listen Technologies GmbH

Jasminstr. 16

905 22 Oberasbach, Germany

+49 911 955159 0

Tel

+49 911 955159 40

Fax

www.listentech.de

[email protected]

Thank you and enjoy your listening experience!

%HVWUHJDUGV

Russell Gentner and the Listen Team

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were needed, 99% of all clients indicated that they were happy with repair

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less than 10 days!

Overall client satisfaction of working with Listen was rated 4.8 out of 5.

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Lifetime Warranty – the best in the business!

“Please continue with your excellent attitude toward customer satisfaction. You guys

are great!”

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“You stand behind your product wonderfully.”

The Word Around Listen

Design Guide

LT-700

LR-400/500

Supplementary

Design Guide

FM Technology Overview 5

System Overview 6

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Notes 10

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Quick Reference 19

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3URJUDPPLQJ,QVWUXFWLRQV 

Accessories 28

Notes 29

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%ORFN'LDJUDP 

Quick Reference 40

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Accessories 52

Notes 53

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Frequency Chart 61

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Troubleshooting 63

Frequently Asked Questions 65

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Notes 68

Portable FM Table of Contents

3

Design Guide

Portable FM Design Guide Table of Contents

FM Technology Overview 5

System Overview 6

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Notes 10

5

Design Guide

Frequency Modulation (FM) Technology Overview

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This same technology is used by local FM radio stations to broadcast voice and music. FM signals can travel

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frequency. This section of the manual will help you design a system that will get the best range with the least

amount of interference.

Microphone

FM Transmitter

Receiver

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• Multipath

Multipath interference is a form of RF interference that occurs when radio signals have more than one path

between the receiver and the transmitter causing the two RF signals to add out of phase. This could occur in areas

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and out of squelch when the receiver is moved. Portable applications are much more susceptible to multipath

than those that are stationary. Multipath distortion is often worse as the distance between transmitter and receiver

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VWUDWHJLHVRQHOLPLQDWLQJPXOWLSDWK

• Antenna Positioning

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6

Design Guide

System Overview

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Thus, a person can use a line input source and mic source.

Input Source

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3.5mm Phone Wiring

+ Tip

+ Ring

-

- Sleeve

Unbalanced

Mic input

Line input

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Portable Programmable

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Portable Display FM

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Portable Display FM

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

Design Guide

System Overview

Listen offers two different portable receivers.

Receivers

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Portable Programmable

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Portable Display FM

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na on the unit.

Transmitter

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Portable Display FM

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8

Design Guide

The range of a portable transmission will vary from one application to another. There are many different

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Range varies depending on environment.

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• Move transmitter and receivers away from metal objects.

• Orient both transmitting and receiving antennas vertically.

Key concepts in designing a portable FM system

Use this section of the guide to choose the channel settings for the transmitter and receivers.

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interference free channel.

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the transmitting antenna.

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chart on page 61 to determine the appropriate channels.

Channel Selection

Range

EXAMPLE: 2 channel system use channels 01 & 11

3 channel system use channels 01, 06 & 11

9

Design Guide

Key concepts in designing a portable FM system

As mentioned on page 5, multipath can occur with portable RF systems. The audio quality of the

transmission can decrease with the occurrence of multipath. Here are a few potential improvements that

FDQKHOSLIPXOWLSDWKWDNHVSODFH

Eliminating Multipath

Squelch

Squelching the receiver will mute the audio output when the signal from the transmitter is turned off or

the signal is too weak to be received. Without squelch you would hear radio noise in your earphone with

no RF signal present. “Tightening” the squelch will turn the receiver off if it is chattering because of

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range between transmitter and Receiver.

Transmitter power level

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The lower the power setting, the less range the transmitter will broadcast. Decreasing the broadcast range

will force the receivers to remain closer to the transmitter. To maintain an RF signal, the higher power

settings will increase range between transmitter and receiver thus introducing a higher probability of

multipath.

Multiple Portable Systems

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Squelch

Much like a multipath situation, “tightening” the squelch on the receiver will mute the audio output when

the signal is too weak to be received. Tightening the squelch will help with force the receiver to squelch

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Transmitter power level

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power could help decrease the amount of interference if there are many frequencies being used in the

vicinity.

Spacing of channels

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channels further from each other.

DX/Local

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PRUHVHQVLWLYHWKDQ';

10

Design Guide

Notes

11

Design Guide

Notes

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