Lectrosonics IFBT5 User Manual download pdf (Page 7)

IFB Transmitter

INSTALLATION AND OPERATION

1) Pin 1 of the XLR input jack is normally tied directly to ground inside the unit. If a floating connection is desired,

move the ground lift jumper inside the unit. (See next page for the location of the ground lift jumper.)

2) Set the MODE switches on the rear panel to match the specific input source to be used. (See next page for details

on setting the MODE switches.)

3) Insert the power supply plug into the 12VDC jack on the rear panel.

4) Insert the microphone plug into the input jack, aligning the pins; be sure that the connector locks in.

5) Attach the antenna to the BNC connector on the rear panel.

6) Mute the sound system.

7) Turn the transmitter power switch to the “TUNE” position.

8) Adjust the transmitter to the desired frequency with the FREQ up and FREQ down buttons on the front panel.

Each push changes the frequency by 100 or 25 kHz and if the button is held down the frequency will automati-

cally change at a slow rate of 1 channel per second. If the button is held down for more than 5 seconds the

frequency will automatically increase and decrease at a faster rate of about 5 channels per second.

9) Position the microphone in the location you will use in actual operation.

10) While speaking at the same voice level that will actually be used, observe the MODULATION LEDs. Adjust the

AUDIO LEVEL control knob until the LEDs begin to light. Start at a low setting where neither LED lights as you

speak. Gradually, turn the gain up until one LED lights, then the other. The -20 LED lights when the audio level is

about 20dB below full modulation. The “0” LED lights when the limiter begins to operate. There is over 15dB of

limiting range without overload above the “0” LED. It is desirable that it lights up 5-10 percent of the time during

use.

11) Once the gain has been adjusted, the audio system audio can be turned on to make level adjustments. Set the

power switch to the XMIT position and adjust the receiver and/or sound system level as required. Please note,

there will be a delay between the moment the switch is thrown and the time when audio will actually appear at

the receiver output. This intentional delay eliminates turn on thumps, and is controlled by the pilot tone squelch

control.

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 to the appropriate input level.

If the audio level is too high — both LEDs will light frequently or stay lit. This condition may reduce the dynamic range

of the audio signal.

If the audio level is too low — neither LED will light, or the -20 LED will light dimly. This condition may cause hiss and

noise in the audio, or pumping and breathing in the background noise.

The “-20” LED turns on approximately 20dB below full deviation. The “0” LED turns on at full deviation and indicates

that the input shunt compressor is operating. The input limiter will handle peaks over 15dB above full modulation,

regardless of the gain control setting. The limiter uses a true absolute value circuit to detect both positive and nega-

tive peaks. The attack time is 5 milliseconds and the release time is 200 milliseconds. Occasional limiting is desir-

able, indicating that the gain is correctly set and the transmitter is fully modulated for optimum signal to noise ratio.

Different voices will usually require different settings of the AUDIO LEVEL control, so check this adjustment as each

new person uses the system. If several different people will be using the transmitter and there is not time to make the

adjustment for each individual, adjust it for the loudest voice.

Rio Rancho, NM – USA

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Lectrosonics IFBT5 User Manual Page 7

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