IFBT4-VHF
LECTROSONICS, INC.
10
Installation and Operation
1) The IFBT4 transmitter is shipped with pin 1 of the
XLR input connector tied directly to ground. If a
floating input is desired, a Ground Lift Jumper is
provided. This jumper is located inside the unit on
the PC board near the rear panel XLR jack. For
floating input, open the unit and move the Ground
Lift Jumper to the outermost contacts.
Location of Ground Lift Jumper:
Jumper placed toward PCB as shown connects
pin 1 to ground. Move jumper to outside
contacts to lift ground.
2) Set the MODE switches on the rear panel to match
the specific input source to be used. See Inpout
Configuration (Mode Switches).
3) Insert the power supply plug into the 6-18 VDC
jack on the rear panel.
4) Insert the microphone or other audio source XLR
plug into the input jack. Ensure that the pins are
aligned and that the connector locks into place.
5) Attach the antenna (or antenna cable) to the BNC
connector on the rear panel.
6) Set the OFF/TUNE/XMIT switch to TUNE.
7) Press the MENU button to display the Frequency
Window and adjust the transmitter to the desired
frequency with the front panel Up and Down but-
tons.
8) Position the microphone. The microphone should
be placed where it will be located during actual
use.
9) Use the MENU button to navigate to the Audio
Input Gain Window. While speaking at the same
voice level that will be present during actual use,
observe the audio meter display. Use the Up and
Down buttons to adjust the audio input gain so
that the meter reads close to 0 dB, but only rarely
exceeds 0 dB (limiting).
10) Once the transmitter audio gain has been set, the
receiver and other components of the system can
be turned on and their audio levels adjusted. Set
the power switch on the IFBT4 transmitter to XMIT
and adjust the associated receiver and sound
system level as required.
Note: There will be a delay between the moment
the transmitter is energized and the actual
appearance of audio at the receiver output. This
intentional delay eliminates turn-on thumps, and
is controlled by the pilot tone squelch system.
Adjust Audio Input Level
The AUDIO LEVEL control adjusts the gain applied
to the incoming audio signal. This gain adjustment is
used to match the input level to the incoming signal
from the sound source to provide full modulation and
the maximum signal to noise ratio, not to set the vol-
ume of the associated receiver.
If the audio level is too high
, compression or distor-
tion may occur. The audio level meter will reach the 0
dB level (full scale) frequently or remain indicating full
scale. Input limiting begins when a vertical line ap-
pears at the right end of the level indicator.
Input limiting indicator
If the audio level is too low
, the audio level meter will
continuously indicate a low level. This condition may
cause hiss and noise in the audio, or pumping and
breathing in the background noise.
Low input level
The input limiter will handle peaks up to 30 dB above
full modulation, regardless of the gain control setting.
Occasional limiting is often deemed desirable, indicat-
ing that the gain is correctly set and the transmitter is
fully modulated for optimum signal to noise ratio. Differ-
ent voices will usually require different audio input gain
settings, 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
