8
SECTION 4
OPERATION
A) Controls and indicators
FM-800 and FM-850: Input level is controled by a stereo (FM-850) potentiometer, labeled
INPUT LEVEL and located on the front panel. Two leds indicate the modulation level:
NORMAL (green), wich lights up when the modulation level is equal of 50% to 100%, wich
indicates a normal modulation state that is required for an undistorted signal at the
receiving end.OVER (red), wich lights up when the modulation level is equal or greater than
101%, wich indicates an overmodulation state and could result in distortion at the
receiving end. The OVER indicator shall never or rarely light, in order to avoid distortion. To
allow a better perception of this indicator, its holding time has been lenghtened, because of
its importance.
The FM-850 transmitter can be switched from mono to stereo mode, in order to let you use
the best mode for your particular application. The stereo selector is located on the front
panel(STEREO). When in stereo mode, the STEREO indicator lights up.In mono mode,
both inputs are active (balanced or unbalanced).
Tuning lock: This indicator (front panel for FM-800 & FM-850 models) will lite up to show
that your choosen FM frequency has been validated and that the RF output is active.A
delay of 3 to 4 seconds is necessary before the system stabilize itself.This delay is
mandatory in a manner to
avoid frequency scrambling while it is in the stabilisation process.
Bass Boost: This control (FM-850 only) when activated,will produce a bass boost of 6dB
from 0Hz to 100Hz.This feature will enhance the bass
response of any type of FM receivers,specialy those that are not equipped
with a bass boost function.
B) Input and output connectors
FM-800 and FM-850 transmitters come with two sets of inputs: RIGHT and LEFT XLR3
balanced inputs and RIGHT and LEFT 1/4" unbalanced inputs, wich are the two most
popular types of input connectors.
The RF output has a female UHF (SO-239) connector and typical load impedance is 50
Ohms. Antenna cable (RG-8 or RG-58) should not exceed 100 feet in lenght for RG-8 and
50 feet for RG-58, in order to minimise the power loss in the cable.
