Lectrosonics UM190b - Manual (Page 7)

UHF Belt-Pack Transmitter
OPERATING INSTRUCTIONS
1) Install a fresh battery according to the instructions on the previous page.
2) Insert the microphone plug into the input jack, aligning the pins; be sure that the connector locks in.
3) Attach the antenna to the jack on the control panel of the unit. Be sure it is screwed in firmly.
3) Turn the power switch to the “ON.”
4) Position the microphone in the location you will use in actual operation.
5) While speaking or singing at the same voice level that will be actually used, observe the AUDIO LEVEL 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 “0dB” LED lights when the
limiter begins to operate. There is over 30dB of limiting range without overload above the “0dB” LED, so it is normal
that the “0dB” LED light up 5% to 10% of the time during use.
6) Once the gain has been adjusted, the transmitter audio can be turned on to make sound system level
adjustments.
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 mic 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 mic 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.
The first LED turns on 20dB below full deviation. The limiting LED turns on at full
deviation and indicates that the input shunt compressor is operating. The input limiter
will handle peaks over 30dB above full modulation, regardless of the gain control
setting. The limiter uses a true absolute value circuit to detect both positive and
negative peaks. The attack time is 5 milliseconds and the release time is 200 milli­
seconds. Occasional limiting is desirable, 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 7