7
Digital Frequency Agile UHF Hand-held Transmitter
Rio Rancho, NM – USA
HIDING THE POWER LED
This unit has no provision for disabling the LEDs. The audio LEDs are covered
during normal use but the power LED is exposed. If the light is objectionable, we
recommend covering the LED with a piece of tape.
FREQUENCY ADJUST
Two rotary switches (located under the battery door) adjust the center frequency
of the carrier. The Coarse adjustment adjusts the frequency in 1.6 MHz steps
and the fine in 100 kHz steps. Each transmitter is factory aligned at the center of
its operating range for uniform operation across the entire band. The default
position of the frequency select switches is in the center of the transmitter range.
MOD LEVEL LEDs
These LEDs (located under the battery door) indicate the proper setting of the MIC LEVEL control. There are two
bicolor modulation LEDs that can light either red or green.
“-20dB level”
One modulation LED glows green and the transmitter is 20 dB below full modulation.
“-10 dB level”
Both modulation LEDs glow green and the transmitter is close to full modulation.
“+0 dB level”
The -20 LED glows red and the -10 LED glows green.
The transmitter is in slight limiting and is
fully modulated. This is probably desirable. See the discussion below under
Input Limiter
.
“+10 dB level”
Both LEDs are red.
The transmitter is in limiting and you may want to reduce the transmitter audio
gain. See the discussion below under
Input Limiter
.
INPUT LIMITER
The 700 series transmitters employ a digitally-controlled analog audio limiter just before the analog-to-digital con-
verter. The limiter has a range of more than 30dB for excellent overload protection. A dual release envelope makes
the limiter acoustically transparent while maintaining low distortion. It can be thought of as two limiters in series,
connected as a fast attack and release limiter followed by a slow attack and release limiter. The limiter recovers
quickly from brief transients, so that its action is hidden from the listener, but recovers slowly from sustained high
levels, to both keep audio distortion low and preserve short term dynamic changes.
The audio level LEDs indicate limiter activity. The first red LED indicates that the limiter is active and that the trans-
mitter is fully modulated (audio level is b0 and +10 dB). The second red LED indicates that the level is
10dB or more into limiting. Occasional forays into the red are desirable for most applications, since the distortion
introduced by the limiter is so minimal, and full modulation is thus assured. We strongly recommend setting the gain
of the transmitter high enough so that the first red LED occasionally lights.
Generally speaking, some limiting is desirable in normal operation to improve the signal to noise ratio of the system.
The limiting action is not audible and does not create distortion. A highly trained ear would hear only the compres-
sion of the peaks in the audio signal, which is desirable with most recorders and many sound reinforcement systems.
AUDIO LEVEL
This knob (located under the battery door) is operated while speaking or singing into the transmitter to adjust the
audio gain of the transmitter for the correct amount of modulation. The LEDs located next to it indicate the modula-
tion level as the gain is adjusted. See the Operating Instructions section for details on this very important
adjustment.
Coarse Fine
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8 9
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0
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