Diagnostics; Pilot Tone Bypass - Lectrosonics DCR822 Instruction Manual

DCR822

Diagnostics

Multi-channel System Checkout
Interference can result from a wide variety of sources
including TV station signals, other wireless equipment in
use nearby, or from intermodulation within a multi-chan-
nel wireless system itself. Regardless of how the frequen-
cies were coordinated, a final checkout procedure is
always a good idea.
Scanning with the RF spectrum analyzer built into the
DCR822 system will identify external RF signals, but it
does not address the compatibility of the selected fre-
quencies.
The pre-coordinated frequencies address in-system in-
termodulation, but obviously cannot take into account RF
signals from external sources that may be present in the
location where the system will be operating.
1. Set up the system for testing.
Place antennas in the position in which they will be
used and connect to the receivers. Place trans-
mitters about 3 to 5 feet apart, about 25 to 30
feet from the receiver antennas. If possible, have
all other equipment on the set, stage or location
turned on as well, especially any mixing or record-
ing equipment that will be used with the wireless
system.
2. Set all receivers on clear channels.
Turn on all receivers, but leave the transmitters
off. Observe at the RF signal strength indicator for
each receiver module. If a signal is present, change
the frequency to a clear channel where no signal
is indicated. If a completely clear channel cannot
be found, select the frequency with the lowest RF
level indication. Once all receiver modules are on
clear channels, go to step 3.
3. Turn each transmitter on one at a time.
Start with all transmitters turned off. As you turn on
each one, look at the matching receiver to verify a
strong RF signal is received. Then, look at the other
receivers and see if one of them is also picking up
the signal. Only the matching receiver should indi-
cate a signal. Change frequencies on either system
slightly until all channels pass this test, then check
again to see that all channels are still clear as done
in step 2.
4. Turn each transmitter off one at a time.
With all transmitters and receivers turned on, turn
each transmitter off one at a time, in turn, and look
at the RF level indicator on the matching receiver
module. The RF level should disappear or drop to
a very low level. If it does not, change frequency on
that receiver and transmitter and try it again. When
a clear frequency is found, turn the transmitter on
and move on to the next channel.
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IMPORTANT: Any time a frequency is changed
on any of the systems in use, you must start at
the beginning and go through this procedure
again for all systems. With a little practice, you
will be able to do this quickly and save yourself
some "multi-channel grief."

Pilot Tone Bypass

Hybrid compatibility modes (NU Hyb, EU Hyb, etc.) use
a supersonic "pilot tone" to control the squelch (audio
mute) of a receiver module to keep it silent until a valid
signal is received. When a signal with the correct pilot
tone is received, the squelch opens and audio is deliv-
ered to the output. Pilot tone squelch control also elimi-
nates transients (clicks and pops) when transmitters are
turned on and off.
Pilot tone control can be bypassed as a diagnostic tool.
Bypass opens the audio output of the receiver uncondi-
tionally, allowing you to listen to any signals entering the
receiver to help identify their source. Pilot tone bypass
will also allow you to use a transmitter that has a defec-
tive pilot tone circuit.
CAUTION: When pilot tone is bypassed and
the transmitter is turned off, excessive noise
will be present. Turn the audio level down
before bypassing pilot tone.
LECTROSONICS, INC.