Multi Channel Transmitter (MCTX) - Installation,
Commissioning and Maintenance
Page 13 of 16
The audio signal is noisy
All the audio signals are noisy
and reception is poor
There are areas of poor reception
and d ead sp ots
The received signal is in mono
The signal fades as p eople w alk
round the room
T h e
t r a n s m i t t e r c a u s e s
interference on an adjacent TV or
radio.
No audio signal
The received signal has a low
frequency hum
The volume on one channel of
the receiver is low
The receiver is too far from the transmitter. The aerial has been mounted in a
poor location or is horizontal instead of vertical. Th ere are ob jects in the signal
path. You may consider transmitting in mono which will improve the signal
to noise ratio.
The upconverter may be overloaded, check the output of the transmitter using
the test aerial and a spectrum analyser (see output dis pla ys sho wn abov e). Is
there an attenu ator in the VHF feed to the upconverter? Is it the correct value?
There are reflections on the room which are causing phase cancelling in some
areas. Either re-site the transmitter aerial or re-site the receivers.
The transm itter is shipped with all the channels in mono because many of the
audio sources are in mono. A mono signal will have a better signal to noise
ratio and provid es coverage over a greater distance compared to a stereo
system.
Check the signal strength with th e test aerial an d spe ctrum a nalyser. If it is
poor check the outpu t of the up conv erter wh ich sho uld be 0dBM (remember
to use a 20 dB attenuator at this point to protect the analyser). If it is correct
then increase the height of the transm itter aerial or re-site it. Low ceilings may
also cause this problem.
The transmitter may be too close to the TV or radio receiver. If the TV
installation is poor or the received TV signal is weak. Some TV distribution
systems use passive splitters which reduce the signal into the TV set. The TV
distribution cable may have a poor screen or earth connection. The TV
distribution amplifiers or splitters do not have sufficient immunity to RF
signals.
Check the in put b argrap hs for a sign al. Is the input volume control set too
low? Are the input signal leads connected? Is the audio source switched on?
Check for hum loops (multiple earths) on the installation .
Check the input channel volume control
User maintenance
The venue staff should be instructed on how to operate the transmitter. The only user controls
are the channel volume controls which can be adjusted to accommodate different input signals.
You should emphasise that there are no user controls inside the units which have been set up for
their optimum performance. Should they interfere with the transmitter it will no longer comply
with the standard for wireless audio and the warranty will be void.
