WIRELESS SYSTEMS
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2.
INSTRUCTIONS FOR INSTALLATION
Read the instructions concerning the installation and operation of this
equipment carefully before using it. In order to ensure correct operation
of the equipment it is necessary to guarantee good reception, for
example by not enclosing the receiver inside a cabinet, particularly not
one made of metal. Also make sure that the equipment is kept away
from sources of heat. Make sure that all the inputs and outputs are
correctly connected to the equipment before switching it on. The
equipment is supplied with an external power supply unit and voltage
divider, to be connected to the 230 V 50 Hz mains supply. Avoid the risk
of electric shocks or damage that could be caused by introducing
objects, particularly those made of metal, inside the power supply unit.
If any liquid should be spilt accidentally onto the equipment or power
supply unit, unplug them immediately from the mains and contact the
nearest PASO Assistance Centre.
3.
CONNECTIONS
Connect one of the two outputs [8] or [9] of the receiver to one of the
inputs of the sound-broadcasting system. The connection may be
either of the unbalanced [8] or of the balanced type [9]. Keeping the
different levels of the output signals in mind, we suggest using output
[8] for connections to power units or to the auxiliary inputs of mixers or
amplifiers, and output [9] for auxiliary inputs or the balanced microphone
inputs of mixers or amplifiers. The “AUX” output [8] also has a level
control “AUX VOL.” [7]. Figure 3.1 shows the connections of the
sockets. Use the power supply unit supplied with the equipment to
connect it to the mains. Connect the 12 V plug to the socket [5] in the
R208-T and then plug the transformer into a 230 V 50 Hz mains outlet.
4.
PRINCIPLE OF OPERATION OF THE RECEIVER
The radio-frequency signal detected by an aerial may be weakened
due to its being reflected and absorbed by walls, ceilings and so on,
particularly if they are made of metal, so much so that the squelch
circuit trips and mutes the audio-frequency output signal. This
weakening effect can be avoided to a great extent by using two
separate aerials, each with its own receiving circuits. A special technique
for comparing the two signals received enables the one with the best
signal/noise ratio to be determined in real time, and this is then sent to
the input of the demodulation circuits.
5. SQUELCH CIRCUIT AND PILOT TONE
This wireless microphone system uses a technologically advanced
circuit for squelching the receiver. The operation of this circuit is based
on the detection and identification of a specific signal, the so-called
“pilot tone”, sent by its own transmitter together with the carrier
frequency. The squelch circuit therefore only activates the receiver if
the level of the signal received by both aerials is higher than the
threshold level that has been set, and only if the pilot tone is detected.
This prevents rustling and other background noise generated by
unwanted signals picked up by the aerials from reaching the
broadcasting system. The sensitivity of the squelch circuit can be
adjusted by means of the potentiometer [6].
Specifically, by turning the squelch control completely in a clockwise
direction, the maximum sensitivity of the receiver is achieved (exclusion
of muting).
6.
USE OF THE RECEIVER
Make the connections for the receiver as indicated under point 3.
Make sure that the frequencies of the receiver and of the transmitter
coincide. Extend the two telescopic aerials of the receiver [1] to their
maximum length and position them in such a way that they form an
angle of about 90° to one another. Increase sensitivity to the maximum
level by turning the squelch control [6] completely in a clockwise
direction and turn on the equipment by means of the switch [4]. The
“MUTE” [2] signalling lamp will light up to indicate that the squelch
circuit is working and that the receiver is on. Switch on the transmitter
and check, at the same time, that the “MUTE” signalling lamp [2]
extinguishes. Adjust the sensitivity of the receiver by means of the
squelch threshold control (potentiometer [6]), as little as possible so
as to suppress any noise (rustling or croaking) that might occur when
the system reaches the limit of its working range. The “ANT1” and
“ANT2” signalling lamps [3] will indicate in real time which of the two
aerials is detecting the strongest signal. Then adjust the volume control
of the mixer or amplifier to which the receiver is connected so as to
achieve the desired listening level.
7.
TIPS
Following are a few tips so that you will be able to use the wireless
microphone system to your full satisfaction:
7.1 Always keep the efficiency of the battery inside the transmitter
under control.
7.2 Always keep the squelch level of the receiver as low as possible,
compatibly with the operating conditions (operating range,
obstacles, charge of the transmitter battery).
7.3 Carry out a trial with the transmitter in the area concerned, in
order to check whether there are any skip areas. If necessary,
identify the best direction for the aerials and reposition the receiver
in a place that provides better reception.
7.4 During the inspection referred to under point 7.3, also check
whether there is any acoustic feedback (Larsen effect). If there
is, we recommend using one or more of the following methods in
order to eliminate it:
-
positioning the loudspeakers so that they point in a different
direction;
-
increasing the distance between the area where the transmitter
is being used and the closest loudspeakers;
-
lowering the transmitter sensitivity (if this control is provided)
-
lowering the volume level of the broadcasting system.
8.
TECHNICAL SPECIFICATIONS
Carrier frequency
160÷245 MHz (VHF)
Pilot tone
32,768 kHz
Modulation type
FM (F3E)
RF Sensibility
3 µV
Frequency stability
± 0,005% / 25°C
Rated deviation
± 40 kHz at 1 sinusoidal kHz
Audio-frequency response
50÷15000 Hz
Harmonic distorsion
< 1% at rated deviation
S/N ratio
> 90 dB
Audio outputs
MICRO 60 mV
AUX 0÷2 V
Power supply
12÷18 Vcc
Power consumption
< 300 mA
Size (L x H x D)
222 x 40 x 118 mm
Weight
550 g
Fig. 3.1
AUX unbalanced output
1
shield
2
not connected
3
signal
MICRO balanced output
1
shield
2
signal (hot side)
3
signal (cold side)
11-504.p65
23/11/99, 14:31
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