EXC-GT – FM super-compact transmitter series
User’s manual – Page 21 of 98
,
The MPX connector is internally connected in parallel to the RIGHT connector. As such, if the MPX connector is in
use, the simultaneous connection of signals to the LEFT and RIGHT connectors is not possible. In such case, the
highest impedance position is 5 KOhm.
7.5.a
Balanced connection to the LEFT and RIGHT connectors
The output for a mixer or any other audio processor that drives a transmitter with a balanced coaxial cable should be connected at
pin 3 (+) and pin 2 (-). The cable shield, connected to the ground of the audio driver device, must be connected to pin 1.
Balanced connection offers the greatest advantages. For example, cables connected to a source can greatly exceed 100
meters in length.
7.5.b
Unbalanced connection to the LEFT and RIGHT connectors
For driving with an unbalanced signal, input pin 2 must be short-circuited with the ground and the shield to pin 1, while the signal
must go to pin 3. In such case, the highest impedance selection will be 5 KOhm rather than 10 KOhm.
7.6
Connection to the MPX input
Connect an externally created multiplex signal to the MPX input using a suitable encoder.
If the length of the cable delivering the signal to the MPX connector is only a few meters long, a 50 Ohm (RG58) cable can be
used. If the distance is greater, a 75 Ohm (RG59) or 92 Ohm (RG62) cable should be used.
7.6.a Checking
the
pilot tone
in stereophonic transmission
Where the internal stereo encoder is used, the level of the stereo driver tone, which is usually set internally at 9-10% of the
modulation (from -21 to -20dB) corresponding to the standard established deviation of 7 – 7.5 kHz, cannot be changed externally.
Where the stereo modulation signal is externally generated by a separate stereo encoder, the driver tone must be measured in the
absence of audio modulation and all other auxiliary signals, as described below:
1)
Disconnect all signals from the external stereo encoder input, and any RDS or SCA signals.
2) Select
the
VIEW
-
AUX
menu (section 10.2.c) and confirm that the driver tone is now the only available signal. The standard
level is as indicated above, 9-10% (-21 to -20dB), and can be consequently adjusted on the external stereo encoder as
required.
3)
Reconnect the previously disconnected signals.
7.7
Changing the input impedance
As previously explained, the input impedance on the modulation inputs can be changed. Selection of the input impedance is one of
the very few settings that can only be changed internally, as follows:
1)
Disconnect the mains.
2)
Unscrew the screws that hold the top cover in place (16 or more cross-head screws will require removal, depending on the
model).
3)
Remove the top cover and store it in a safe place.
4)
Identify the input card.
