FM TRANSMITTER
TR EM 1000 HE DIG PLUS COMPACT
Technical Manual 1v2 November 2019 23
2.1.5 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.
- 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 7–7.5kHz, 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 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.
2.1.6 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.
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