Transmitter Alignment
27
MT-3 FM Transmitter Mainboard Instruction Manual
IM20-MT3TXMN
fm audIo ProCeSSor alIGnment
Prior to commencing the standard deviation adjustment procedure, determine the specific
configuration of the transmitter (e.g., flat audio, pre-emphasis).
The following points should be noted:
• If the transmitter’s operating frequency is changed beyond the factory recommended bandwidth
or if the synthesizer is changed, the FM Audio Processor should be realigned to optimize the
transmitter’s performance. The settings tolerance is +/- 0.1 kHz.
• There are slight differences when setting up the transmitter for Flat Audio or Pre-emphasized
audio. Although the tuning procedure is the same, there will be skipped sections depending on
the transmitter type being tested.
• Although the transmitter is most commonly set up for a single frequency operation, there are
times when an application requires multiple frequencies per transmitter. This also changes the
standard tuning procedure slightly.
•
Due to the variations in the circuitry between models of synthesizer, oscillator and audio
processor, version specific tuning steps are outlined in italics.
• Section C is not an alignment procedure but is included as a final performance measurement that
confirms correct audio processor alignment.
multiple Channel transmitters
In the tuning of the FM Audio Processor for multiple channel transmitters, the procedures on the
following pages apply.
NOTE
: The maximum deviation is set on the channel, which gives the maximum deviation when
using a 1.8 kHz tone @ +10 dBm. Once that level is set (R29), it is not adjusted again.
The rest of the tuning instructions are carried out while the transmitter frequency is set for the
channel, which is roughly in the middle of the band of pre-programmed channels.
