T.E.M. A07B500S Manual - page 24
A07B500S manual
Pag. 24
All the rules concerning the radio transmitters in FM band include some limits of accuracy and
stability of the output frequency. These limits usually depend on parameters of internal crystal
reference, which are at the same time connected firstly to the temperature and ageing of the crystal
itself. For this reason the crystal have high performance and guarantees a considerable thermal
stability, however a frequency correction due to ageing is easily implemented just manually.
The present screen shot allows a very fine adjustment of the frequency value assigned to the radio
station without the need to open the transmitter. By entering a correction factor between 0 and 255,
the transmitter frequency can be corrected with a 20Hz step only; this operation can be performed
during the normal periodical check of the transmitter or, as it is shown below, through a remote
telecontrol ( modem , GSM ).
By entering the new correction value, it’s possible to reach a 2KHz offset in comparison to the
central value.
4.6.12
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In this case it’s possible to insert the pre-emphasis or to set the transmitter from mono to stereo and
vice versa.
The pre-emphasis value (50 or 75µs) is switched by a jumper placed on the rear window of the rack.
The pre-emphasis operates on the LEFT and RIGHT channels only.
By choosing the STEREO option, the LEFT and RIGHT channels are encoded with the stereo
subcarrier addition, from which it’s possible to get a synchronism in the IN/OUT rear connector
(1Vpp sine wave).