User Manual
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conditions. They are:
- MPEG-TS synchronization missing;
- uncorrected input packet (only in 204 RS coded mode with ASI input mode);
- bit rate underflow/overflow (only if bit rate adaptation is performed).
The above conditions trigger an alarm only for the input which is currently used by the ATSC TRANSMITTER.
1.4.10 AGC: IMPLEMENTATION AND DETAILS
The use of external AGC helps the ATSC TRANSMITTER to maintain stable the output power of a high-
power transmitter. With a menu setting (see the Menu Management paragraph) you can choose among
stabilizing the output power of the exciter (external AGC disabled) or stabilizing the output power of a high-
power transmitter (external AGC enabled). In this case a proper cabling between the ATSC TRANSMITTER
and the high-power amplifier stage is necessary. The cable (AGC cable) shall be connected to the TLM port
of the ATSC TRANSMITTER on one side. In the following table the three signals and pins used in the TLM
port are listed. The pinout connection of the cable depends on the specific amplifier used. Refer to your
amplifier user's manual to find the port and pins of the corresponding signal.
PIN I/O DESCRIPTION
4 I Forward Power (0-5V)
5-GND
8 I Alarm (GND=Alarm / Open=Normal)
The AGC goal is to maintain the output power stable. Output power in fact can change due to the increase of
the amplifier temperature. Note that when you change the operating frequency the output power changes due
to the different gain at different frequency, but this change is not stabilized by the AGC algorithm. The transmitter
power to be stabilized is read from TLM port.
To keep the power stable, the AGC changes the power gain of the ATSC TRANSMITTER.
The AGC algorithm is based on the acquisition of the optimal output power level, stored when you confirm the
output power level in the Power menu (see the Menu management paragraph) and the use of 4 thresholds
as below:
____action threshold
________goal threshold
___________optimal power value
________goal threshold
____action threshold