User's Manual Part 1

AGC implementation

The AGC goal is to maintain stable the output power. Output power in fact can change due to the increase of

amplifier temperature. Note that when you change the operating frequency the output power change due to

the different gain at different frequency, but this change is not stabilized by this AGC algorithm. The power to

stabilize is read from external telemerasuring connector.

To keep the power stable the AGC change the power gain of VEGA.

The AGC algorithm is based on the acquisition of the optimal output power level (stored when you confirm

VEGA output power, exiting from the power level menu) and the use of 4 thresholds as below:

______action threshold

____________goal threshold

__________________optimal power value

____________goal threshold

______action threshold

The distance of thresholds from optimal value is of ±20 mV and ±30 mV measured as monitor voltage.

The AGC change output VEGA power in order to have power inside goal threshold. When this goal is

achieved the AGC stops until the power goes outside action threshold.

The AGC work is stopped immediately (output power remains blocked to that reached in the moment of the

AGC stop) when one of this condition occurs:

· One of VEGA alarms is triggered.

· AGC is chosen as external and Amplifier section triggers an alarm.

· VEGA output power too low

· AGC has change the VEGA output power too much.

In order to simplify the understanding of AGC state, this is written in the AGC menu. The possible states of

AGC are:

· Disabled: AGC disabled by local or remote menu setting.

· Idle: AGC temporary stopped (for example caused by -3dB power reduction without sync).

· Low Set: AGC stopped because external power reading too low when VEGA power has been choosed.

· Alarm: AGC stopped because Alarm signal set by Amplifier section.

· Lock: AGC has reached the desired power.

· Max/Min: AGC stopped because the correction is too hi.

· Pull Up/Down: AGC is moving Up or Down the power.

WARNING: When changing from AUTO to MANUAL power control mode, the External AGC will be disabled.