TECHNICAL NOTE – OPERATION OF MT4000 TWTA
10/24/03
TN4000-3
MCL, INC.
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The number of faults counted and the window of time during which they are counted are both
adjustable by the operator (see the Adjustment Menu Screen paragraph of this document). The
window size must be greater than five times the number of faults counted in seconds.
Window Size [in seconds] = 5 x (number of faults)
4.5
HPA Gain Control
There are several ways to control the HPAs output power; these are detailed in the following
paragraphs.
4.5.1 Manual Attenuation Adjustment
Through the Gain Adjust Screen the operator can directly set the HPA output power by adjusting
the HPA gain manually. On the Computer & Remote interfaces this can be accomplished in two
ways. First, a Set Attenuator command has been provided which directly set the level of HPA
input attenuation. Second, an Increase Attenuation & Decrease Attenuation commands have been
provided. These commands adjust the attenuator from the current setting by the specified
amount. All of these methods of adjust depend on the operator watching an indication of the
HPA output power while making the adjustment.
Since the attenuator is in the input side of the HPA there is not a direct correlation between input
attenuation and output power in dBm or dBW. The difference is due to the gain compression of
the HPA. For example, a 3.0 dB change of the input attenuator will not necessarily produce a 3.0
dB change at the HPA output. However, the operator can put the HPAs RF Forward power meter
into dBm or dBW units (see the Units Select Button paragraph of this document) and manually
adjust the attenuator for the desired change in dB at the HPA output.
4.5.2 Auto Power Function
Auto Power function will regulate the RF output power within a window around the Auto Power
set level. There are several conditions that can prevent Auto Power from turning on or turn it off
when it is on.
4.5.2.1 Initializing Auto Power
The HPA front panel contains a Hold Power control and indicator that will be used to control the
Auto Power Function from the local panel. On the Computer & Remote interfaces an Auto
Power command has been provided which turns on Auto Power and sets the regulation level.
