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HPA power requirements

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Ex Member
Ex Member

Oct 22nd, 2014 at 2:14pm  
Dear all,

If I have an HPA power requirements for a specific TDM/TDMA VSAT link .. Does the power requirement differ if using SCPC link with the same link specification between Hub & Remote.

can any one explain ?


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Posts: 1073
Reply #1 - Oct 22nd, 2014 at 10:51pm  
If the transmit carrier bit rate and modulation method is the same for both TDMA and SCPC then the HPA power supply rating requirements are very similar.

The difference at the HPA output is that  the TDMA carrier is intermittent whereas in the case of the SCPC version the transmission is continuous.

For TDMA the current taken from the power supply will probably vary, so the long term average power needed will be lower but the peak power when the carrier is on will be the same.  If your system uses a solar powered battery then the difference between TDMA and SCPC will be significant. You will need a lower average daily power.   You might risk providing lower cooling requirements for the TDMA option, but beware of overheating if your TDMA system is at some point called upon to make a long transmission.

Note that many, but not all, HPAs use less power when transmitting no signal or a lower power signal than the rated maximum.  Check or measure the power supply current and volts for your specific HPA model. An oscilloscope measurement at the input of the HPA may be required as the current and voltage may vary either (or both) at the TX TDMA burst rate or some 20-100kHz rate of a switch mode voltage converter inside the HPA module.

Best regards, Eric
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