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Satellite Power Signal Budget Planner

The Satellite Power Signal Budget Planner estimates received signal level and link margin for a telemetry or control link associated with a satellite power subsystem or its mission operations. It combines transmitter power, antenna gains, propagation loss, miscellaneous losses, and receiver sensitivity in one dB-based budget.

The planner is useful for preliminary communications checks, especially when power-system telemetry must remain available across a planned range. The final link margin shows how far the estimated received level sits above or below the selected receiver threshold.

Calculator inputs

dBW
dBi
dBi
dB
dB
dBW
Result
—
Estimated link margin
Received power—
Transmit EIRP—
Receiver sensitivity—

1. Enter transmitter power
Use power at the transmitter output in dBW.

2. Add antenna gains
Enter transmit and receive antenna gains in dBi.

3. Enter propagation loss
Use the path-loss estimate for the intended frequency and range.

4. Include other losses
Combine pointing, polarization, cable, atmospheric, or implementation losses that are not already included.

5. Set receiver sensitivity
Enter the minimum received power required by the selected receiver or demodulation criterion.

6. Check link margin
A positive margin means the estimated received level is above the entered threshold.

Received power (dBW) = transmit power + Tx gain + Rx gain − path loss − other losses
Link margin (dB) = received power − receiver sensitivity
EIRP (dBW) = transmit power + Tx gain

All terms must use compatible logarithmic units. This planner treats losses as positive dB quantities that are subtracted. A complete communications design may also include noise temperature, bandwidth, data rate, coding gain, required Eb/N0, and statistical fading.

What the result means

The link margin is the difference between estimated received power and the receiver sensitivity entered for the scenario.

Positive margin is not a guarantee of availability; real links need appropriate contingency for fading, pointing error, hardware variation, and mission risk.

Given

  • Transmit power = 10 dBW
  • Tx gain = 3 dBi
  • Rx gain = 12 dBi
  • Path loss = 155 dB
  • Other losses = 3 dB
  • Receiver sensitivity = −135 dBW

Calculation
Received power = 10 + 3 + 12 − 155 − 3 = −133 dBW. Link margin = −133 − (−135) = 2 dB.

Result
Link margin = 2 dB.

The modeled link is 2 dB above the chosen receiver threshold, before any unmodeled contingencies.

What does a negative link margin mean?

The estimated received signal is below the sensitivity threshold by the magnitude of the negative margin. That usually indicates the link budget needs more gain, more transmit power, lower loss, or a more sensitive receiver.

Can I enter transmitter power in watts?

Convert watts to dBW before using this planner: dBW = 10 × log10(watts). The calculator itself expects a logarithmic power value.

Should atmospheric loss be included in path loss or other losses?

Either approach can work if it is counted once. Keep free-space loss and additional propagation or implementation losses separated if you want the budget to remain easy to audit.

Is receiver sensitivity the same as required Eb/N0?

No. Sensitivity is an input power threshold, while Eb/N0 is an energy-per-bit to noise-density requirement. A fuller digital-link budget connects those through data rate, bandwidth, and receiver noise.

Why can satellite power affect a signal budget?

Available electrical power can limit transmitter output and duty cycle. This planner isolates the RF link arithmetic so those power-system constraints can be tested through the transmit-power input.