Link Budget calculations.

Path Loss Formula   L(dB) =32.45 +20 log F(MHz) +20 log D(Km)

 

maximum distance for 800 Km polar orbit                   3000 Kms 

minimum distance for orbit                                          800 Kms

 

Downlink:

Maximum path loss at 29 MHz                                    = 131.24 dB

Maximum path loss at 146 MHz                                  = 145.28 dB

Maximum path loss at 435 MHz                                  = 154.73 dB

Maximum path loss at 2400 MHz                                = 169.59 dB

 

Assume spacecraft antenna gain of 0 dBi, 1 watt transmitter power,

and the following net antenna gains for the ground station:

29 MHz                                                                        = 0 dBi

146 MHz                                                                      = 6 dBi

435 MHz                                                                      = 9 dBi

2400 MHz                                                                    = 15 dBi

 

we obtain the received signals at maximum range as follows:

29 MHz                                                                        = -101.24 dBm

146 MHz                                                                      = -109.28 dBm

435 MHz                                                                      = -115.73 dBm

2400 MHz                                                                    = -124.59 dBm

 

So 29 MHz, 146 MHz, or 435 MHz will provide a workable downlink signal.

 

Doppler shift:

Taken from "The Satellite Experimenters Handbook"  table 13-1 page 13-5.

29 MHz                                                                        = 0.70 KHz

146 MHz                                                                      = 3.45 KHz

435 MHz                                                                      = 10.3 KHz

2400 MHz                                                                    = 56.7 KHz

So 29 MHz, 146 MHz, or 435 MHz will provide a workable downlink signal.

 

Uplink:

Maximum path loss at 146 MHz                                  = 145.28 dB

Maximum path loss at 435 MHz                                  = 154.73 dB

Maximum path loss at 1270 MHz                                = 164.06 dB

 

Assume spacecraft antenna gain of 0 dBi, 10 watts transmitter power,

and the following net antenna gains for the ground station:

146 MHz                                                                      = 6 dBi

435 MHz                                                                      = 9 dBi

1270 MHz                                                                    = 15 dBi

 

we obtain at the satellite at maximum range received signals as follows:

146 MHz                                                                      = -99.28 dBm

435 MHz                                                                      = -105.73 dBm

1270 MHz                                                                    = -109.06 dBm

 

So 146 MHz, 435 MHz or 1270 MHz will provide a workable uplink signal.

 

Doppler shift:

146 MHz                                                                       = 3.45 KHz

435 MHz                                                                       = 10.3 KHz

1270 MHz                                                                      = 30.1 KHz

So 146 MHz or 435 MHz will provide a workable uplink signal.

1270 MHz will work but will require special doppler compensation.

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Last updated 22/07/2002