Link budget calculator

Downlink margin for any transmitter, path and ground station. The presets reproduce the Grizu-263A budget of the review (Table 7) and the reference 1P link of the articles.

Start from

Spacecraft transmitter

FrequencyMHz

Transmit powerW

27.0 dBm

Antenna gaindBi

Line and connector lossdB

Geometry and losses

Altitudekm

Elevation°

Polarization lossdB

Atmospheric and ionospheric lossdB

Pointing and pattern allowancedB

Ground station

Antenna gaindBi

System noise temperatureK

Signal

Data ratebit/s

Modulation

Target bit error rate

Implementation lossdB

Margin at 10°+0.1 dBmargin below 3 dB

Lowest elevation, margin ≥ 0 dB10°

Lowest elevation, margin ≥ 3 dB20°

Raw data per overhead pass362 kB5.0 min with margin ≥ 3 dB

Show the data as a table

Elevation (°)	Margin
0	−3.6
5	−1.7
10	0.1
15	1.7
20	3.1
30	5.5
45	8.0
60	9.5
90	10.7

Margin over the whole elevation range for the current settings; the vertical line marks the chosen elevation.

Budget at 10° elevation
Spacecraft transmitter
Transmit power	−3.0	dBW
Line and connector loss	−0.5	dB
Antenna gain	0.0	dBi
EIRP	−3.5	dBW
Geometry and losses
Slant range	1,695	km
Free-space path loss	−149.8	dB
Polarization loss	−3.0	dB
Atmospheric and ionospheric loss	−1.0	dB
Pointing and pattern allowance	−3.0	dB
Ground station
G/T	−13.0	dB/K
Boltzmann constant	−228.6	dBW/(K·Hz)
Signal
C/N₀	55.3	dB-Hz
Data rate	39.8	dB-Hz
Eb/N₀	15.4	dB
Required Eb/N₀	13.4	dB
Implementation loss	2.0	dB
Link margin	+0.1	dB

Free-space propagation over a spherical Earth, uncoded modulation, Earth rotation neglected in the pass estimate. Real links add fading from tumbling, ionospheric scintillation and interference; keep a margin.