SATCOM Link Budget Lab

SATCOM Link Budget Calculator: Learn uplink & downlink analysis, EIRP, G/T, free space path loss, C/N0, and link margin. Complete satellite communication guide.

1. TRANSMITTER & EIRP Pt + Gt - L

Transmitter Power (sync W ↔ dBW ↔ dBm)

Watts W

dBW = 10log10(W)

dBm = dBW+30

Bandwidth MHz (for density)

Tx Antenna

Diameter D (m)

Efficiency η (%)

Freq f (GHz) Uplink

λ = c/f (m)

Losses (dB)

Feed/Waveguide

Mispointing

Atmospheric (P.618)

OBO / Back-off

2. G/T (Figure of Merit) Gr -10log(Tsys)

Rx Mode

Tsys Mode

Rx Diameter (m)

Rx Efficiency (%)

Rx Freq Downlink GHz

Tant (K) - sky/antenna

LNB NF (dB)

Line Loss before LNA (dB)

3. C/No & C/N LINK C/No = EIRP - FSPL + G/T +228.6

Slant Range R (km)

Add. Path Loss (rain etc) dB

Required C/N (dB)

4. ITU-R S.524-9 UPLINK MASK Off-axis EIRP density

Off-axis angle φ (deg)

Custom density? (else auto)

ITU-R S.524-9: 2-7°: 53-25logφ, 7-9.2°: 32-25logφ (prompt variant), 9.2-48°: 8, 48-180°: -10 dBW/40kHz. Standard S.524: 2-7° 53-25logφ, 7-9.2° 32, 9.2-48° 35-25logφ, 48-180° -7.

FORMULAS & ITU REFERENCES

EIRP(dBW)=Pt(dBW)+Gt(dBi)-Lt(dB)
Pt(dBW)=10log10(P_W), Pt(dBm)=Pt(dBW)+30
Gt=10log10[η·(πD/λ)²], λ=c/f, c=299792458 m/s

G/T = Gr -10log10(Tsys) [dB/K]
Tsys=Tant+Tlna, Tlna=T0·(10^(NF/10)-1), T0=290K

C/No = EIRP - FSPL - Losses + G/T +228.6 dBHz
FSPL=20log10(4πR/λ)=92.45+20log10(f_GHz)+20log10(R_km)
C/N=C/No-10log10(BW), k=1.380649e-23, -10log(k)=228.6

ITU-R S.524-9: Max off-axis e.i.r.p. density for GSO FSS (6/14 GHz).
S.731: Cross-pol reference. S.1328-4: System characteristics. P.618: Atm/rain model.

RESULTS • LIVE CALC OK

EIRP

— dBW

— dBm | — W

Pt+Gt-Loss=EIRP

EIRP Density / 40kHz

— dBW/40kHz

EIRP / MHz

—

EIRP / 4kHz

—

EIRP / Hz

—

G/T

— dB/K

—

C/No

— dBHz

FSPL —

C/N & Margin

— dB

—

PFD at Range

— dBW/m²

S.524 MASK CHECK

—

SATCOM Link Budget Lab