كابل IFL للـ VSAT: الطول، الخسارة، ودليل التحديد

The cable run between your VSAT outdoor unit and your modem is called the IFL — Intermediate Frequency Link. It carries the satellite signal after the LNB has downconverted it from Ku or C-band to L-band (950–2150 MHz), and it carries the uplink signal from your BUC before transmission.

Get the IFL cable wrong — wrong type, wrong length, connectors not properly terminated — and your link budget suffers before a single packet reaches the satellite. This guide covers what the IFL is, how to choose the right cable, how to calculate loss for your specific run, and what maximum lengths apply to each cable type.

What Is an IFL Cable?

IFL stands for Intermediate Frequency Link. It is the coaxial cable connecting two points in a VSAT system:

The LNB downconverts the received satellite signal from Ku-band (10.7–12.75 GHz) or C-band (3.7–4.2 GHz) to L-band (950–2150 MHz). The BUC upconverts the transmit signal from L-band to Ku or C-band. The IFL cable carries both of these L-band signals simultaneously — receive down, transmit up — through a single coax run. The IFL also carries DC power from the modem to the LNB and, in most systems, carries the DiSEqC or tone commands that control LNB polarisation and band switching.

IFL Cable Specifications

Frequency Range

The IFL operates at L-band: 950 MHz to 2,150 MHz for most Ku-band VSAT systems.

Impedance and Connectors

All IFL cables are 50Ω. Do not use 75Ω cable (standard satellite TV cable) for IFL runs — the impedance mismatch introduces reflections and degrades signal quality. Both ends terminate in N-type connectors, the standard for VSAT IFL work. See the N-Type vs SMA vs BNC connector guide for a full comparison.

Cable Types for IFL Runs

The Times Microwave LMR series is the industry standard for VSAT IFL installations.

Attenuation at 2 GHz per 100m — visual comparison:

For a direct cable comparison, see LMR-400 vs LMR-600: Which Should You Choose?

IFL Signal Loss: How to Calculate Your Run

Attenuation accumulates with distance. Every metre of cable, every connector, and every in-line component adds insertion loss.

Total loss (dB) = Cable loss (dB/m) × Run length (m) + Connector loss × Count + In-line component losses

A good N-type connector pair adds approximately 0.1–0.2 dB. Surge arrestors add 0.3–0.5 dB each.

LMR-400 Loss Reference

LMR-600 Loss Reference

Maximum IFL Run Lengths

For runs beyond 75m on LMR-400, move to LMR-600. For runs exceeding 150m, consider relocating the modem closer to the dish or using a fibre optic IFL.

DC Power and Voltage Drop on Long Runs

The IFL cable carries DC power from the modem to the LNB (typically 13V or 18V at up to 500 mA). LMR-400 centre conductor resistance: ~1.4 Ω per 100m. At 100m with 400 mA LNB current, voltage drop ≈ 0.56V — within tolerance for most systems. At 200m+ on LMR-400, verify LNB minimum operating voltage against actual delivered voltage before commissioning.

Weatherproofing the ODU Connection

Moisture ingress at the N-type connector where the IFL meets the LNB or BUC is one of the most common causes of IFL degradation in the GCC. Weatherproof every outdoor connection on the day of installation.

Common IFL Installation Mistakes

Sourcing IFL Cable in the UAE and GCC

For professional-grade IFL installations — Times Microwave LMR-400, LMR-600, with matched N-type crimp connectors — source from a distributor carrying genuine Times Microwave product. Off-brand cable with inconsistent impedance control introduces return loss problems that are difficult to diagnose without a VNA.

Bravo Satcom carries LMR cable and RF connectors suited to VSAT IFL installations across the GCC.

Summary

The IFL cable is a critical and often underspecified component in VSAT installations. Use 50Ω LMR-series cable — LMR-400 for runs up to 75m, LMR-600 beyond that. Calculate your total IFL loss including connectors and in-line components, weatherproof every outdoor connection, and verify DC voltage delivery on long runs.