IFL Cable for VSAT: Length, Loss, and Sizing Guide

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:

🛰️ ODU
BUC + LNB

IFL Cable
L-band 950–2150 MHz
+ DC power + DiSEqC

📡 IDU
VSAT Modem

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.

System Type	IFL Frequency Range
Ku-band VSAT (standard)	950–1,450 MHz (low band) or 950–2,150 MHz (wideband)
Ku-band VSAT (wideband LNB)	950–2,150 MHz
Ka-band VSAT	950–2,150 MHz
C-band VSAT	950–1,750 MHz (typical)

Always check your modem and LNB specs. The IFL cable must have low attenuation across the full operating frequency range of your specific system.

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.

Cable	OD	Loss at 1 GHz	Loss at 2 GHz	DC Resistance (Ω/100m)	Typical Use
LMR-240	7.3 mm	10.2 dB/100m	14.8 dB/100m	3.0	Short jumpers, tight spaces
LMR-400	10.8 mm	5.6 dB/100m	8.0 dB/100m	1.4	Standard IFL runs up to 75m
LMR-600	15.8 mm	3.6 dB/100m	5.2 dB/100m	0.9	Long runs 75–130m
LMR-900	22.9 mm	2.4 dB/100m	3.5 dB/100m	0.6	Very long runs 130m+

Attenuation at 2 GHz per 100m — visual comparison:

LMR-240

14.8 dB

LMR-400

8.0 dB

LMR-600

5.2 dB

LMR-900

3.5 dB

⚠️ Do not use RG6 for VSAT IFL. RG6 is 75Ω — not 50Ω. Impedance mismatch affects every interface. Higher attenuation at L-band, lower DC current capacity, less shielding. It is a domestic TV cable and does not belong in a professional VSAT installation.

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

Run Length	Loss at 1 GHz	Loss at 1.5 GHz	Loss at 2 GHz
10 m	0.56 dB	0.69 dB	0.80 dB
20 m	1.12 dB	1.38 dB	1.60 dB
30 m	1.68 dB	2.07 dB	2.40 dB
40 m	2.24 dB	2.76 dB	3.20 dB
50 m	2.80 dB	3.45 dB	4.00 dB
60 m	3.36 dB	4.14 dB	4.80 dB
75 m	4.20 dB	5.18 dB	6.00 dB
100 m	5.60 dB	6.90 dB	8.00 dB

LMR-600 Loss Reference

Run Length	Loss at 1 GHz	Loss at 1.5 GHz	Loss at 2 GHz
30 m	1.08 dB	1.33 dB	1.56 dB
50 m	1.80 dB	2.22 dB	2.60 dB
75 m	2.70 dB	3.33 dB	3.90 dB
100 m	3.60 dB	4.44 dB	5.20 dB
150 m	5.40 dB	6.66 dB	7.80 dB

✅ Worked example 60m LMR-400, wideband Ku-band (to 2 GHz), 4 N-type connectors, 1 surge arrestor:

Cable loss at 2 GHz: 4.80 dB
Connectors (4 × 0.15 dB): 0.60 dB
Surge arrestor: 0.40 dB
Total IFL loss: 5.80 dB

Maximum IFL Run Lengths

Cable Type	Practical Maximum	Notes
LMR-240	25–30 m	Short jumpers only
LMR-400	50–75 m	Standard for most commercial sites
LMR-600	100–130 m	Longer buildings, rooftop-to-basement
LMR-900	150–200 m	Large campus or remote antenna

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.

Terminate with an N-type crimp connector — see the LMR connector crimping guide for strip dimensions and tooling.
Mate the connector — N-type hex nut finger-tight plus a quarter turn with a 7/16″ spanner.
Wrap with self-amalgamating tape, starting below the connector body, 50% overlap, two full passes minimum.
Overwrap with PVC electrical tape for UV protection.
Secure the cable to the mount at regular intervals to prevent wind stress on the connector.

⚠️ Never use PVC tape alone. It lifts in heat, traps moisture, and degrades in direct sunlight. Self-amalgamating tape fuses into a waterproof seal — use it first, PVC over the top.

Common IFL Installation Mistakes

Mistake	Effect	Fix
Using 75Ω RG6 cable	Impedance mismatch, high attenuation, poor transmit performance	Use 50Ω LMR-series cable
Exceeding minimum bend radius	Kinked dielectric, local attenuation increase	Route through gentle curves; use conduit elbows
Unterminated cable ends during installation	Moisture ingress into dielectric	Cap unused ends with N-type terminator immediately
Outdoor connections not weatherproofed	Connector corrosion, rising insertion loss	Self-amalgamating tape every outdoor connection, same day
IFL run parallel to AC mains	RF interference pickup at L-band	Separate by 100mm minimum; use metal conduit

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.