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.

If you’re specifying cable for a VSAT antenna, two-way radio system, or any RF installation, you’ve likely hit the same question: LMR-400 or LMR-600? Both are Times Microwave Systems’ most popular flexible coax cables — low loss, UV-resistant, and built for outdoor use. The difference comes down to run length, signal loss budget, and how much space you have to work with.

This guide gives you the specs, the attenuation data, and a clear decision rule.

Physical Specs: Side by Side

The bigger conductor in LMR-600 (0.176″ vs 0.108″) is the reason it outperforms LMR-400 on signal loss — lower DC resistance means less energy dissipated as heat per foot of cable.

Signal Attenuation: The Numbers That Matter

Attenuation is measured in dB per 100 feet — the lower the number, the better. Based on Times Microwave Systems official specifications:

LMR-600 delivers roughly 35% less attenuation at all frequencies compared to LMR-400. That gap compounds quickly over longer runs.

When LMR-400 Is the Right Choice

LMR-400 is the industry standard for good reason. Choose it when:

Run length is under 30 metres (100 ft). At this distance, the loss difference between LMR-400 and LMR-600 is minimal and doesn’t justify the cost or weight difference.

You need flexibility. With a 1.0″ minimum bend radius, LMR-400 is significantly easier to route through conduit, around corners, and in tight equipment racks.

Weight matters. At 0.068 lbs/ft (vs 0.131 lbs/ft for LMR-600), LMR-400 is nearly half the weight — important for rooftop or tower installations where cable tray loading is a concern.

Budget is a factor. LMR-400 is meaningfully less expensive per metre than LMR-600, making it the practical default for short-to-medium runs.

LMR-400 is the cable of choice for most VSAT antenna-to-modem runs, two-way radio base station feeders, and short rooftop drops.

When You Should Upgrade to LMR-600

Move to LMR-600 when signal loss budget is tight:

Run length exceeds 30–40 metres (100–130 ft). Beyond this point, the accumulated loss in LMR-400 starts eating into your link margin — especially at higher frequencies (Ku-band IF at 950–1,450 MHz and above).

High-power applications. LMR-600’s larger conductor handles more RF power before thermal losses become a concern — relevant for high-wattage BUC installations where every dB matters.

You’re running at 1 GHz or above over long distances. Attenuation increases with frequency. A 60-metre Ku-band IF run at 1,500 MHz in LMR-400 loses ~7.0 dB. In LMR-600, the same run loses ~4.4 dB. That 2.6 dB difference can be the margin between a stable link and intermittent dropouts.

Maximum cable run distances: LMR-600 supports antenna cable runs up to 400 ft (120 m) without inline amplification. LMR-400 is typically limited to around 200 ft (60 m) before loss becomes unacceptable at Ku-band frequencies.

Cost and Installation

LMR-600 typically costs 30–50% more per metre than LMR-400. It’s also heavier and stiffer, requiring more careful routing and stronger support hardware — cable trays and support clamps need to account for the increased weight (0.131 lbs/ft vs 0.068 lbs/ft).

Connectors are cable-specific — don’t mix LMR-400 and LMR-600 connectors. If you’re terminating in the field, LMR-600 requires a larger stripper tool and more robust crimp or compression fittings. Both cables accept Times Microwave Systems EZ push-on connectors, which eliminates soldering on site.

The Simple Decision Rule

If you’re ever in doubt, calculate your total path loss budget: add up the cable loss, connector insertion loss (~0.1 dB per connector), and any other passive components. If the total pushes you within 1–2 dB of your link margin, upgrade to LMR-600.

Frequently Asked Questions

Can I mix LMR-400 and LMR-600 in the same run?

Yes, but only with proper barrel adapters. Keep the LMR-600 section on the longer runs and use LMR-400 for short flexible jumpers at each end.

Are LMR-400 and LMR-600 connectors interchangeable?

No. Each cable requires its own connector size. LMR-400 and LMR-600 both accept N-type, TNC, and SMA connectors — but in their respective sizes. They are not physically compatible with each other.

Which cable is better for outdoor VSAT installations in hot climates?

Both use a black UV-protected polyethylene jacket rated for −40°C to +85°C, making them suitable for the UAE and GCC climate. For buried runs, specify LMR-DB (watertight/flooded version) from Times Microwave Systems.

Does LMR-600 need different support hardware?

Yes. At 0.131 lbs/ft, LMR-600 requires stronger cable trays and more frequent support points — approximately every 18–24 inches on horizontal runs vs every 24–36 inches for LMR-400.

Shop LMR Coaxial Cable at Bravo Satcom