LNB Cable Length Limits: What Happens When the Run Is Too Long
The Coaxial Cable Is Part of the System
It is easy to treat the coaxial cable between dish and receiver as a passive wire, but every metre of cable costs signal. If your dish is on the roof and your receiver is in a basement, the total run can easily exceed 40 metres. Once you pass the practical limit, signal drops, bit errors rise and channels start breaking up — even with a perfectly aligned dish and a new LNB.
How Much Loss Is Acceptable?
Satellite IF signals (around 1 to 2 GHz) are attenuated by cable. Typical figures for good RG6 cable are roughly 2 dB per 10 metres at 2 GHz. Cheap or old RG59 cable loses significantly more. As a rule of thumb:
- Under 30 m RG6: No problem in most installations.
- 30–60 m RG6: Usually fine if you have a strong signal and a low-noise LNB.
- Over 60 m: Consider high-grade coax, a masthead amplifier, or moving the equipment closer to the dish.
Symptoms of an Overly Long Cable Run
If the cable is too long, you may notice:
- Signal strength meter shows OK but signal quality is poor or unstable.
- HD channels pixelate while SD channels work.
- Picture worsens in rain — the weather margin is gone.
- Channels appear and disappear as you touch the cable.
How to Extend the Practical Limit
If your run is long, use low-loss quad-shield RG6 or RG11 cable. Avoid thin “satellite grade” bargain coax. Ensure every F-connector is properly compressed or screwed — a bad connector costs more dB than 10 metres of cable.
For very long runs (over 60 m), a masthead amplifier powered from the receiver can compensate. Note that not all receivers provide enough line power, and an amplifier will also amplify noise — only add one if measurements show you need it. If in doubt, have a professional check the signal levels at both ends with a satellite meter before committing to a long cable run.
