Published on 10/13/2026 • Updated on 10/13/2026
A fleet integrator mounts GPS antennas on truck roofs and runs 8 m of thin coax to the telematics box in the cab. Another installer uses 1 m. Both ask the same question: does the longer cable make the position less accurate? The short answer is no, but the longer cable can stop the receiver from locking at all.
Short answer: cable length does not directly reduce GPS accuracy. A fixed cable delay of about 5 ns per meter is absorbed into the receiver clock bias. What length does change is signal strength. Too much loss lowers carrier-to-noise density (C/N0) and can cost you satellites, accuracy in poor sky view, and cold-start time.
This guide shows the loss math at the GPS L1 frequency of 1575.42 MHz and how to budget it with an active antenna.
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A signal travels through coax at about 66 to 70 percent of the speed of light, which gives roughly 4.8 to 5.1 ns of delay per meter. That is about 1.5 m of range per meter of cable.
GPS receivers solve for position and clock bias together. A constant delay affects every satellite the same way, so it appears as a clock offset and drops out of the position fix. It does matter in precision timing, where cable delay must be calibrated, and for multi-antenna or RTK systems where cables to different antennas differ.
Key idea: For a position fix, a fixed cable delay is harmless. For a one-pulse-per-second timing reference, measure or compensate the delay.
| Cable | Loss at 1.575 GHz (approx. dB/m) | Loss for 5 m | Loss for 10 m |
|---|---|---|---|
| RG174 | 1.4 | 7 dB | 14 dB |
| RG316 | 1.1 | 5.5 dB | 11 dB |
| RG58 | 0.9 | 4.5 dB | 9 dB |
| LMR-195 class | 0.65 | 3.3 dB | 6.5 dB |
| LMR-240 class | 0.5 | 2.5 dB | 5 dB |
| LMR-400 class | 0.28 | 1.4 dB | 2.8 dB |
These are typical values and rise with age, bends and cheap braid. Add 0.1 to 0.2 dB per connector.
Most GPS antennas are active: a low-noise amplifier (LNA) sits at the antenna and drives the cable. Typical LNA gain is 20 to 30 dB. The receiver datasheet states the allowed gain range at its input, often 10 to 30 dB of net gain, or a maximum cable loss figure.
Because the LNA is first, the cable loss after it adds little noise. That is why long cables work with active antennas, and why a passive antenna with a long cable performs badly: loss before the first amplifier adds directly to the noise figure.
Build the cable to the antenna spec
Tell us the antenna, receiver and length. We will build the assembly and sweep it on a VNA for loss and VSWR before shipment.
Talk to an Engineer| Situation | Recommendation |
|---|---|
| Active antenna, run under 5 m | RG174 or RG316 is fine |
| Active antenna, 5 to 15 m | Use RG58 or LMR-195 class; check receiver gain window |
| Active antenna, over 15 m | Use LMR-240 or LMR-400 class, or add an in-line amplifier |
| Passive antenna | Keep as short as possible, ideally under 1 m |
| Multi-band L1 and L5 (1176 MHz) | Loss is lower at L5, so L1 sets the limit |
DC bias for the LNA also drops with long thin cable. Check the voltage at the antenna against its minimum.
Avoid
Does coax cable length affect GPS accuracy?
Not directly. A fixed cable delay is absorbed in the receiver clock bias. Long cables only matter if loss drops signal strength too low.
How long can a GPS antenna cable be?
With an active antenna of 28 dB gain, 10 m of RG58 or 5 m of RG316 is typical. The limit is the net gain window in the receiver datasheet.
What is the delay of coax cable per meter?
About 4.8 to 5.1 ns per meter for common cables with a velocity factor of 0.66 to 0.70.
Is RG174 good enough for GPS?
For runs under about 3 m yes. Loss is about 1.4 dB/m at 1.575 GHz.
Do I need an amplifier on a long GPS cable?
Active antennas already have one. Add an in-line amplifier only when net gain is too low.
Does cable length matter for GPS timing?
Yes. Delay is about 5 ns per meter and should be compensated in precision timing and multi-antenna systems.
Length does not change the accuracy of the position solution. It changes signal strength, and signal strength changes how well the receiver locks and holds satellites. Do the loss budget and stay inside the receiver's gain window.
SigmaRF builds GPS antenna cable assemblies in India (Vadodara) and the USA (Cleveland area), VNA-swept before shipment, with lead times as short as 2 days.
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