Published on 10/13/2026 • Updated on 10/13/2026
A product designer hides a 2.4 GHz antenna inside a metal enclosure, then adds a 2 m extension cable to put it outside. The link range goes up, even though cable loss is now 3 dB. That sounds wrong. It is not, and it is the one case where a longer cable is better.
Short answer: a longer antenna cable is almost never better, because every meter of coax costs signal. The exception is when the longer cable lets you put the antenna in a better place, where the gain from placement is bigger than the cable loss.
Here is the math, the exceptions and a decision rule.
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Coax loss in dB is proportional to length. At 2.4 GHz RG316 loses about 1.4 dB/m, RG58 about 1.1 dB/m and LMR-195 class about 0.8 dB/m. Every 3 dB lost halves the power going to or from the antenna.
| Extension | RG316 at 2.4 GHz | RG316 at 5.8 GHz | LMR-195 at 5.8 GHz |
|---|---|---|---|
| 0.5 m | 0.7 dB | 1.1 dB | 0.7 dB |
| 1 m | 1.4 dB | 2.2 dB | 1.3 dB |
| 2 m | 2.8 dB | 4.4 dB | 2.6 dB |
| 5 m | 7 dB | 11 dB | 6.5 dB |
Loss applies on transmit and receive, so the link takes it twice. A 3 dB cable loss on both ends of a link costs 6 dB of margin.
Placement beats loss
Get the right length, not the longest
Tell us the frequency and the distance. We will build the assembly and sweep it on a VNA for VSWR and insertion loss before shipment.
Talk to an EngineerIf you need a long cable, put an amplifier at the antenna end. A low-noise amplifier before the cable sets the system noise figure, so the cable loss that follows matters much less. This is how active GPS antennas and TV antennas work. For a transmitter, a power amplifier at the antenna works the same way, but needs DC power and a bias tee. See our antenna cable loss vs amplifier gain guide on this blog.
| Link type | Longer cable acceptable? |
|---|---|
| Receive-only with LNA at antenna | Yes |
| Receive-only, passive antenna | No |
| Transmit, no amplifier | No |
| Wi-Fi or cellular, 5 GHz and above | Almost never |
| Issue | Detail |
|---|---|
| Cable on the antenna ground plane | Common-mode current on the shield can detune a small antenna; a ferrite choke helps |
| Resonant length | Shield lengths near a quarter wavelength can resonate with the antenna |
| VSWR reading | Measured at the radio, long loss cable hides a bad antenna |
| Phase and timing | Delay is about 5 ns per meter |
Avoid
Is a longer antenna cable ever better?
Only when it lets you move the antenna to a clearly better location. Otherwise every extra meter adds loss.
How much signal do I lose with an antenna extension cable?
At 2.4 GHz RG316 loses about 1.4 dB per meter and RG58 about 1.1 dB. At 5.8 GHz the loss is about 2.2 dB per meter for RG316.
Does cable length affect Wi-Fi range?
Yes. Loss applies on transmit and receive, so 3 dB of cable loss costs about 6 dB of link margin.
Can I use a longer cable and add an amplifier?
Yes for receive. Place a low-noise amplifier at the antenna end so the cable loss comes after it.
What is the best cable for a long antenna run?
A low-loss cable such as LMR-240 or LMR-400 class, with as few connectors as possible.
Should I coil excess antenna cable?
No. Cut it to length. A coil adds loss and can radiate or pick up noise.
Cut antenna cable to the shortest practical length. Make an exception only when you can show that placement gains more than the loss, and use low-loss cable with an LNA when the run is long.
SigmaRF builds antenna cable assemblies to exact length in India (Vadodara) and the USA (Cleveland area), VNA-swept before shipment, with lead times as short as 2 days.
Order antenna cable to length
Send the frequency, length and connectors.
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