The Truth About Antenna Cable Loss, How Coax Affects Signal Strength More Than You Think
Posted by Gordon Reed on 3rd Dec 2025
Why Cable Loss Matters More Than Most People Realize:
Every RF system, whether it is a simple mobile hotspot or a multi-antenna 5G enterprise router, depends on the integrity of its signal path. Antennas get most of the attention, but the coaxial cable that connects your device to that antenna is equally important. Even a few decibels of loss in the cable can dramatically alter received signal levels, degrade SINR, and reduce throughput. In higher frequency bands, such as 5G NR n77 or Wi-Fi 6/7, the effects of cable loss become even more severe. Understanding how coax behaves is essential for building a reliable RF link, and in many cases, it determines whether a system performs well or struggles.
Understanding Cable Loss, What It Is and Why It Happens:
Coaxial cable is not a perfect conductor, and attenuation occurs due to multiple physical mechanisms. Resistive losses result from conductor resistance and the skin effect, which forces RF current toward the conductor’s outer surface at higher frequencies. Dielectric losses occur as the insulating material absorbs a portion of the electromagnetic field, converting it to heat. The shielding structure introduces additional losses, especially if the braid density or foil quality is insufficient. All of these mechanisms compound and increase as frequency rises. The result is measurable insertion loss, and it directly reduces the effective power that reaches the antenna or returns to the radio.
Distance and Frequency, The Two Dominant Drivers of Attenuation:
Cable loss increases with length, but frequency has an exponential influence on attenuation. A cable that performs reasonably well at 700 MHz may introduce unacceptable loss at 2.4 GHz or 3.5 GHz. By the time a signal reaches 5 to 6 GHz, even high-quality coax loses several decibels over modest distances.
For example, a 20 foot run of a mid-grade cable may lose around:
- ~1 dB at 700 MHz
- ~2.5 dB at 2.4 GHz
- ~3.5 to 4.5 dB at 3.5 GHz (CBRS and many 5G bands)
- ~5 to 6 dB at 5.8 GHz
These numbers illustrate why 5G, Wi-Fi 6, and tri-band Wi-Fi systems require careful cable selection and minimal length. Frequency and distance work together, and both must be considered in any installation.
The Role of Cable Construction, Why Some Cables Perform Better Than Others:
Cable loss is heavily influenced by how the coax is built. Solid copper center conductors offer lower resistance compared to copper-clad steel, providing better performance at high frequencies. The dielectric material, whether foamed polyethylene or a lower-grade solid dielectric, also plays a major role in attenuation. Shielding matters too, and cables with a bonded foil plus a high-coverage braid maintain lower loss and better shielding effectiveness against external interference.
Small, flexible cables are easier to route, but they inherently have more attenuation. Larger diameter cables such as AGA240 or AGA400 reduce loss and improve system performance, especially in cellular and high-bandwidth Wi-Fi deployments where every decibel counts.
Connectors, The Often Overlooked Source of Additional Loss and Mismatch:
Connectors are part of the RF chain and introduce their own insertion loss, typically a small fraction of a decibel. However, poor connector design, incorrect plating, improper pin depth, or off-spec impedance can cause reflection due to mismatch. This raises VSWR and becomes more problematic as frequency increases.
The connector interface attached to the router or gateway is equally important. SMA connectors offer excellent performance when properly installed, while TS9 and u.FL require much more care due to their small mechanical footprint. When using larger antennas or longer cable runs, connectors such as N-type and TNC often deliver better loss characteristics and durability. The entire chain must be impedance-matched and assembled with precision to avoid performance degradation.
Return Loss, VSWR, and Reflections Introduced by Poor Coax:
Low-quality or damaged coaxial cable can cause reflections, which show up as return loss and elevated VSWR. These reflections reduce the power delivered to the antenna, and they also limit the power returning from the antenna to the radio’s receiver. In cellular systems, high VSWR can force the modem to reduce its transmit power to protect its power amplifier, which directly reduces uplink performance.
Reflections compound with cable loss, meaning insertion loss plus mismatch loss can degrade the link well beyond the expected attenuation figures. These effects are especially noticeable in high-frequency bands where tight impedance control is critical.
How a “Small” Loss Adds Up Quickly:
Consider a scenario with the following components:
- A router or hotspot
- A 20 foot length of AGA240 class cable
- An outdoor 2x2 MIMO cellular antenna
If the loss is 2.4 dB per line at 2.4 GHz, the antenna effectively receives less than sixty percent of the conducted radio power. At 3.5 GHz, that loss may be closer to 3.5 dB, meaning only about forty-five percent of the power reaches the antenna. On the return path, the received signal is attenuated again. The cumulative effect is a noticeable drop in RSRP and measurable degradation in SINR, which are two critical metrics that cellular modems rely on for carrier aggregation, modulation order, and handoff decisions.
This is the point where users observe the system dropping from 5G to LTE or losing the ability to maintain higher throughput levels. The cable is often the limiting factor, not the antenna or the radio.
Why Shorter Is Always Better, When Possible:
The most effective way to reduce cable loss is to reduce cable length. Moving the router closer to the antenna or installing equipment in a location with stronger native signal drastically improves performance. Direct-to-device antennas, such as paddle antennas or low-loss MIMO whips, can outperform long coaxial runs even when the remote antenna has higher gain.
When long runs cannot be avoided, selecting a higher-grade cable becomes essential, especially in high-frequency applications where loss accumulates rapidly.
How to Choose the Right Coax for Your Deployment:
AntennaGear provides multiple cable classes designed to minimize attenuation while offering flexibility and durability.
- AGA195 Cable
Ideal for short runs, low-band LTE, IoT, and compact installations where flexibility matters more than absolute loss. - AGA240 Cable
A strong middle-ground for most cellular and Wi-Fi deployments. Suitable for moderate runs at mid and high frequencies. - AGA400 Cable
Designed for long runs, 5G NR high-band applications, and environments demanding the lowest possible attenuation.
Each cable class can be terminated with SMA, N-Type, TNC, QMA, or other connectors commonly found on enterprise routers, hotspots, and gateways. Jacket options include indoor PVC and outdoor UV-resistant materials to ensure long-term reliability.
What This Means for You:
Coaxial cable is one of the most influential parts of any antenna system, and understanding cable loss allows you to make better decisions during installation and troubleshooting. Even small changes in cable type or length can significantly improve throughput, reduce connection drops, and enhance the reliability of your entire network. AntennaGear’s AGA-series coax solutions, paired with our antenna and connector selections, provide engineered performance for both simple and advanced RF deployments.