RG11 coax is generally a 75-ohm cable for television and broadband distribution, while RG-8/U and RG-8X are 50-ohm cables for radio and antenna systems. Their similar names and large round profiles do not make them interchangeable.

Choose the impedance required by the equipment first. Then compare attenuation at the operating frequency, run length, conductor size, power rating, flexibility, and connector fit. A larger cable is not automatically the correct replacement for a smaller one.

75-Ohm TV or 50-Ohm Radio? Start With the Signal System

Television antennas, cable distribution equipment, satellite receivers, and most video equipment use a 75-ohm system. RG11 is intended for that environment, as are other 75-ohm coaxial cable types such as RG6. RG-8/U and RG-8X belong to the 50-ohm family used with radio transmitters, transceivers, and many communications antennas.

Connecting 50-ohm cable to 75-ohm equipment may produce a usable receive signal over a short run, but the impedance mismatch creates reflections and can affect system performance. In a transmitting system, it can increase standing-wave ratio and reduce the power delivered to the antenna. Conversely, replacing a 50-ohm radio feed line with RG11 solely because it has a similar diameter is not a sound substitution.

• 75-ohm TV and video: RG11, RG6, and matching 75-ohm connectors.
• 50-ohm radio: RG-8/U or RG-8X, with connectors and equipment designed for 50 ohms.

Impedance establishes compatibility; the cable’s construction and datasheet determine loss, frequency range, and safe power handling.

RG11 Coax: Construction, Diameter, Loss, and TV Run Limits

Typical RG11 has a nominal outside diameter of about 0.405 inch, making it substantially larger and less flexible than RG6. Common versions use a 14-AWG copper-clad-steel center conductor, a foam polyethylene dielectric, and an aluminum foil-and-braid shield. Exact conductor material, shield coverage, and weatherproofing vary by manufacturer.

The larger conductor and dielectric generally provide lower attenuation than smaller 75-ohm cable over long television runs. A conventional RG11 may show roughly 1 to 1.5 dB of loss per 100 feet around 100 MHz, with considerably more loss at higher frequencies. At 500 MHz or 1 GHz, use the manufacturer’s attenuation chart rather than applying the low-frequency figure.

RG11 is useful for long antenna, CATV, broadband, and some satellite distribution runs where preserving signal level matters. Its drawbacks are stiffness, a larger minimum bend radius, and more difficult termination. F compression connectors are common, but they must be sized for the exact RG11 diameter and dielectric. Some systems use specialized 75-ohm BNC or other connectors.

RG11 is not a general-purpose high-power radio cable. Its 75-ohm impedance and typical copper-clad-steel construction make it suitable for television distribution, not as a drop-in replacement for a 50-ohm transmitter feed.

RG-8/U Coax: Construction, Power Handling, and Radio Use

RG-8/U is a large 50-ohm radio cable, also commonly measuring about 0.405 inch in diameter. Traditional versions use a roughly 10-AWG solid copper center conductor, a polyethylene dielectric, and a braided shield. Modern products carrying the RG-8/U designation may use different copper, dielectric, or shield constructions, so the product specification controls.

Its larger center conductor and greater dielectric volume usually produce lower loss and higher power capacity than RG-8X. Representative RG-8/U loss can be near 1 dB per 100 feet at 100 MHz, but the value rises with frequency and varies widely among standard and low-loss designs. A 200-foot run has approximately twice the cable loss of a 100-foot run at the same frequency.

Use RG-8/U for fixed antenna feeders, base-station installations, HF equipment, and many VHF or UHF radio systems when the run is long enough for low attenuation to justify its size. It is stiff and heavy, so it needs proper supports and a generous bend radius. The larger conductor also makes it more suitable for higher-power transmission than RG-8X, although the allowable power depends on frequency, SWR, temperature, and connector quality.

N-type connectors are a common choice for demanding outdoor or higher-frequency installations. PL-259, TNC, and other 50-ohm connectors may also be used when specifically rated and sized for RG-8/U. A connector intended for RG-58 or RG-8X will not necessarily fit.

RG-8X Coax: Flexibility, Connector Fit, Frequency, and Run Length

RG-8X is a smaller, more flexible 50-ohm cable, usually about 0.242 inch in diameter. Common designs use a 16-AWG stranded or solid center conductor, foam polyethylene insulation, and a foil-and-braid shield. The reduced diameter makes it easier to route through vehicles, portable stations, and crowded equipment panels, but it also increases attenuation and reduces power capacity.

At around 100 MHz, a typical RG-8X may lose roughly 2 dB per 100 feet—often about twice the loss of a conventional large 50-ohm cable. Loss rises sharply as frequency increases, so RG-8X is best for short jumpers, mobile installations, portable HF stations, and moderate-length VHF runs. For UHF or a long antenna feed, check the exact attenuation chart before choosing it.

RG-8X commonly accepts connectors made specifically for its smaller outside diameter, including selected BNC, N, TNC, and UHF designs. Some PL-259 connectors require an RG-8X reducer or adapter. Connector family alone does not guarantee a proper fit: match the connector to the cable diameter, center conductor, shield, and impedance.

For a short, flexible 50-ohm run, RG-8X is often the practical choice. For a long or high-power radio feed, RG-8/U or a modern low-loss 50-ohm cable is usually better. For a 75-ohm television run, use RG11 or another specified 75-ohm coaxial cable instead.