Coaxial Cable Loss Chart by Frequency and Cable Type

If you source RF cable assemblies, one of the fastest ways to lose signal margin is to choose cable by outside diameter alone. A coax that looks convenient on the drawing can become expensive once the frequency rises and the run length is real. That is why buyers should review attenuation early, not after the harness is already routed.

For background, see coaxial cable, decibel, and standing wave ratio. If your program also needs connector selection, harness support, or drawing-controlled build documentation, review our cable assembly guide, bespoke cable manufacturers, low volume wire harness assembly, and our related Fakra vs Mini-Fakra automotive RF connector guide.

What a coax loss chart actually tells you

A cable loss chart shows how much signal is attenuated as frequency increases over a standard length such as 100 meters or 100 feet. In real sourcing work, that chart is not just an electrical curiosity. It tells you whether a given cable can survive the required band without turning the assembly into a heater.

As a rule, attenuation climbs with frequency, and thinner cables usually lose more than larger low-loss families. The exact number also depends on conductor construction, dielectric system, shield design, temperature, and the published test method. That is why a good comparison should always name the cable family and the source of the published point.

"Once feeder loss reaches 3 dB, you have already thrown away roughly 50% of the signal power before connector mismatch, adapter loss, or antenna inefficiency are counted. Buyers should treat 3 dB as a design checkpoint, not a rounding error."
— Hommer Zhao, Technical Director

For planning purposes, use charts to compare options. For release, quote against the exact part number and the exact operating band. A cable family name alone is not enough when the assembly will be tested for insertion loss or VSWR.

Coaxial cable loss chart: common cable families

The table below combines typical published attenuation checkpoints from Belden RG-type datasheets and Times Microwave LMR-family datasheets. Because vendors do not always publish the same frequency points, the chart mixes 200 to 220 MHz, 900 to 1000 MHz, and 2.4 to 2.5 GHz published checkpoints. Use it for sizing decisions, then verify the exact part before purchase.

Cable type	Approx. OD	Published loss near 200-220 MHz (dB/100m)	Published loss near 900-1000 MHz (dB/100m)	Published loss near 2.4-2.5 GHz (dB/100m)	Practical takeaway
RG-174 type	2.8 mm	42 at 200 MHz	110 at 1000 MHz	Vendor point not listed in cited sheet	Good only for very short jumpers where flexibility matters more than efficiency
RG-58 type	4.95 mm	23 at 200 MHz	60 at 1000 MHz	Vendor point not listed in cited sheet	Acceptable for short runs, but loss rises quickly in cellular and Wi-Fi bands
LMR-100A	2.79 mm	35.8 at 220 MHz	74.9 at 900 MHz	130.6 at 2500 MHz	Better than many small RG jumpers, but still expensive in dB on long runs
LMR-240	6.10 mm	12.0 at 220 MHz	24.8 at 900 MHz	42.4 at 2500 MHz	Strong middle-ground choice for moderate feeder runs and compact assemblies
LMR-400	10.29 mm	6.1 at 220 MHz	12.8 at 900 MHz	22.2 at 2500 MHz	Preferred when low loss matters more than routing convenience

Even with mixed publication points, the directional lesson is clear. Small cable saves space but burns margin fast. Larger low-loss families become more attractive as soon as the run length, power level, or receiver sensitivity gets tight.

Why frequency changes the buying decision

At 30 MHz or 50 MHz, several cable families may look acceptable. At 900 MHz, the ranking starts to separate sharply. At 2.4 GHz and above, cable choice becomes a system-level decision because every extra meter compounds the attenuation penalty.

That matters in automotive telematics, GNSS, camera backhaul, test equipment, wireless gateways, and industrial radio assemblies. A cable that looks fine at prototype length can fail the production use case once routing grows from 0.3 m to 3 m or 5 m.

For example, if you compare LMR-240 and LMR-400 at approximately 2.5 GHz, the published values above differ by about 20.2 dB per 100 m. That is roughly 0.202 dB per meter of improvement for LMR-400 over the same normalized length. On a 10 m run, that difference is about 2 dB, which is not small in a real RF budget.

"The buyer mistake is usually not choosing the worst cable. It is choosing a cable that is only 1 to 2 dB too lossy after routing, adapters, and manufacturing tolerance are included. That small paper gap is enough to create flaky field performance."
— Hommer Zhao, Technical Director

When the application includes tight receive sensitivity or small transmit power margins, treat every decibel as a budgeted resource. If the assembly is feeding a roof antenna, camera module, telematics unit, or enclosure-mounted radio, the cable loss number should appear in the drawing review just like bend radius and connector keying.

Length matters as much as cable family

Published charts are normalized, usually to 100 m or 100 ft. Real assemblies are shorter, so buyers need to convert the chart into actual run loss. The arithmetic is straightforward:

actual loss = published loss x actual length / normalized length

If a cable is published at 24.8 dB/100m near 900 MHz and your run is 8 m, the cable contribution is about 1.98 dB before connectors and mismatch are added. If each connector pair adds another 0.1 to 0.2 dB in practice, the total path starts moving quickly.

That is where our dB calculator helps. It is also useful to pair attenuation review with the frequency to wavelength calculator when the assembly is part of an antenna or RF distribution problem.

Buyers should be especially careful with these situations:

• long feeder runs above 700 MHz
• multiple inline adapters or bulkhead transitions
• compact enclosures that force tight bends behind the connector
• low-power radios where link margin is already thin
• prototypes that later grow in length during packaging release

Loss is not the only cable criterion

Attenuation gets the headline, but it is not the only reason one coax family outperforms another in production. A cable that looks great on paper can still be the wrong choice if it is too stiff, too large for the backshell, or incompatible with the planned connector termination method.

The complete selection should consider:

• attenuation across the actual operating band
• minimum bend radius and routed packaging space
• connector compatibility and available crimp or solder process
• shielding effectiveness and EMI exposure nearby
• environmental exposure such as oil, UV, vibration, or door motion
• required return loss or VSWR limit after assembly
• production test method and acceptable insertion-loss threshold

That is why many OEM teams do not buy bulk cable and connector parts separately at the last minute. They release a controlled cable assembly package that defines cable family, connectors, length, routing, test criteria, and approved alternates together.

"For a custom RF assembly, I would rather receive one drawing with cable type, connector series, length tolerance, and insertion-loss limit than five emails about 'something similar to RG-58.' That single drawing can remove days from quoting and prevent the wrong cable from reaching production."
— Hommer Zhao, Technical Director

If the build is part of a broader interconnect or electronics program, it also helps to align the cable spec with the rest of the release package used for turnkey electronics manufacturing or legacy obsolete connector replacement work.

How to use a coax loss chart when writing a specification

A useful RF cable assembly specification should not stop at a family label such as "RG-58" or "LMR-240 equivalent." It should define the actual design intent. A better release package usually includes:

1. Exact cable family or approved part number range.
2. Operating band, such as 400 to 900 MHz or 2.4 to 2.5 GHz.
3. Maximum insertion loss over the finished assembly length.
4. Return loss or VSWR target, especially above 1 GHz.
5. Connector family, polarity, keying, and any adapter exclusions.
6. Length tolerance, bend restrictions, and strain-relief direction.
7. Required tests such as continuity, pinout, insertion loss, return loss, and visual inspection.

This is where buyers separate catalog shopping from engineering release. The more exact the spec, the fewer quoting loops you will have, and the easier it becomes to compare suppliers on a like-for-like basis.

Practical decision guide by cable size

Use small coax such as RG-174 class or LMR-100A class when:

• the run is short
• packaging is tight
• the assembly is an internal jumper rather than a long feeder
• flexibility and small connector size matter more than minimum loss

Use mid-size coax such as LMR-240 class when:

• the run length is moderate
• the band is already in the high hundreds of MHz or low GHz range
• the assembly still needs manageable routing in cabinets, vehicles, or compact boxes

Use larger low-loss coax such as LMR-400 class when:

• the run is long
• the frequency is high enough that every dB matters
• the product has limited RF margin or the antenna is physically distant from the radio
• the routing envelope can tolerate the larger bend radius and outer diameter

The correct answer often comes from balancing mechanical packaging against electrical budget, not from maximizing one variable alone.

FAQ

Q: Which coax cable type has the lowest loss for longer RF runs?

Among the cable families compared here, LMR-400 class cable has the lowest published attenuation, at about 12.8 dB/100m near 900 MHz and 22.2 dB/100m near 2.5 GHz. That makes it a common choice when the run is several meters and signal budget is tight.

Q: Is RG-174 suitable for 2.4 GHz cable assemblies?

It can be used for very short jumpers, but buyers should be cautious. The cited RG-174 sheet already shows 110 dB/100m at 1000 MHz, which signals very high attenuation by the time the band reaches 2.4 GHz. For anything beyond a short internal assembly, a lower-loss family is usually safer.

Q: How do I convert a cable loss chart to the actual assembly length?

Multiply the published dB figure by the actual cable length and divide by the chart's normalized length. For example, a cable rated at 24.8 dB/100m will contribute about 2.48 dB over 10 m, before connector loss and mismatch are included.

Q: Why do some coax charts use 100 feet while others use 100 meters?

Both formats are common. North American RF datasheets often use 100 ft, while many catalog and European documents use 100 m. Always normalize before comparing. A 3.9 dB/100 ft value is not directly comparable to 3.9 dB/100 m because the meter-based number represents a much longer distance.

Q: Should buyers choose cable only by attenuation?

No. Attenuation is critical, but the final selection also depends on bend radius, connector compatibility, shielding, environment, and assembly test limits. A lower-loss cable that cannot be routed or terminated correctly can still be the wrong production choice.

Q: What should be on an RF cable assembly drawing besides the cable type?

At minimum, define the exact cable family, length tolerance, connector series, operating band, and test requirement. For many assemblies above 1 GHz, add insertion-loss and return-loss limits so the supplier is measured against a clear electrical target rather than continuity alone.

Final takeaway

A coaxial cable loss chart is one of the most useful early filters in RF sourcing because it turns vague cable preferences into measurable tradeoffs. Thin coax families win on flexibility and packaging, while larger low-loss families protect the signal budget as frequency and length increase.

If you need help selecting a cable family, building a custom RF harness, or defining loss and VSWR limits for production, contact our team. We can review the assembly length, frequency band, connector stack, and test plan before the quote turns into expensive rework.