RF Cable Types: A Practical Guide to Coax Styles, Signal Loss and Selection

A 1 m RG58 jumper costs you about 1 dB at 2.4 GHz, which is roughly 20% of the power going in. Swap it for a 0.141 in semi-rigid cable and the same run loses a little over half that. Nothing else in the assembly changed — only the cable type did.

That is why the cable family is usually the first decision worth getting right when comparing RF cable types. Impedance decides what the cable is allowed to connect to, construction decides how much signal reaches the far end, and the connector interface caps the frequency the finished assembly can carry. What follows covers how the families differ, what datasheet numbers actually mean, and where orders most often go wrong.

Content

1 The main RF cable types, compared
2 Impedance comes first: 50 or 75 ohm
- 2.1 50 ohm
- 2.2 75 ohm
3 Inside the cable: four layers, four jobs
4 Reading loss figures without getting fooled
5 Connector interfaces set the ceiling
6 Matching cable to connector and to the job
7 Five details that cause rework
8 Frequently asked questions

The main RF cable types, compared

Nearly every catalogue cable falls into one of five families. They overlap in impedance and connector options, so the real differences come down to loss for a given diameter, how tight you can bend them, and whether the run will ever be re-routed.

Indicative attenuation at 1 GHz for common 50-ohm families; values shift with diameter, dielectric and manufacturer, so confirm against the supplier datasheet.
Family	Typical sizes	Loss at 1 GHz (dB/m)	Best suited to	Main trade-off
Flexible (RG-style)	RG316, RG58, RG213, 1.9–10.3 mm	0.3–1.2	Bench jumpers, short runs, lab patching	Highest loss for a given diameter
Low-loss flexible	0.240 in, 0.400 in, foam or air-spaced	0.1–0.45	Antenna feeders, in-building runs	Stiffer jacket, wider bend radius
Semi-rigid	.047–.250 in, solid PTFE, copper tube	0.2–1.2	Phase-critical paths, dense internal routing	Cannot be re-routed after forming
Conformable	.086–.250 in, hand-formable	0.25–1.0	Tight enclosures, prototype routing	Less repeatable, shorter flex life
Corrugated (hardline)	1/2 in, 7/8 in	0.05–0.15	Long feeders, high power, outdoor runs	Bend radius and connector cost

Over a 10 m run at 2 GHz, RG58 loses roughly 9 dB where 0.240 in low-loss cable loses about 3 dB. That gap comes from the dielectric and the shield, not from the copper.

Impedance comes first: 50 or 75 ohm

Two impedances cover almost all RF work, and they are not interchangeable.

50 ohm

Wireless, radar, GPS, test instruments
Standard for SMA, N, TNC and 2.4 mm interfaces
Default for anything carrying a modulated signal

75 ohm

Broadcast video, CATV, satellite IF distribution
Common in BNC and F connectors
N-type is rarely produced in 75 ohm

A 75-ohm plug on a 50-ohm jack does not fail outright — it reflects. The joint adds return loss, the source sees a worse load, and a sweep shows ripple that often gets blamed on the cable. Mixing is easiest to get wrong with BNC, where the 50 and 75 ohm versions look identical from the outside and differ only in the dielectric and centre pin.

Inside the cable: four layers, four jobs

Each layer moves a different number on the datasheet, which is why two cables with the same impedance can behave very differently.

Cut-away view of a coaxial cable: the dielectric sets loss and velocity factor, the shield sets leakage and screening.

Centre conductor: solid copper for lowest loss and stable phase; stranded for flex life.
Dielectric: solid PE (velocity factor about 0.66) is cheap and stable, foamed PE (0.80–0.88) cuts loss but is softer, solid PTFE (about 0.70) handles heat and suits semi-rigid builds.
Shield: a single braid gives 90–95% coverage, while foil plus braid approaches full coverage and improves screening at high frequency — at the cost of stiffness.
Jacket: PVC indoors, FEP for temperature and chemical resistance, TPU for outdoor abrasion.

Velocity factor is the item buyers most often skip. A solid-PE cable with a factor of 0.66 is electrically 1.5 times its physical length, so 3 m of coax behaves like 4.5 m of free space. That matters for phase-matched pairs, delay lines and antenna harnesses, where two cables of equal physical length can still arrive out of step if their dielectrics differ.

Reading loss figures without getting fooled

Datasheet attenuation is measured on a swept analyser at room temperature into matched 50-ohm loads, and quoted either in dB per 100 ft or dB per 100 m. Unit conversion is where mistakes creep in: 0.5 dB/100 ft is the same cable as 1.6 dB/100 m, yet the two numbers look far apart on a quotation sheet.

Indicative attenuation at 1 GHz, dB per metre. Figures are typical published values and vary by tolerance and construction.

Attenuation versus frequency, in dB per metre, assuming loss rises with the square root of frequency.

Loss climbs roughly with the square root of frequency, so a cable quoted at 1 GHz is about 2.4 times lossier at 6 GHz. If the link runs at 3.5 GHz, ask for attenuation at 3.5 GHz rather than the headline number, and confirm the tolerance — plus or minus 5% between production lots is normal.

Super Low-Loss Flexible RF Cable AssemblyPre-terminated assembly for high-frequency links, offering ultra-low insertion loss and stable phase performance where every decibel matters.View Product →

When every tenth of a decibel counts, a pre-terminated super low-loss flexible assembly removes both the crimp and the guesswork from that calculation.

Connector interfaces set the ceiling

The interface caps the assembly. An SMA-terminated cable will not deliver 40 GHz simply because the coax is rated higher — the connector's upper limit governs, and so does the launch into the board or module it mates with.

Typical maximum operating frequency for common 50-ohm interfaces; the real limit depends on the specific connector body, cable and launch.
Interface	Typical maximum	Common cable pairing	Notes
BNC	4 GHz	RG58, RG174	Bayonet coupling, quick lab patching
TNC	11 GHz	RG58, RG316	Threaded BNC variant, better under vibration
N-type	11–18 GHz	0.400 in, 1/2 in corrugated	Outdoor feeders, medium power
SMA	26.5 GHz	.141 in semi-rigid, RG316	Most common microwave interface
2.4 mm	50 GHz	.086 in, .141 in	Precision test, instrument ports
1.85 mm	67 GHz	.047–.086 in	High-frequency instruments and modules

Choose the interface first, then the cable that fits it. Each connector body is machined for a defined range of cable diameters, so a connector built for RG58 will not seat on 0.240 in low-loss cable even though both are 50 ohm.

SMA RF Coaxial Connector SeriesThreaded 50Ω connectors covering DC–26.5 GHz, with male and female variants and cable compatibility tables for matching interfaces to assemblies.View Product →

SMA remains the workhorse of bench and microwave work, which is why it appears in so many of the assemblies we build.

Matching cable to connector and to the job

Most selection arguments disappear once the application is named. These pairings cover the majority of orders:

Bench and lab, under 1 m: RG316 or RG58 with SMA. A few tenths of a decibel hardly matter next to flexibility and cost.
Outdoor feeder, 10–50 m: 0.400 in low-loss or 1/2 in corrugated with N-type. Weatherproofing the joint matters more than the last 0.3 dB.
Phase-critical harness: semi-rigid, or flexible cable supplied as a phase-matched set with a stated tolerance in degrees at a stated frequency.
Low-PIM sites: assemblies specified by PIM value under a two-tone test, usually around -150 dBc, rather than by insertion loss alone.
Bulkhead, vacuum or pressure boundary: hermetically sealed connectors and glass-to-metal seals where the joint has to hold pressure as well as signal.

If crimping in-house is not practical, pre-terminated assemblies arrive tested and labelled; this overview of what RF cable assemblies do covers the extra checks that come with them.

N-Type RF Coaxial Connector SeriesThreaded 50Ω and 75Ω connectors rated to DC–18 GHz and DC–3 GHz, suited to feeder runs that face weather, torque and repeated mating.View Product →

For feeder runs, the N-type body is usually the deciding part of the bill of materials, since it must survive weather, torque and repeated mating.

Five details that cause rework

Mixing dB/100 ft and dB/100 m on the same comparison sheet. Convert everything first, then compare.
Quoting a matched pair by length alone. Velocity factor has to match too, or the pair is only matched at one frequency.
Ordering a connector without checking its cable group. The datasheet lists the cable types the body was machined for.
Ignoring bend radius. A kink changes impedance permanently; flexible cables are commonly quoted at ten times the outer diameter.
Leaving temperature and ingress unstated. A PVC jacket is fine indoors and a poor choice on a mast, while FEP or TPU usually costs very little more.

Frequently asked questions

What are the different types of coaxial cable?

The main RF cable types are flexible RG-style, low-loss flexible, semi-rigid, conformable and corrugated hardline, each split again by impedance and diameter.

Is 50 ohm better than 75 ohm?

Neither is better. 50 ohm suits wireless, radar and test gear; 75 ohm suits video and CATV distribution. Mixing the two causes reflections at the joint.

What is the difference between RG58 and RG316?

Both are 50-ohm flexible cables, but RG316 is about 2.5 mm in diameter with a PTFE dielectric, while RG58 is roughly 5 mm with solid PE. RG316 bends tighter and loses more per metre.

Which RF cable type has the lowest loss?

Large corrugated hardline is lowest, typically well under 0.15 dB/m at 1 GHz. Among small cables, 0.400 in low-loss flexible is usually the practical choice.

Can I use an SMA connector on RG58 cable?

Only with a connector body machined for that cable group. SMA is made in several sizes for different diameters, and the wrong one will not crimp correctly or hold impedance.

What is a low-PIM cable assembly used for?

Low-PIM assemblies are used where weak signals share a site with strong transmitters, such as cellular installations. They keep passive intermodulation below a specified limit, usually around -150 dBc.