Why cable type matters more than “just use coax”
Engineers often begin with the right connector and the wrong cable. That happens because the phrase “coax cable” sounds specific, but it is really a family name for many controlled-impedance constructions built around different diameters, dielectric materials, shield designs, and mechanical priorities. A cable that works well as a short bench jumper can become the wrong choice for a vibrating machine, a long video backbone, or a compact product with almost no routing space.
If you need a quick refresher on coax construction, start with our coaxial cable fundamentals guide. The short version is that the centre conductor, dielectric, shield, and jacket all work together as a transmission line. When you change cable type, you are changing electrical behaviour and production risk at the same time.
In practical sourcing terms, the first question is not “Which connector fits?” It is “What cable family gives the right electrical performance and survival margin for the actual route?” Once that is fixed, the connector, strip dimensions, ferrule size, bend support, and test plan become much easier to control.
"When a design team gives us only connector names and overall length, the real engineering work has not been done yet. On coax jobs, the cable family decides at least 70 percent of the electrical outcome."
The main types of coaxial cable used in assemblies
Most cable assembly enquiries fall into one of three groups. First are common 50 ohm RF cables for radios, antennas, and instruments. Second are 75 ohm video or broadcast cables for CCTV, SDI, and timing systems. Third are miniature internal cables such as micro-coax, where routing density matters more than field toughness.
RG174
Small 50 ohm coax selected for compact jumpers, pigtails, and short internal or test routes. It solves packaging problems, but the loss climbs quickly as length or frequency increases.
RG316
Another compact 50 ohm option, often chosen when PTFE insulation, moderate heat resistance, and short controlled RF paths are needed.
RG58
The familiar general-purpose 50 ohm cable for radios, instrumentation, and many short antenna leads. It is more forgiving than miniature cables during assembly.
RG400
A higher-spec 50 ohm cable with stronger shielding and a harsher-environment reputation. Commonly chosen where stability matters more than minimum cost.
RG214
Heavy-duty 50 ohm coax for tougher field installations and larger RF routes. It handles abuse better, but it also demands more space and larger connectors.
RG59 and RG6
The most common 75 ohm families for video and broadband-style systems. RG6 normally offers lower loss over longer distances, while RG59 is often easier to handle in shorter or lighter-duty video runs.
Micro-coax
Micro-coax is the answer when standard RG-style cable is physically too large. It appears inside imaging systems, embedded radio products, and tight electronic assemblies where the route is short, the packaging is dense, and processing control must be tight. If that sounds like your use case, our micro-coaxial cable assembly capability is usually more relevant than a generic field cable.
Coaxial cable types comparison table
| Cable type | Impedance | Relative size | Mechanical character | Best fit | Main risk |
|---|---|---|---|---|---|
| RG174 | 50 ohm | Small | Very flexible, light-duty | Compact jumpers, internal routing, test leads | Higher loss and easier shield damage during prep |
| RG316 | 50 ohm | Small | Flexible with PTFE insulation | Bench RF leads, short internal pigtails, moderate heat | Short-run cable, not ideal for long-distance loss budgets |
| RG58 | 50 ohm | Medium | General-purpose balance of cost and handling | Radios, instrumentation, antenna jumpers | Too bulky for dense routing and not the lowest-loss option |
| RG400 | 50 ohm | Medium | Higher reliability, double shield, wide temp range | Defence, motorsport, aerospace, harsh-duty RF | Higher cost and stiffer routing than miniature coax |
| RG214 | 50 ohm | Large | Heavy-duty and well shielded | Longer RF runs, outdoor feeders, tougher field installs | Large bend radius and connector bulk |
| RG59 | 75 ohm | Medium | Video-oriented, easier to handle than RG6 | CCTV, SDI, legacy video, timing distribution | Wrong choice for a 50 ohm RF system |
| RG6 | 75 ohm | Medium to large | Lower loss for longer video/data runs | Broadcast, CCTV backbone, broadband-style distribution | Too stiff or oversized for compact equipment |
| Micro-coax | Usually 50 ohm | Very small | Excellent for dense internal routing | Imaging, compact electronics, embedded antennas | Processing tolerance is tight and field abuse tolerance is low |
Four selection rules that prevent the wrong cable choice
1. Start with impedance and system type
Split the decision into 50 ohm RF systems and 75 ohm video systems first. That one step removes most bad substitutions before you waste time comparing jacket colours, pricing, or connector shape.
2. Define the loss budget before choosing the smallest cable
Small cables solve routing problems but pay for it in attenuation. If the link budget allows only 3 dB total loss, an undersized cable may fail the design long before anyone notices during continuity testing.
3. Match cable type to connector family, not just impedance
Two cables can both be 50 ohm and still require different ferrules, centre contacts, strip dimensions, and crimp dies. Our BNC connector guide and RF connector types guide show why cable-plus-connector should be treated as one system.
4. Include handling conditions in the selection decision
Static bench leads, moving robotics cables, outdoor feeders, and sealed enclosure jumpers are different products even when they share impedance. Bend support, clamp spacing, and exit strain relief matter as much as the cable family itself.
"If the route flexes repeatedly, we stop treating coax as a static RF part and start treating it as a motion assembly. A cable that looks perfect on day one can fail before 100,000 cycles if the bend support is wrong."
50 ohm vs 75 ohm: where coax types usually divide
Many “types of coaxial cable” questions are really impedance questions. A coaxial cable can look similar from the outside while being designed around a different characteristic impedance inside. That is why RG58, RG316, RG400, and RG214 are usually discussed in 50 ohm systems, while RG59 and RG6 are normally discussed in 75 ohm systems.
In RF equipment, 50 ohm remains the default because it balances power handling, attenuation, and common instrument design. In CCTV, SDI, and many video-distribution paths, 75 ohm remains the standard because it delivers low attenuation for that class of signal path. When a buyer mixes the two, the result may still pass continuity yet create reflections, margin loss, or intermittent signal quality faults.
Special constructions such as triaxial cable or twinaxial cable may appear in specialised systems, but those are not general substitutes for the mainstream RG families above. If a drawing requires them, the complete cable and connector series should be locked before purchasing starts.
Common buying mistakes when comparing coax cable types
Choosing by diameter alone
A small cable is not automatically the best cable. Miniature coax often solves packaging but can destroy the loss budget or reduce process margin.
Assuming all 50 ohm cables are interchangeable
Connector fit, braid style, dielectric stability, and bend performance vary a lot between families even when impedance matches.
Using continuity as the only acceptance test
Continuity proves the cable is connected. It does not prove insertion loss, return loss, shield integrity, or long-term flex reliability.
Ignoring strain relief and bend support
Even the right cable family can fail early if the exit from the connector is unsupported. See our strain relief guide for the mechanical side of the same problem.
"Strip control is where coax assembly quality becomes visible. If strip variation is more than about 0.5 mm on a small RF cable, the risk of poor pin retention, exposed braid, or dielectric movement rises fast."
How to specify the right coaxial cable type for a supplier
A usable enquiry should identify the cable family explicitly, not just the word “coax.” For example, “RG400, 50 ohm, SMA male to bulkhead SMA female, 1.2 m, outdoor telecom enclosure, insertion loss verification at operating frequency” is a usable start. “Need a coax lead with SMA on both ends” is not.
Minimum information to send
- Exact cable family, such as RG58, RG400, RG6, or micro-coax
- System impedance and operating frequency or data-rate target
- Connector series on each end and any angle or bulkhead requirement
- Finished length, tolerance, route constraints, and minimum bend space
- Environmental requirements such as motion, moisture, abrasion, or temperature
- Test method: continuity only, VSWR, insertion loss, pull force, or functional verification
If the application is closer to a complete RF program than a simple jumper, involve cable and connector selection together. That avoids the usual late-stage problem where a preferred cable family does not fit the intended connector body or bend envelope.
Frequently asked questions
What are the most common types of coaxial cable?
The most common coaxial cable types in production assemblies are RG58, RG174, RG316, RG400, RG214, RG59, RG6, and micro-coax. In practical terms, most buying decisions start by separating 50 ohm RF cables from 75 ohm video cables, then narrowing by diameter, bend radius, shielding, and insertion-loss limit in dB.
What is the difference between RG58 and RG174 coax?
RG58 is a thicker 50 ohm cable typically chosen when you need more mechanical robustness and lower loss than miniature jumper cable. RG174 is much smaller and easier to route in compact equipment, but its attenuation is higher and its shield is easier to damage during stripping. If the assembly is under 1 to 2 metres and routing space is tight, RG174 may fit. For longer runs or rougher handling, RG58 is usually safer.
When should I use RG400 instead of RG316?
Use RG400 when the project needs a 50 ohm coax with better temperature resistance, stronger shielding, and lower loss than RG316. RG400 is commonly selected for aerospace, defence, motorsport, and high-reliability industrial systems. RG316 is smaller and more flexible for short internal or bench assemblies, but RG400 normally tolerates harsher environments and longer runs.
Can I use 75 ohm coax in a 50 ohm RF system?
Not as a default. Mixing 75 ohm and 50 ohm coax introduces an impedance mismatch of about 1.5:1 VSWR, which may be unacceptable in radios, measurement equipment, and controlled RF links. A 75 ohm cable such as RG59 or RG6 belongs in video, CCTV, and broadcast-style systems unless the full design explicitly allows the mismatch.
Which coaxial cable type is best for flexible moving applications?
No single cable is best for every flexing application. Small-diameter coax such as RG174 or micro-coax may bend easily, but repeated motion can still break the centre conductor or shield if the cable lacks the right stranding and strain relief. For moving equipment, specify minimum bend radius, cycle target, and support method together. A dynamic cable that must survive 100,000 flex cycles should not be chosen from diameter alone.
What information should I send when asking for a coax cable assembly quote?
Send at least 8 items: connector A, connector B, cable family, system impedance, finished length, operating frequency or data rate, installation environment, and test expectation. If any of those are missing, the supplier may still quote the job, but the technical risk moves into production and field validation.
Related coax and RF resources
What Is a Coaxial Cable?
Start with coax construction, shielding, and impedance basics before comparing cable families.
BNC Connector Types
Compare the connector side of the system before pairing BNC bodies with a cable family.
RF Connector Types Guide
Choose SMA, BNC, TNC, N-type, and other RF interfaces that match the cable and application.
The best coax type is the one that matches the route, not the one that sounds familiar
RG58, RG174, RG316, RG400, RG214, RG59, RG6, and micro-coax all have a place. The right choice depends on impedance, allowable loss, available bend space, connector fit, and service environment. Lock those inputs first, then release the assembly as a controlled cable-plus-connector system.