Use RG58 when you need a practical, lower-cost 50-ohm coax cable for a short, general-purpose RF run. Use RG400 when the cable must handle more heat, tighter shielding expectations, aircraft or vehicle routing, higher-frequency acceptance, or a reliability-sensitive installation. Both can appear in similar connectorized cable assemblies, but they are not the same choice once environment, loss budget, and inspection requirements matter.
The simplest rule is this: RG58 is usually enough for short indoor RF jumpers and cost-sensitive antenna leads. RG400 is the safer first sample when failure would be expensive, the cable sits near heat, or the assembly must pass stricter RF checks.
Quick Comparison
| Selection factor | RG58 (GLRG58) | RG400 (GLRG400) |
|---|---|---|
| Impedance | 50 ±2 ohm | 50 ±2 ohm |
| Jacket outer diameter | 4.95 mm | 4.95 mm |
| Dielectric / jacket | Solid PE / PVC | PTFE / FEP |
| Inner conductor | Tinned copper | Silver-plated copper / copper-clad steel, stranded |
| Velocity of propagation | 66% | 69.5% |
| Capacitance | 105.6 pF/m | 95.1 pF/m |
| Peak power | 2.2 kW | 2.1 kW |
| VSWR (specified band) | < 1.20, DC to 3 GHz | < 1.25, DC to 6 GHz |
| Operating temperature | -40 to +85 C | -55 to +200 C |
| Best fit | Short general-purpose RF runs, low-cost antenna leads, bench jumpers | Aircraft, vehicle, heat, better shielding, reliability-sensitive RF assemblies |
These are GlobalRF’s own GLRG58 and GLRG400 specifications. A useful detail: both share the same 4.95 mm jacket diameter, so GLRG400 is effectively a same-size, high-temperature, higher-frequency upgrade from GLRG58. The PTFE dielectric, FEP jacket, and silver-plated conductor are what buy the wider temperature range and the VSWR spec out to 6 GHz. RG names describe a cable family, so always confirm the exact part datasheet before you buy.
What RG58 Is Good For
RG58 is a common 50-ohm coax used in radio, wireless, antenna, and instrumentation applications. GlobalRF’s GLRG58 is a 50-ohm cable with a tinned-copper inner conductor, solid PE insulation, tinned-copper braid, and a PVC jacket at 4.95 mm overall diameter, rated -40 to +85 C with VSWR under 1.20 from DC to 3 GHz.
That makes RG58 a practical fit for short RF cable assemblies where cost and availability matter. It can be used for short antenna leads, radio jumpers, test bench cables, wireless equipment wiring, and general 50-ohm connections.
The important word is short. If the run gets longer, the frequency rises, or the installation is exposed to heat and vibration, RG58 should not be chosen just because it is familiar. Calculate the loss and check the exact cable datasheet before approving it for production.
What RG400 Is Good For
RG400 is usually selected when a buyer wants more reliability headroom than a standard RG58-style cable. GlobalRF’s GLRG400 is a 50-ohm cable with a PTFE dielectric, FEP jacket, silver-plated stranded conductor, 69.5% velocity of propagation, a -55 to +200 C operating range, and VSWR under 1.25 from DC to 6 GHz, all in the same 4.95 mm jacket diameter as GLRG58. That is why it is often chosen as a same-size upgrade when the cable must run hotter, higher in frequency, or under stricter RF inspection.
In practical terms, RG400 is often a better first choice when the cable is routed near heat, used in aircraft or vehicle environments, exposed to vibration, or expected to hold up under stricter RF inspection. It can cost more, but the extra material and shielding margin may be cheaper than troubleshooting intermittent RF loss, noise pickup, or failed acceptance tests later.
Loss, Frequency, and Cable Length
For RF cable selection, the cable name matters less than the total path loss. A 6-inch jumper and a 6-foot cable can behave very differently even when both are made from the same coax family.
RG58 can work well in short runs. It becomes less attractive when the cable is long, the frequency is high, or the system has a tight link budget. RG400 gives more headroom, but it is still not magic. If a design needs a long feeder run, a larger low-loss family such as LMR-195, LMR-240, LMR-400, RG213, or another specified cable may be a better answer than forcing either RG58 or RG400.
Before you choose, define:
| Question | Why it matters |
|---|---|
| What frequency band will the cable carry? | Loss and VSWR behavior change with frequency. |
| How long is the cable assembly? | Loss is length-dependent. |
| What is the maximum acceptable insertion loss? | This decides whether RG58 is enough. |
| Will the cable be near heat, oil, vibration, or outdoor exposure? | Environment can make RG400 worth the cost. |
| Which connectors are required? | The cable is only as good as its termination. |
Heat, Shielding, and Mechanical Reliability
RG58 is usually the economical choice for controlled indoor environments. Its common PVC-jacket constructions are easy to source and flexible enough for many short cable assemblies.
RG400 is the stronger candidate when the installation is less forgiving. Its high-temperature insulation and jacket materials, plus double-shielded construction in common RG400 datasheets, make it a better fit for heat, movement, and RF noise control.
If the cable will sit inside a sealed outdoor box, near an engine bay, behind avionics, close to a transmitter, or anywhere a maintenance team does not want repeat failures, RG400 deserves serious consideration.
Connector Choice Can Decide the Real Performance
An RG58 or RG400 cable assembly can fail because of the connector, not the coax. BNC, SMA, TNC, FME, N-type, FAKRA, and other connector families all have different frequency, mechanical, and installation requirements.
For a reliable custom cable assembly, confirm:
| RFQ detail | Example |
|---|---|
| Cable family | RG58, RG400, or a lower-loss alternative |
| Connector A and B | BNC male to SMA male, TNC to N-type, FME to SMA |
| Cable length | 150 mm, 300 mm, 1 m, custom length |
| Frequency band | VHF, UHF, GPS, LTE, Wi-Fi, test/instrumentation |
| Environment | Indoor, outdoor, vehicle, aircraft, high temperature |
| Target loss | Maximum insertion loss if the system is sensitive |
| Testing | Continuity, VSWR, insertion loss, labeling, packaging |
| Quantity | Prototype, pilot run, production volume |
If you cannot define the connector pair and frequency band, it is too early to approve a cable family.
Cable and connector matching
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When RG58 Is Enough
Choose RG58 when the cable is short, the environment is controlled, and cost matters. It is often the practical choice for short antenna jumpers, simple radio cables, bench test leads, internal device wiring, and general-purpose 50-ohm RF links.
RG58 is also useful when the buyer needs fast sourcing and common connector options such as BNC, SMA, TNC, or FME. For many low-risk assemblies, RG58 is the sensible starting point.
Do not use RG58 by habit when the design has a tight RF loss budget, high heat, vibration, or long cable length. In those cases, check the datasheet and compare RG400 or a lower-loss cable family.
When RG400 Is Worth It
Choose RG400 when the assembly needs better environmental and RF margin. It is often worth the extra cost for aircraft, vehicle electronics, outdoor wireless equipment, higher-temperature routing, high-reliability antenna leads, and test assemblies that must survive handling and inspection.
RG400 may also be the better choice when shielding is important or when the customer already specifies an RG400-style cable for compliance, reliability, or maintenance reasons.
Practical Selection Rule
- If the cable is a short, low-risk indoor jumper, start with RG58.
- If the cable sees heat, vibration, aircraft/vehicle routing, or stricter inspection, start with RG400.
- If the run is long or the loss budget is tight, compare a lower-loss family instead of forcing RG58 or RG400.
- If this is a production assembly, request the cable datasheet, connector drawing, and test report before approval.
FAQ
Is RG58 the same as RG400?
No. Both are 50-ohm coax cable families, but RG58 is commonly used as a general-purpose RF cable, while RG400 is usually selected for higher-temperature, better-shielded, or more reliability-sensitive assemblies.
Can RG400 replace RG58?
Often yes, if the connectors, diameter, bend radius, and assembly requirements are compatible. The reverse is not always safe, because RG58 may not meet the same heat, shielding, or performance expectations.
Is RG58 50 ohm or 75 ohm?
RG58 is a 50-ohm coax family. If the application needs 75-ohm video or CATV-style cable, RG59 or RG6 may be more relevant, depending on the system.
Is RG58 good for antenna cable?
RG58 can work well for short antenna cables and jumpers. For longer runs, higher frequency, or loss-sensitive systems, compare the actual attenuation table before ordering.
Which cable has lower loss, RG58 or RG400?
It depends on the exact construction, frequency, and length, but RG400 is usually chosen when the buyer wants more RF and environmental headroom. Always compare the specific datasheets, not only the RG names.
Which connectors are common for RG58 and RG400?
Common options include BNC, SMA, TNC, FME, N-type, and other RF connector families. The correct connector design, crimp process, and strain relief matter as much as the cable family.
Conclusion
RG58 is the practical choice for short, low-cost, general-purpose 50-ohm RF cable assemblies. RG400 is the safer choice when heat, vibration, shielding, inspection, or reliability matter more than cost.
For a custom RF cable assembly quote, send the cable family, connector pair, length, frequency band, environment, target loss, test requirements, and expected quantity. That information lets an engineering team recommend whether RG58, RG400, or a lower-loss alternative is the right starting point. Browse our RG58 coaxial cable and RG400 coaxial cable, or the full RF cable range.
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