Published on 10/13/2026
RG178 and RG196 are miniature nominal 50 Ω coaxial cable families used when an RF connection must fit a small route. The exact jacket, diameter and ratings vary: the RG178 reference here is 1.8 mm FEP-jacketed cable, while RG196 examples include 1.71 mm FEP and 2.05 mm PTFE-jacketed constructions. Do not select by family name alone.
A 200 mm internal jumper may tolerate micro-coax loss that would be unacceptable over 2 m. Small cable also creates a mechanical problem: a tiny termination needs protection against pulling, sharp bends and side loads. The smallest cable is not automatically the safest design.
This guide compares exact published constructions and keeps cable-only data separate from finished assemblies. SigmaRF can build miniature RF cable assemblies to a drawing; confirm the approved cable, connector variants and operating band before release.
On This Page
| Property | RG178 reference 83265 | RG196 FEP example | RG196 A/U PTFE example |
|---|---|---|---|
| Diameter | 1.8 mm | 1.71 mm | 2.05 mm |
| Dielectric / jacket | PTFE / FEP | PTFE / FEP | PTFE / PTFE |
| Center conductor | 30 AWG stranded silver-plated copper-clad steel | 7 x 0.102 mm silver-plated copper-clad steel | 7 x 0.10 mm, silver-plated conductor listed |
| Nominal impedance | 50 Ω | 50 Ω | 50 Ω ±2 Ω |
| Velocity factor | 70% | 70% | 70% |
| Capacitance | 95 pF/m | 96.5 pF/m | 95 pF/m |
The family comparison is not a ranking by size. RG196 is not universally smaller than RG178: the PTFE-jacketed example is larger than the RG178 reference. Connector fit depends on conductor, dielectric and shield dimensions as well as overall diameter.
Key idea: Micro-coax is a size description, not a single cable standard. Define the part and its construction on the drawing.
Use the selected part's nominal attenuation and keep units consistent. This chart shows published cable loss in dB/m, not maximum assembly insertion loss.
| Frequency | RG178 reference dB/m | RG196 FEP example dB/m | RG196 PTFE example dB/m |
|---|---|---|---|
| 100 MHz | 0.459 | 0.453 | 0.449 |
| 400 MHz | 0.919 | 0.912 | 0.920 |
| 1000 MHz | 1.509 | 1.457 | 1.520 |
At 1 GHz, 200 mm of the RG178 reference contributes about 0.302 dB of nominal cable loss. A 2 m run contributes about 3.018 dB before connectors. When length grows, revisit the cable selection rather than relying on a successful short prototype.
The RG196 FEP sheet states a 3 GHz maximum operating frequency, but that does not rate every RG196 connectorized assembly to 3 GHz. The same sheet lists an unusually high +250 °C limit. That number is not adopted here as a general or approved assembly rating; obtain confirmation for the exact construction and material stack.
⚠️ Do not mix temperature, bend or voltage values from different RG196 sheets into one specification. Resolve part-specific discrepancies before procurement.
Miniature RF cable fits short panel-to-module links, compact receiver paths and small fixtures when the electrical budget permits. It is less suitable when the cable must carry mechanical loads, run a long distance or undergo uncontrolled repeated movement.
Compact receiver linksShort antenna leadsPanel-to-module routesMiniature fixtures
Use a miniature construction
The run is short, the connector accepts the exact cable and the route protects the termination.
Use another cable
The job needs lower feeder loss, qualified dynamic flexing, more mechanical strength or tighter phase stability.
The RG178 reference lists a 25 mm installation bend radius. A separate RG196 FEP sheet lists 10 mm without distinguishing bend categories. Do not treat those as interchangeable or as proof of flex-cycle life. Use the approved product instructions and keep bends away from connector exits. See SigmaRF's cable selection and assembly design guides for the broader decision.
Specify the complete RF assembly
Send the frequency band, connector interfaces, finished length and routing drawing. SigmaRF can match the cable and terminations to your application.
Step 01
Approve cable and connector parts
Name the miniature cable part and compatible connector cable group. Define interface family, polarity, male/female and angle. Not every small connector can accept every thin cable.
Step 02
Control routing and strain relief
Show finished length in mm, tolerance and bend route. Prevent pinch points and side loads. Give small snap-on interfaces support rather than letting cable handling stress the PCB.
Step 03
Define test limits
Specify VSWR and insertion loss across the operating band, reference planes and required reports. Add continuity, insulation and mechanical checks as the application requires.
SigmaRF VNA-sweeps every assembly for VSWR and insertion loss before shipment. Its overall RF assembly capability spans 100 MHz to 40 GHz across suitable cable and connector systems, not every product discussed here. Volume work is supported in Vadodara, India, with precision work in the Cleveland area, USA. Lead times can be as short as 2 days for suitable builds, subject to parts, quantity and the agreed specification.
The company-wide 40 GHz capability is not an RG178 or RG196 rating. For repeat orders, retain cable, connector and termination details. SigmaRF's VNA measurement guide covers loss verification; the PCB-to-antenna guide covers small-interface reliability.
Assume a 200 mm RG178 jumper at 1 GHz using nominal 46 dB/100 ft. Add hypothetical 0.05 dB per connector. These allowances are design assumptions, not measured SigmaRF values.
Attenuation = 46 / 30.48 = 1.509 dB/m
Cable contribution = 1.509 x 0.20 = 0.302 dB
Estimated matched loss = 0.302 + 0.05 + 0.05 = 0.402 dB
Matched power ratio = 10^(-0.402/10) = 0.912, about 91.2%
Verify the finished assembly rather than releasing production from nominal arithmetic. Cable variation, connector behavior, temperature and fixture uncertainty need margin. If the route doubles, the cable contribution approximately doubles in dB at the same frequency.
Avoid these miniature-cable shortcuts
Before release
What are RG178 cable specs?
Reference 83265 is 50 Ω, 1.8 mm coax with PTFE dielectric, FEP jacket and stranded silver-plated copper-clad steel conductor. Its nominal loss and environmental limits remain part-specific.
Is RG196 smaller than RG178?
Not universally. RG196 examples here are 1.71 mm and 2.05 mm, while the RG178 reference is 1.8 mm. Check the exact construction and connector approval.
How much loss does RG178 have at 1 GHz?
The reference lists 46 dB/100 ft, about 1.509 dB/m nominal cable attenuation. A 200 mm length contributes about 0.302 dB before connector effects.
Can micro-coax be used for long antenna feeders?
Only if the actual loss budget permits. Miniature cable loss adds quickly with length; a larger lower-loss cable may be better for a remote antenna.
Do RG178 and RG196 use the same connectors?
Use only connector variants approved for the selected cable dimensions and conductor preparation. Similar diameter does not guarantee the same ferrule, contact or strip instructions.
Can SigmaRF supply miniature RF cable assemblies?
Provide approved cable and interfaces, finished length, route, environment and test limits. SigmaRF can agree the construction and RF verification for the selected build.
RG178 and RG196 solve space problems only when the exact construction and length fit the electrical budget. Neither family is one universal micro-coax specification.
Approve the part, protect the small termination and test the completed assembly. That is how a compact RF route becomes repeatable rather than merely small.
Build an RF assembly around the real requirements
Send the frequency band, connector interfaces, finished length and routing drawing. SigmaRF can match the cable and terminations to your application.