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U.FL Cables Coax Types Compared: 1.13mm, 1.32mm, 1.37mm, RG174, RG178

George Hardesty
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U.FL Cable Coax Comparison

Comparison of Coaxial Cable Types 1.13mm, 1.32mm, 1.37mm, RG174 for for U.FL Cable Assemblies

1.13mm coaxial cable is the most commonly-used coax for U.FL cables - especially short cables. 1.13 is the only coax that can be used with MHF4 cables.

1.13mm Coaxial CableWhen connecting U.FL connector to a jack on a mini-PCI card or board, sometimes the tight space requires the use of 1.13mm cable, because it is very thin and flexible: It is not always necessary to use 1.13mm cable, but on occasion it is necessary to use 1.13mm cable, to prevent the U.FL connector from popping off the U.FL jack (sometimes in tight spaces, RG174 and RG178 cause the U.FL connector to pop off).

1.13mm cable has a 50 Ohm resistance (+/- 3Ohm) and is a single shielded coaxial cable with a FEP jacket.

Operating temperature range of 1.13mm coax: -55°C - +180 °C

Differences with RG174 include:

  • Overall smaller diameter of 1.13mm (0.04 inches), an AWG of 32.
  • A smaller diameter (0.26mm – 0.01 inches) silver plated annealed copper core and non-polymer dielectric.
  • Low loss 1.13 coax variants also have an insulating binder made from copper polyester tape which enhances shielding.
  • 1.13 coax achieves a lower conductor resistance (482Ohm/km) than RG178 and similar insulation resistance (3000 Ohm/km).
  • Its VSWR is 1.3 between 0 and 6 GHz up to a maximum of 1.45 between 6 and 8GHz. Optimal frequency is 6GHz.

1.32mm coaxial cable has 50 Ohm resistance (+/- 3Ohm). It is single shielded with a silver covered copper braid and has an FEP jacket. Key differences with RG174 include: Lower diameter – the dielectric diameter is 0.70 mm (0.028 inches). The AWG of the cable is 32 A conductor diameter 0.22mm. The core is silver plated solid copper. Coverage of the braided shielding may be lower at 90%. A double shielded variant of 1.32mm coaxial cable has two layers of silver coated copper braid with the additional layer having coverage of 78%. Conductor resistance is slightly higher at 850Ohm/km and insulation resistance is lower than that of RG178 at 1000Ohm/km. VSWR is equivalent at 1.3 between 0 and 6 GHz. Optimal frequency is 6 GHz.

1.37mm coax: Best Choice for Low Loss: 1.37mm mini coaxial cable has similar signal loss as RG174 and RG178, but is thinner and more flexible: It has same size conductor as RG178 cable, but smaller overall diameter. It's flexibility helps the U.FL cable connectors stay attached, and makes it more suitable than RG174 or RG178 for the tight space of a small case or enclosure. See attenuation table and specs of 1.37mm mini coax cable.

RG174 (also known as ‘mini-coax’ or ‘micro-coax’)

RG174 cable has a 50 Ohm resistance (+/- 2Ohm) and single shielding with tinned copper braid but differs in the following ways:

  • Its non-polar polymer dielectric is typically made from polyethylene (PE) and has almost double the amount of insulation present by diameter.
  • Its central conductor can be stranded with up to 7 strands of copper clad steel and is of greater diameter (0.48mm vs 0.31mm for RG178)
  • Depending on the manufacturer, the jacket is made from PVC.
  • Overall diameter is greater than RG178 at 2.79mm (0.11 inches) and AWG is lower at 26.
  • RG174 has a much lower conductor resistance (142Ohm/km) and higher insulation resistance (1000Ohm/km). Optimum frequency is 2.4Hz.
Freq. (MHZ) RG178 RG174 1.13 1.32 (SGL Shield) 1.32 (DBL Shield)
900 0.408 0.300 0.71 0.71 0.71
2000 0.630 0.86 1.00 0.85
2500 0.784 0.740 0.98 0.96
3000 0.820 1.06 1.21 1.21
5000 1.38 1.54 1.55 1.48
6000 1.50 1.65 1.70 1.59

See list of all of our articles about U.FL cables and connectors.

1.13 coaxial cable with a U.FL female right-angle connector

RG 178 Applications

RG 178 is a thin cable with good thermal resistance (operating temperature range from -55 to 200 degrees Celsius or -67 to 392 degrees Fahrenheit). It is typically used for high frequency transmissions. This coax cable has a variety of commercial uses including:

  • Testing and measurement
  • Internal cabling
  • Television and CCTV
  • Telecommunications and broadband
  • Wireless communication infrastructure

Structure and Material Composition of RG178 Coaxial Cable

RG 178 has an American Width Gauge (AWG) of 30 and an overall diameter of 1.83millimeters (0.071 inches). The bend radius of this cable is usually between 7.5mm (0.29 inches) and 9.0mm (0.35 inches). RG 178 cable’s structure is typical of coaxial cable comprising:

  • A central conductor made of silver coated, copper clad steel with a diameter of 0.3 millimeters (0.01 inches).
  • Insulation material to surround the conducting core of 0.86 millimeters (0.03 inches), known as a dielectric, made from Polytetrafluoroethylene (PTFE).
  • A single metallic shielding layer – made from woven or braided silver coated copper. The shield coverage is typically 95% and influences the transmitting performance of the cable.
  • An external plastic jacket made from Fluorinated ethylene propylene (FEP) which may be opaque or transparent.

Electrical Characteristics of RG178 Coaxial Cable

RG178 has a relatively tightly matched impedance of 50 Ohm with a range of (+/- 2 Ohm) and VSWR of up to 1.3 between 0 and 6 GHz. The conductor resistance of this cable is typically around 800 Ohm/km and the dielectric resistance is 3000 Ohm/km. Optimum frequency range for this cable is between 2.5 GHz and 3 GHz.

RG178 Shielded Low-Loss Coax for U.FL Cables

RG in RG178 stands for Radio Guide and is a designation given to a range of coaxial cables which were originally developed during the World War II era for military purposes. The RG number specifies the gauge, or thickness of the cable. Higher RG numbers are typically associated with a thinner central conductor in the coax cable. Overall greater diameters are due mainly to the insulating layers of the cable and provide lower attenuation of signal over longer lengths of cable.

Wireless IoT technologies compatible with U.FL cables

It is important to note that the electrical and radio frequency characteristics of a specific coaxial cable may vary in performance from manufacturer to manufacturer. Exact performance and suitability for applications can be discerned from individual manufacturer specifications. Most RG 178 coax will also conform to the standards of MIL-C-17F or some other US military connector specification.

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