SMA Male Vs. Female: An ultimate guide on SMA connectors

About SMA Male Vs. Female, Many coaxial electronic connectors work at RF or radio frequencies. One of the most commonly used RF-type connectors is SMA, which is especially in significant demand in the complex applications of the medical industry due to their sturdiness, reliable performance, and ease of installation in electrical systems.

SMA connector basics:

SMA stands for sub-miniature A connectors used in different RF assemblies requiring coaxial connections.

With SMA connectors, you can establish connectivity among boards and microwave machinery, including attenuators, filters, oscillators, and mixers.

SMA connector performance:

SMA connectors can maintain a constant impedance of 50 ohms across the SMA connectors.

They could work for operations requiring up to 18 GHz. Some versions can work for higher frequencies up to 12.4 GHz, and others for higher up to 24-26.5 Gigahertz.

The higher frequencies had to function with a higher return loss.

SMA connectors have a reflection coefficient of up to 24 Gigahertz, which is higher than the other connectors due to their difficulty in anchoring dielectric support accurately.

However, despite this problem, some manufacturers introduced connectors that can operate at frequencies up to 26.5 GHz.

In flexible cables, the cables determine the frequency limit and not the connectors because, compared to the cables, the loss of SMA connectors is much higher, especially for frequencies that need to be used. 

SMA connector power rating:

The power handling capacity of mated coaxial SMA connectors is crucial for some applications, determined by the ability to allow the flow of the high current and moderate the temperature in heat-rise instances.

The heating effect in the SMA connectors arises from the contact resistance from the contact surface area and the mated contacts.

So, you must ensure that central contacts mate together correctly.

Also, you must understand that average power ratings get affected with the rise in frequency, as resistive loss increases as frequency increases.

Depending on the manufacturer, there are variable figures for the power handling of these connectors.

However, some common ones indicate they can handle 500 wattage power at 1 GHz, while others may handle only 200 watts at 10 Gigahertz.

SMA connector mechanical details:

As a standard for all connectors, gender is assigned to the innermost component of the connector.

  • The SMA Male connector has a threaded barrel with 36 threads per inch and ¼ inch diameter. 
  • The hexagonal nut of the male version measures around 0.3125 inches/5/16 inches, or 8mm, across two opposite flats. Based on this, you can use a wrench for the #6 SAE hex nut. It will cover the outer mating connection of the male connector that comes in contact with the female outer. As a result, the inner diameter of the outer conductor remains the same across the connector. 
  • The male SMA connector has a center pin that mates with the female sleeve for the central connection.
  • The dielectric, made of PTFE, supports the central pins.
  • On the other hand, outer threads on the female connector’s barrel mate with the male connector’s hexagonal nut.
  • The Polytetrafluorethylene center of the two mating halves makes contact and preserves the impedance of the connector.

SMA connector cons:

The only disadvantage of the connector is the limited connect-disconnect cycles.

However, that was not a problem for semi-rigid coax cables as more or less these installations were fixed after initial assembly.

Industries developed full connectors with center pins when the flexible cables started using SMA connectors, which had many connect-disconnect cycles and were manufactured to meet high standards.

The rating of the SMA connectors is usually up to 500 cycles, but you need to properly torque the SMA connector during connection to achieve this target.

For brass and stainless steel connectors, you will need a 5/16-inch torque wrench, set to 3-5 in. lbs and 7-10 in.lbs.

Sometimes, the flat portions are also available on the cable aside from the assembly to allow proper torquing.

In such cases, you can use another wrench to prevent it from rotating so the cable joint is not damaged.

If you want to improve the life and performance of the connectors, maintain surface cleanliness.

The connector’s surface accumulates dust and dirt, affecting their work.

Also, look for loose debris on the internal surface and clean it with the help of compressed air before mating.

This step is especially essential for vector network analysis systems.

SMA connectors reverse polarity:

A variation of SMA connectors is RP-SMA or reverse polarity SMA. It is named so as it reverses the interface gender.

The reverse polarity has no connection with the signal polarity; it only means the gender of the connector’s contact pin.

The external housing is the same as conventional female SMA in female RP-SMA, but there is a male pin instead of a central receptacle.

Similarly, in the male version of RP-SMA, the connector has threads inside the barrel, but there is a central receptacle instead of a male pin.

Due to this reason, SMA and RP-SMA are incompatible with each other.

SMA male vs. female: Comparison chart

SMA MaleSMA female
Standard polarityThe outer configuration of the reverse polarity is the same as that of the standard one, but it has a female sleeve and not a male pin. The different diameters areOuter: 6.35 mmInner 4.59 mmPin Insert: 1.30 mmThe SMA female has outer ¼-inch-36 threads. There is a female sleeve in the standard polarity connector. The different diameters are:
Outer: 5.49 mmInner: 4.60 mmPin insert:1.30mm
Reverse polarityHere, the female version has a male pin instead of a female sleeve. The different diameters are:Outer: 5.49 mmInner 4.60 mmPin 0.97 mmPin Tip: 0.38 mm.The outer configuration of the reverse polarity is the same as that of the standard one, but it has a female sleeve and not a male pin. The different diameters are outer: 6.35 mmInner 4.59 mmPin Insert: 1.30 mm
SMA coax cable assemblies

SMA coax cable assemblies

Designing the perfect SMA RF connector:

RF SMA connectors are either a single connector to an existing system or a custom cable assembly with multiple SMA connectors and adapters to serve a higher range of applications. 

Helping maintain the impedance and thus is a popular choice, most SMA RF connectors have a right-angle design nowadays, but others also have a straight-angle design depending on the circuit. 

While designing the connectors, manufacturers need to be attentive in calculating the structural components and dimensions of the connection very precisely.

Further, the assembly of the connectors should be flawless.

Also, one must give special care and attention to the soldering, as too much can lead to impedance mismatch.

Further, wrong dimensions, mechanical failures, or excess air around the contacts can also result in an impedance mismatch.

Different ways to mount SMA connectors:

  • Panel mount: this female is suitable for harsh conditions similar to that in the military and industries. Panel mounts have 2-hole and 4-hole configurations, making them ideal for wireless infrastructure and instrumentation. 
  • Bulkhead mount: this is again a female mount having a thread length longer than 4.3 mm (standard) to allow easy attachment with the panel or wall using a nut or washer.
  • Through-hole mount: it is either vertical or 90 degrees. You can find them in non-magnetic options in the medical field.
  • Edge mount: a vertical mount found in drop-in and standard varieties.
Edge mount SMA

Edge mount SMA

Does UL certification matter with SMA RF connectors?

SMA RF connectors are used in life and death conditions, and one should not take any risk with the quality and precision while manufacturing.

Even the smallest of errors can lead to catastrophic situations. Thus, SMA RF connectors must use UL-certified components. 

These components come to the market after being tested and verified for durability, functionality, and structural integrity.

In this way, designers can use components with specific operating ranges.


The screw-type SMA connectors give them mechanical sturdiness, durability, and long-lasting performance, which is important for Rf devices.

At Cloom, we manufacture thousands of rf cables with SMA connectors for different equipment.

We use connectors that meet the stringent quality assurance and quality control standards of the Underwriters Laboratories (UL).

For more information, you can contact our experts, who can guide you to get the best products based on your specific requirements. 

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