N connector
Encyclopedia
RF connector
A coaxial RF connector is an electrical connector designed to work at radio frequencies in the multi-megahertz range.RF connectors are typically used with coaxial cables and are designed to maintain the shielding that the coaxial design offers. Better models also minimize the change in transmission...
used to join coaxial cables. It was one of the first connectors capable of carrying microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
-frequency signals, and was invented in the 1940s by Paul Neill
Paul Neill
Paul Neill was an electrical engineer at Bell Labs in the 1940s and 1950s. He is credited with helping to invent the BNC, TNC and Type N connectors used for microwave and RF communications....
of Bell Labs
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
, after whom the connector is named.
Design
Originally, the connector was designed to carry signals of up to 1 GHzGHZ
GHZ or GHz may refer to:# Gigahertz .# Greenberger-Horne-Zeilinger state — a quantum entanglement of three particles.# Galactic Habitable Zone — the region of a galaxy that is favorable to the formation of life....
in military applications, but the common Type N today handles up to 11 GHz comfortably. More recent precision enhancements to the design by Julius Botka at Hewlett Packard have scaled this to 18 GHz. The male
Gender of connectors and fasteners
In electrical and mechanical trades and manufacturing, each half of a pair of mating connectors or fasteners is conventionally assigned the designation male or female...
connector is hand-tightened (though versions with a hex nut are also available) and has an air gap between center and outer conductors. The coupling has a 5/8-24 thread
Unified Thread Standard
The Unified Thread Standard defines a standard thread form and series—along with allowances, tolerances, and designations—for screw threads commonly used in the United States and Canada...
. Amphenol suggest tightening to a torque of 15 foot-pounds (20.3 N·m), while Andrew Corporation suggest 20 for their hex nut variant. Since torque limit depends only on thread quality and cleanliness, whereas the main operational requirement is good RF contact without significant steps or gaps, these values should be seen as indicative rather than critical.
Power rating
The peak power rating of an N connector is determined by voltage breakdown/ionisation of the air near the center pin. The average power rating is determined by overheating of the centre contact and is a function of frequency, as heating depends on the resistive insertion loss. Typical makers curves for a new clean connector with a perfect load such as page 275 of for example imply ~5000 watts at 20 MHz and ~500watts at 2 GHz, i.e. a square root frequency derating law as might be expected from skin depth decreasing with frequency. At lower frequencies the same maker recommends an upper bound of ~1000V RMS.To achieve reliable operation in practice over an extended period, a safety factor of 5 or more is not uncommmon, particularly when generic parts may be substituted, or the operating environment is likely to lead to eventual tarnishing of the contacts.
Impedance options
The N connector follows the MIL-C-39012 standard, defined by the US militaryDefense Standard
A United States defense standard, often called a military standard, "MIL-STD", "MIL-SPEC", or "MilSpecs", is used to help achieve standardization objectives by the U.S...
, and comes in 50 and 75 ohm versions. The 50 ohm version is widely used in the infrastructure of land mobile, wireless data, paging and cellular systems. The 75 ohm version is primarily used in the infrastructure of cable television
Cable television
Cable television is a system of providing television programs to consumers via radio frequency signals transmitted to televisions through coaxial cables or digital light pulses through fixed optical fibers located on the subscriber's property, much like the over-the-air method used in traditional...
systems. Connecting these two different types of connectors to each other can lead to damage due to the difference in diameter of the center pin. Unfortunately, many type N connectors are not labeled, and it can be difficult to prevent this situation in a mixed impedance environment. The situation is further complicated by some makers of 75 ohm sockets designing them with enough spring yield to accept the larger 50ohm pin without irreversible damage, while others clearly do not, and expect users to segragate their connectors and adaptors. In general a 50 ohm socket is not damaged by a 75 ohm pin, but the loose fit means the contact quality is not guaranteed.
The 50 ohm type N connector is favored by enthusiasts who create their own Wireless LAN
Wireless LAN
A wireless local area network links two or more devices using some wireless distribution method , and usually providing a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network...
antenna systems, which run at 2.4 GHz or 5 GHz. The Cantenna
Cantenna
A cantenna is a directional waveguide antenna for long-range Wi-Fi used to increase the range of a wireless network.- Origin of the name:...
is one such design. The enthusiasts have settled on using the N connector as a standard connection for homebrew antennas. By using a cable with an N connector one can easily interchange homebrew antennas. 50Ω N connectors are also commonly used on amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
devices (e.g., transceiver
Transceiver
A transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s...
s) operating in UHF bands.