The UHF connector is a name for a threaded

RF connector A coaxial RF connector (radio frequency 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 shieldin ...

. The connector design was invented in the 1930s for use in the radio industry, and is a shielded form of the "

banana plug A banana connector (commonly banana plug for the male, banana socket or banana jack for the female) is a single-wire (one conductor) electrical connector used for joining wires to equipment. The term 4 mm connector is also used, especiall ...

". It is a widely used standard connector for HF transmission lines on full-sized radio equipment, with BNC connectors predominating for smaller, hand-held equipment. The name "UHF" is a source of confusion, since the name of the connectors did not change when the frequency ranges were renamed. The design was named during an era when "

UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...

" meant frequencies over 30

MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...

. Today,

Ultra high frequency Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter ...

(UHF) instead refers to frequencies between 300 MHz and 3 GHz"UHF" is 300 MHz and 3 GHz in both the ITU and IEEE

radio band The radio spectrum is the part of the electromagnetic spectrum with frequencies from 0 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particular ...

designation systems and the range of frequencies formerly known as UHF is now called "

VHF Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF ...

". Unlike modern connector designs that replaced it, no active specification or standard exists to govern the mechanical and electrical characteristics of the so-called "UHF" connector system making it effectively a deprecated design with no guarantee for suitability to an electrical or mechanical purpose.. Evidence of inconsistency exists. Testing reveals post WWII connectors designs, such as

N connector The N connector (also, type-N connector) is a threaded, weatherproof, medium-size RF connector used to join coaxial cables. It was one of the first connectors capable of carrying microwave-frequency signals, and was invented in the 1940s by Pau ...

and

BNC connector The BNC connector (initialism of "Bayonet Neill–Concelman") is a miniature quick connect/disconnect radio frequency connector used for coaxial cable. It is designed to maintain the same characteristic impedance of the cable, with 50 ohm and 7 ...

are electrically superior to the 'UHF' connector for modern UHF frequencies. Other testing reveals one UHF connector sample shows negligible effect on frequencies up to 435 MHz.

Other names

The connector reliably carries signals at frequencies up to 100 MHz. The coupling shell has a inch 24 tpi UNEF standard thread. The most popular cable plug and corresponding chassis-mount socket carry the old Signal Corps nomenclatures PL-259 (plug) and SO-239 (socket). These are also known as Navy type 49190 and 49194 respectively. A double-ended SO-239 connector is designated as an SO-238. PL-259, SO-239, PL-258, and several other related military references refer to one specific mechanical design collectively known as the UHF Connector. In some countries, for example in

Israel Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...

, the term 'PL connector' is confusingly associated rather with the analog phone connector. The designations come from the

Joint Electronics Type Designation System The Joint Electronics Type Designation System (JETDS), which was previously known as the Joint Army-Navy Nomenclature System (AN System. JAN) and the Joint Communications-Electronics Nomenclature System, is a method developed by the U.S. War Depa ...

, its predecessor AN system, and the earlier SCR (Set, Complete, Radio) system.

Characteristics

Mechanical

By design, all connectors in the UHF connector family mate using the inch 24 tpi threaded shell for the shield connection and an approximately 0.156 inch-diameter (4 mm) pin and socket for the inner conductor. Similar connectors (M connectors) with an incompatible 16 mm diameter, 1 mm metric thread have been produced, but these are not standard UHF connectors by definition.

Surge impedance

UHF connectors have a non-constant surge impedance. For this reason, UHF connectors are generally usable through HF and the lower portion of what is now known as the

frequency range. Despite the name, the UHF connector is rarely used in commercial applications for today's

frequencies, as the non-constant surge impedance creates measurable electrical signal reflections above 100 MHz. Virtually all of the impedance bump and loss is in the UHF female. A typical SO-239 UHF female, properly hooded, has an impedance bump of about 35 ohms. The length of the bump is typically inch, where the female pin flares to fit over the male pin. This bump can be mitigated by using a honeycomb dielectric in the female pin area. Many VHF/UHF amateur operators use special UHF females that maintain a 50 ohm surge impedance.

Power

Some samples of UHF connectors can handle RF peak power levels well over one

kilowatt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...

based on the voltage rating of 500 Volts peak. In practice, some UHF connector products will handle over 4 kV peak voltage. Manufacturers typically test UHF jumpers in the 3-5 kV range. UHF connectors are standard on HF amateur amplifiers rated at 1500⁺ Watts output. In practice, voltage limit is set by the air gap between center and shield. The center pin diameter and contact area is large enough that pin heating is not an issue. UHF connectors are generally limited by cable heating rather than connector failure.

Environmental tolerance

The UHF connector is not weatherproof.

Applications

In many applications, UHF connectors were replaced by designs that have a more uniform surge impedance over the length of the connector, such as the

and the

. UHF connectors are still widely used in

amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency commu ...

Citizens Band radio Citizens band radio (also known as CB radio), used in many countries, is a land mobile radio system, a system allowing short-distance person-to-many persons bidirectional voice communication among individuals, using two way radios operating on ...

, and marine VHF radio applications.

Notes

References

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