UHF connector

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UHF connector
PL-259 (male) plug. Outside diameter is about 18 mm.
Type RF coaxial connector
Designer E. Clarke Quackenbush[1]
Designed 1930s
Manufacturer Various
Diameter 18 mm (0.71 in) (typical)
Cable Coaxial
Passband Typically 0-100 MHz
Connector SO-238 (socket)
PL-259 (plug)
"Classic" UHF connector with a soldered center pin. The fringe of braided shielding at the rear has not been fully trimmed away.
Adaptor from SO-238 to BNC connector

The UHF connector[2] is a pre-World War II threaded RF connector design, from an era when "UHF" referred to frequencies over 30 MHz.[3][4] Originally intended for use as a video connector in radar applications, the connector was later used for other RF applications.[citation needed] This connector was developed on basis of a shielded banana plug.[citation needed]

UHF connectors are generally usable through what is now known as the HF and the lower VHF frequencies[5] and can handle RF power levels over one kilowatt.[citation needed] There is variation between manufacturers with the choice of dielectric, the PTFE types being favored where low loss is desired.[citation needed] The average power handling of the PTFE versions is essentially set by heating of the center pin, and is therefore frequency-dependent, as the RF resistance rises as the skin depth falls.[citation needed] At low frequencies, the power handling is rather better than that of the similar-sized N connector.[citation needed] The UHF connector is the most common connector in amateur radio applications up to 150 MHz.[citation needed] In the US, the silver-plated version with Teflon dielectric is used in UHF applications up to 450 MHz for the 70 cm band.[citation needed]

Despite the name, the UHF connector is rarely used in commercial applications for UHF frequencies, as the non-constant impedance (the impedance drops to 30-40 Ω for about a centimeter in the central region of the connector) means they create significant electrical signal reflections above 150 MHz.[5][6][7]

The most popular cable plug and corresponding chassis-mount socket carry the old Signal Corps nomenclatures PL-259 (plug) and SO-238 (socket). The PL-259 can be used with large diameter coaxial cable, such as RG-8/U and RG-9/U, and the smaller diameter RG-58/U and RG-59/U with the use of UG-175/U and UG-176/U adapter sleeves. "PL-259" refers to one specific mechanical design, but the term is often used for any compatible UHF cable plug. The thread is 58 inch 24tpi UNEF standard.[citation needed] Other UHF connectors with a similar—but incompatible—metric thread have been produced.[citation needed] The center conductor jack on the SO-238 will also accept a 4 mm banana plug.[citation needed]

In many applications, UHF connectors were replaced by designs that have a more uniform impedance over the length of the connector, such as the N connector and the BNC connector,[8] but they are still widely used in amateur radio, citizens' band radio, and marine VHF radio where mechanical robustness and ease of use are more important than a small mismatch.[citation needed] The "classic" PL-259 connector is resistant to damage even if stepped on accidentally.[citation needed]

One reason for the popularity of the UHF connector is its ease of assembly.[citation needed] While crimp connectors exist, the solderable screw-on connector is more common because no expensive specialized crimping tools are required.[citation needed] The connector is not suitable for outdoor applications by itself, but can be made weather resistant by wrapping it with self-adhesive silicone C-Tape.[citation needed]

UHF connectors were also used for the input and output of composite video signals for older video equipment (such as VTRs and monitors) dating from the late 1970s and earlier.[citation needed] They were known by BBC engineers as "F & E" connectors, after Films & Equipment, a manufacturer.[citation needed]

See also[edit]


  1. ^ UHF RF Connector Specifications and Interface Dimensions | Amphenol RF
  2. ^ Historical details on Amphenol site 
  3. ^ "(PL) 259 Connectors". Connectors. Hamradio.me. July 2011. Retrieved 16 May 2015. 
  4. ^ "Introduction to U.H.F.". The Radio Amateur's Handbook (18th ed.). West Hartford, CT: American Radio Relay League. 1941. pp. 362–363. In Amateur work, the ultra-high-frequency region is considered to include the 56 to 60 Mc band and all higher frequency bands available for amateur use. 
  5. ^ a b "‘UHF’ Connector Test Results". Connectors. Hamradio.me. October 2011. Retrieved 31 January 2012. 
  6. ^ "The UHF type connector under network analysis". Chris's Amateur Radio and Electronics resource pages. Retrieved 31 January 2012. [. . .] at 432 MHz [. . .] we see a loss in the order of 1.0 dB, this equates to a transmission loss of around 6 Watts with 25 Watts input. 
  7. ^ Amphenol RF - UHF connector Series, retrieved 2010-08-05 
  8. ^ "Lab Tests: SMA, BNC, TNC and N Connectors". Connectors. Hamradio.me. August 2011. Retrieved 31 January 2012. 

External links[edit]