UHF connector
{{Short description|Type of radio frequency connector}}
{{Infobox connector
|name = UHF connector
|type = RF coaxial connector
|image = 250px
|logo =
|caption = PL-259 (male) plug. Outside diameter is about 18 mm.
|designer =
|design_date = 1930s
|manufacturer = Various
|diameter = {{convert|18|mm|in|abbr=on}} (typical)
|width =
|height =
|electrical = Non-constant impedance
{{cite web |title=UHF Connector Series |url=http://www.amphenolrf.com/connectors/uhf.html |website=Amphenol |access-date=23 September 2015 |ref=amphenoluhf}}
|earth =
|maximum_voltage = 500 volts peak
|maximum_current =
|cable = Coaxial
|passband = Typically 0–100 MHz
|physical_connector = SO-239 (socket){{cite patent |country=US |number=2761110 |status=patent |title=Solderless coaxial connector |pubdate=28 August 1956 |fdate=7 December 1953 |pridate=7 December 1953 |invent1=Diambra, Henry M. |assign1=Entron Inc. }}
PL-259 (plug) {{cite patent |country=US |number=4085366 |status=patent |title=Noise reduction device for citizens' band transceivers |pubdate=18 April 1978 |fdate=29 February 1976 |pridate=29 September 1976 |invent1=Padgett, Billy |assign1=Padgett, Billy }}
}}
File:BNC UHF.jpg (background).]]
The UHF connector is a name for a fairly common, but old type of threaded RF connector.{{cite patent |country=US |number=2335041 |status=patent |title=Right-angle electric connector |pubdate=23 November 1943 |fdate=12 August 1942 |pridate=12 August 1942 |inventor=Bruno, William A. |assign=Bruno Patents Inc. }}{{cite patent |country=US |number=2422982 |status=patent |title=Coaxial cable connector |pubdate=24 June 1947 |fdate=7 January 1943 |pridate=7 January 1943 |invent1=Quackenbush, Edward Clarke |assign1=Quackenbush, Edward Clarke }}
The connector design was invented in the 1930s for use in the radio industry.
{{cite book |last=Hallas |first=Joel R. |date=5 October 2012 |title=Care and Feeding of Transmission Lines |publisher=American Radio Relay League |location=Newington, CT |isbn=978-0-8725-9478-4 }} 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" meant frequencies over 30 MHz.{{cite book |last=Henney |first=Keith |year=1941 |title=Radio Engineering Handbook |publisher=McGraw-Hill Book Company |edition=3rd |location=New York, NY |page=514 |section=Section 15 – High frequency transmission and reception |url=http://mirror.thelifeofkenneth.com/lib/electronics_archive/Henney-RadioEngineeringHandbook3rdEd_text.pdf |url-status=dead |access-date=2018-09-12 |df=dmy-all |archive-url=http://web.archive.org/web/20180913073622/http://mirror.thelifeofkenneth.com/lib/electronics_archive/Henney-RadioEngineeringHandbook3rdEd_text.pdf |archive-date=2018-09-13 }}{{cite web |title=Pretty lousy (PL) 259 connectors – the test |date=July 2011 |department=Connectors |website=Hamradio.me |url=http://www.hamradio.me/connectors/pretty-lousy-pl-259-connectors-the-test.html |access-date=16 May 2015 }}{{cite book |title=The Radio Amateur's Handbook |year=1941 |publisher=American Radio Relay League |location=West Hartford, CT |pages=362–363 |edition=18th |chapter=Introduction to UHF |quote=In amateur work, the ultra-high-frequency region is considered to include the {{nobr|56 to 60 MC}} band and all higher frequency bands available for amateur use. |df=dmy-all}} Today, the meaning of the term ultra high frequency (UHF) is instead defined to be frequencies between 300 MHz and 3 GHz{{efn|name=ITU_UHF_note|
Since the latter part of the 20th century, the term "UHF" has been formally defined as the band of frequencies between 300 MHz and 3 GHz, in both the ITU and IEEE official designations for radio bands.{{citation needed|date=January 2025}}
}}
and the frequencies formerly called UHF are now called very high frequency (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.{{citation needed|reason=Proving a negative is hard, but required|date=July 2018}} There is evidence of inconsistency in performance of marketed UHF connectors.{{cite web |title=PL-259 vs. N on 430 MHz |website=IZ2UUF radio amateur technical blog |url=https://www.iz2uuf.net/wp/index.php/2016/01/08/pl-259-vs-n-on-430-mhz/ |access-date=25 May 2020 }} Testing reveals connector designs introduced after WWII, such as N connector and BNC connector, are electrically superior to the 'UHF' connector for modern UHF{{efn|name=ITU_UHF_note}} frequencies. Other testing showed that one sample of UHF connectors had negligible ill effects on signals for frequencies up to 435 MHz.
Other names
The connector reliably carries signals at frequencies up to 100 MHz.
{{cite web |title='UHF' connector test results |department=Connectors |date=October 2011 |df=dmy-all |website=Hamradio.me |url=http://www.hamradio.me/connectors/uhf-connector-test-results.html |access-date=31 January 2012 }} The coupling shell has a {{nobr|{{small|{{sfrac| 5 | 8 }} }} inch}} 24 tpi UNEF standard thread.
The most popular cable plug and corresponding chassis-mount socket carry the old Signal Corps labels PL-259 (plug #259) and SO-239 (socket #239).{{cite book |title = Antenna Equipment RC-292 |date=1966-04-23 |publisher=Department of the Army |id=TM 11-5820-348-15 |df=dmy-all }} These are also known as Navy type 49190 and 49194, respectively.{{cite book |title=Electronic Test Equipment |series=Military Standardization Handbook |volume=I |date=1964-03-11 |publisher=Department of Defense |id=MIL-HDBK 172A |df=dmy-all }}{{efn|
A double-ended SO-239 connector is designated as an SO-238.{{citation needed|date=June 2020}}
}}
PL-259, SO-239, PL-258, and several other related labels used by military services refer to one specific mechanical design, now collectively called UHF connectors, continuing the use of the now-obsolete meaning of 'UHF'.{{efn|name=ITU_UHF_note}}{{efn|
In some countries, for example in Israel, the term PL connector is confusingly associated rather with the analog phone connector.
}}
The designations come from the Joint Electronics Type Designation System, its predecessor, the AN system, and the earlier SCR (Set, Complete, Radio) system.{{cite web |title=Designations Of U.S. Military Electronic and Communications Equipment |website=designation-systems.net |url=http://www.designation-systems.net/usmilav/electronics.html }}
Characteristics
{{Refimprove section|date=April 2018}}
=Mechanical=
By design, all connectors in the UHF connector family mate using the {{nobr|{{small|{{sfrac| 5 | 8 }} }} 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.{{citation needed|reason=I've never seen any definition of the center pin but maybe the mil specs have it somewhere|date=September 2015}} Similar connectors (M connectors) with an incompatible 16 mm diameter, 1 mm metric thread have been produced,{{cite web |title=Drawing of metric connector |website=RF Supplier |url=http://rfsupplier.com/x2/rfbat/tu/728a.jpg |access-date=24 September 2015 |df=dmy-all}} but those are not standard UHF connectors defined by the patent and military specifications.
=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 VHF frequency range.
Despite the name, the UHF{{efn|name=ITU_UHF_note}} connector is rarely used in high performance applications for today's UHF band, as the non-constant surge impedance creates measurable electrical signal reflections above 100 MHz.{{cite patent |country=US |number=2233166 |status=patent |title=Means for transferring high frequency power |pubdate=25 February 1941 |fdate=1 November 1938 |pridate=14 July 1937 |invent1=Hahn, William C. |assign1=General Electric Co. }}{{cite web |title=The UHF type connector under network analysis |department=Chris's amateur radio and electronics resource pages ({{sc|vk3jeg}}) |url=http://www.qsl.net/vk3jeg/pl259tst.html |via=qsl.net |access-date=31 January 2012 |quote=... 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. |df=dmy-all}}
Virtually all of the impedance bump and consequent loss is in the UHF female connector, the SO-239. A typical SO-239 UHF female, properly hooded, has a difference in impedance from the standard 50 Ohm line impedance of about 35 Ohms. The length of the bump is typically {{nobr|{{small|{{sfrac| 1 | 2 }} }} 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 female connectors that maintain a 50 ohm surge impedance.{{cite web |title=A look at the UHF connector |department=UHF connector compensation |series=Technical topics |website={{sc|w0qe}}.com |url=https://www.w0qe.com/Technical_Topics/uhf_connector_compensation.html |access-date=16 September 2018}}
=Power=
Some samples of UHF connectors can handle peak RF power levels well over 1 kilowatt based on the peak voltage rating of 500 V. In practice, some UHF connector products will handle over 4 kV peak voltage.{{cite web |title=Testing coax cable connectors |publisher={{sc|W8JI}} |via=YouTube |url=https://www.youtube.com/watch?v=cbpy7gb9ZbE |url-status=live |archive-url=https://ghostarchive.org/varchive/youtube/20211221/cbpy7gb9ZbE |archive-date=2021-12-21 |ref=w8ji}} {{cbignore}} Manufacturers typically test and warrant UHF jumpers in the 3–5 kV range.{{Citation needed|date=April 2018}} UHF connectors are standard on HF amateur amplifiers rated at {{nobr|1500{{sup|+}} Watt}} output.{{Citation needed|date=April 2018}}
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.{{Citation needed|date=April 2018}} UHF connectors are generally limited by cable heating rather than connector failure.
=Environmental tolerance=
Applications
In many applications, UHF connectors were replaced by later connector designs that have a more nearly uniform surge impedance over the length of the connection, such as the N connector and the BNC connector.{{cite web |title=Lab tests SMA, BNC, TNC, and N connectors |date=August 2011 |department=Connectors |website=Hamradio.me |url=http://www.hamradio.me/connectors/lab-tests-sma-bnc-tnc-and-n-connectors.html |access-date=31 January 2012 }} UHF connectors are still widely used in amateur radio, citizens' band radio, and marine VHF radio applications.{{citation needed|reason=This point needs verification with a reliable source|date=May 2015}}
UHF connectors were also used from the 1950s until the late 1970s on television broadcast and video equipment for composite and component video signals, having been mostly superseded by the late 1970s by BNC connectors on professional and industrial video gear, and by the RCA connector on consumer video hardware.{{citation needed|date=January 2025}}
See also
Notes
{{notelist}}