 PL-259 (male) plug. Outside diameter is about 18 mm. | |||
| Type | RF coaxial connector | ||
|---|---|---|---|
| Production history | |||
| Designed | 1930s | ||
| Manufacturer | Various | ||
| General specifications | |||
| Diameter | 18 mm (0.71 in)(typical) | ||
| Cable | Coaxial | ||
| Passband | Typically 0–100 MHz[1] | ||
| Connector | SO-239 (socket)[2] PL-259 (plug)[3] | ||
| Electrical | |||
| Signal | Non-constant impedance[4] | ||
| Max. voltage | 500 volts peak[4] | ||
TheUHF connector[4] is a name for a fairly common, but old type of threadedRF connector.[5][6]The connector design was invented in the 1930s for use in the radio industry.[7][4] It is a widely used standard connector forHF transmission lines on full-sized radio equipment, withBNC connectors predominating for smaller, hand-held equipment.[7]
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.[8][9][10] Today, the meaning of the termultra high frequency (UHF) is instead defined to be frequencies between 300 MHz and 3 GHz[a]and the frequencies formerly called UHF are now calledvery 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] There is evidence of inconsistency in performance of marketed UHF connectors.[7][1][11] Testing reveals connector designs introduced after WWII, such asN connector andBNC connector, are electrically superior to the 'UHF' connector for modern UHF[a] frequencies.[7][1] Other testing showed that one sample of UHF connectors had negligible ill effects on signals for frequencies up to 435 MHz.[11]
The connector reliably carries signals at frequencies up to 100 MHz.[1] The coupling shell has a 5 / 8 inch 24 tpi UNEF standard thread.[4]The most popular cable plug and corresponding chassis-mount socket carry the oldSignal Corps labelsPL-259 (plug #259) andSO-239 (socket #239).[12] These are also known asNavy type 49190 and49194, respectively.[13][b]
PL-259,SO-239,PL-258, and several other related labels used by military services refer to one specific mechanical design, now collectively calledUHF connectors, continuing the use of the now-obsolete meaning of 'UHF'.[a][4][c]The designations come from theJoint Electronics Type Designation System, its predecessor, the AN system, and the earlier SCR (Set, Complete, Radio) system.[14]
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By design, all connectors in the UHF connector family mate using the 5 / 8 inch 24 tpi threaded shell for the shield connection[4] and an approximately 0.156 inch-diameter (4 mm) pin and socket for the inner conductor.[citation needed] Similar connectors (M connectors) with an incompatible 16 mm diameter, 1 mm metric thread have been produced,[15] but those are not standard UHF connectors defined by the patent and military specifications.[4]
UHF connectors have a non-constantsurge impedance.[4] For this reason, UHF connectors are generally usable throughHF and the lower portion of what is now known as theVHF frequency range.[1]Despite the name, the UHF[a] connector is rarely used in high performance applications for today'sUHF band, as the non-constant surge impedance creates measurable electrical signal reflections above 100 MHz.[1][16][17]
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 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.[18]
Some samples of UHF connectors can handle peak RF power levels well over 1 kilowatt based on the peak voltage rating of 500 V.[4] In practice, some UHF connector products will handle over 4 kV peak voltage.[19] Manufacturers typically test and warrant UHF jumpers in the 3–5 kV range.[citation needed] UHF connectors are standard on HF amateur amplifiers rated at1500+ Watt output.[citation needed]
In practice, voltage limit is set by the air gap between center and shield.[7] The center pin diameter and contact area is large enough that pin heating is not an issue.[citation needed] UHF connectors are generally limited by cable heating rather than connector failure.[7]
The UHF connector is not weatherproof.[4][7]
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 theN connector and theBNC connector.[20] UHF connectors are still widely used inamateur radio,citizens' band radio, andmarine VHF radio applications.[citation needed]
UHF connectors were also used from the 1950s until the late 1970s on television broadcast and video equipment forcomposite andcomponent video signals, having been mostly superseded by the late 1970s byBNC connectors on professional and industrial video gear, and by theRCA connector on consumer video hardware.[citation needed]
In amateur work, the ultra-high-frequency region is considered to include the56 to 60MC band and all higher frequency bands available for amateur use.
... 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.
