UHF connector, including the PL259 plug, and SO239 socket
- details and information about the UHF RF connector, including the SO239
UHF socket and PL259 plug, UHF connector adapters and links to suppliers.
The UHF connector is a coaxial RF connector that is used in
low cost applications for frequencies often in the HF and the bottom end of the
VHF spectrum. Although it does not offer a particularly high level of
performance, this RF connector is nevertheless satisfactory for many
applications where cost may be an issue.
The UHF RF connector was designed in the 1930s by E. Clark
Quackenbush, a design engineer working for the Amphenol company. This RF
connector design was aimed to cover frequencies in the range 0.6 to 300 MHz and
it was aimed at use within the radio industry. In view of the fact that the
frequency of operation for the connector extended to 300MHz - the bottom of the
UHF band of frequencies, it was given the name of UHF connector.
Connector designations
In view of the fact that the UHF connector was designed in
the Amphenol company, it is also sometimes referred to as the Amphenol
connector. In addition to this the plugs and sockets may be referred to by
different designations. The plug may be referred to as a PL259 coaxial
connector, and the socket as an SO239 connector. These numbers arise from the
original military numbers given to the UHF connectors
Basic description
These coaxial connectors have a threaded coupling, and this
prevents them from being removed accidentally. It also enables them to be
tightened sufficiently to enable a good low resistance connection to be made
between the two halves.
The basic RF connector (PL259) is has a relatively large
threaded hole through which the coax cable enters. This is suitable for large,
low loss cable, and also make the connector suitable for relatively high power
applications. However where smaller cable is to be used, versions with a thinner
hole are available or a reducer sleeve can be used. This reducer sleeve screws
into the threaded coax cable entry hole may be used to make the cable entry
diameter suite the size of the cable being used.
Limitations
The drawback of the UHF or Amphenol connector is that it has
a non-constant impedance. This limits their use to frequencies of up to 300 MHz,
but despite this these UHF connectors provide a low cost RF connector suitable
for many applications, provided that the frequencies do not rise. Also very low
cost versions are available for applications such as CB operation, and these are
not suitable for operation much above 30 MHz. In view of their non-constant
impedance, these RF connectors, of any quality, are now rarely used for many
professional applications, being generally limited to CB, amateur radio and some
video and public address systems.
Soldering PL259 connectors
Soldering PL259 connectors is not always easy. Start by
stripping back about 1.5 inches (35mm) of the outer coating or sheath of the
cable, taking care not to cut too deeply and score any of the fibres of the
conductive braid. Leave around 0.5 inch (13mm) of the copper braid or shielding
in place and then remove about 0.5 inch (13mm) of the plastic core.
Tin the exposed central copper core. To do this, heat the
core with the soldering iron and apply a thin even coating of solder to it. Take
care not to keep the soldering iron on the conductor for too long otherwise the
dielectric spacing between the outer and inner conductors of the coax will melt.
Once the cable has cooled slide the inner part of the PL259 plug over the cable
with a screwing action until the copper core appears at the end of the centre
pin. The trimmed shield will have become trapped between the core and the inside
of the PL259. The outer sheath or covering or covering of the coax cable will
ensure a snug fit and any protruding shielding should be removed with the sharp
knife.
Summary
The UHF connector has been available for many years, and it
is likely to remain in use for many years to come. These days it is not normally
used in many professional applications as other connector types are generally
more suitable. Nevertheless the UHF connector is still used in some more niche
applications where the highest performance is not required, and where its rugged
mechanical construction and low cost are important.
|
