[Elecraft] BNC & SO 239

[Ron D'Eau Claire]

An SO-239 is the socket that goes with the PL-239 plug. They are often
called "UHF Connectors" because they were often used in that service
many years ago although they are not especially good above HF. The "239"
series of connectors were developed in the 1930's for Amphenol for use
with the coaxial lines that were coming into commercial use. They do not
present a "constant impedance" and so reflections on the transmission
line (high SWR) becomes an issue as the frequency goes up. For Ham use
they are generally okay up through 2 meters.  

Early coaxial lines were quite lossy compared to what we have today, and
larger sizes of coax such as RG-8 were used at 2 and 1-1/4 meters by
hams to minimize those losses. BNC connectors are not suitable for use
with the larger coaxial lines. I suspect that's what perpetuated the use
of the larger 239 style connectors at UHF in spite of their higher
losses. 

The BNC was a standardized connector system developed in WWII as better,
lower loss, connectors were needed for higher frequencies. "BNC" stands
for Bayonet (the type of locking mechanism)- Neil-Councelman (the
inventors). Neil and Councelman did the design work that reduced
reflections and made these connectors superior up through UHF
frequencies. They also invented the variation used to produce more
secure connections in aircraft called the "Type N", which is a BNC sized
connector with a screw on collar around it to secure it better. 

So, in theory, the BNC is a superior connector electrically, although
there is little or no practical difference at HF. The BNC is smaller and
readily-available. I suspect that's why they become popular on smaller
rigs. 

That BNC/SO-239 adapter you have is also excellent for connecting your
K2 to a wire antenna if you have the KAT2 ATU installed. A banana plug
will fit snugly inside the center hole of the SO-239, eliminating the
need to buy another adaptor for that use.

Ron AC7AC
K2 # 1289

-----Original Message-----
i have an adapter for my k2 antenna to go from the bnc to a so 259 or
239 whatever will that work or is it for vhf?  i cant tell the
difference between s0259 and pl 259 or it was something like that at rat
shack.  what im trying to do is hook up the k2 to regular coax cables,
never had a radio with a bnc connector other than my scanner ht.

john wt5y