Roy Lewallen wrote:
Jeroen Belleman wrote:
It's one of my long-time gripes about coaxial connectors that N
and BNC series of the two impedance levels are sufficiently
compatible to mate together, but not enough to do so without
damage. In a lab with someone ignorant of this fact, it's a
source of endless trouble.
All the 75 ohm BNC connectors I have, have the same diameter
center pin in the connection region as 50 ohm connectors. The
difference is in the thickness of the dielectric around the pin
in the connection region, being much thinner in the 75 ohm
connectors. The pin of the 75 ohm connector is smaller only where
it's in solid dielectric at the bottom of the connector.
Roy Lewallen, W7EL
Hi Roy,
There's lots of room for confusion. The Kings tool FAQ implies the
center contact diameter got smaller when the pin was redesigned and
the old crimp die set would not work:
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Why won't my Kings 2025-X-9 die set work with the 2065-X-9
connectors?
With the redesign of the True 75 Ohm BNC connectors, the center
contact diameter got smaller to maintain a constant 75 Ohm
impedance through the connector. Consequently, the center contact
crimp dimension got smaller also.
The problem with the inability of the die set to crimp this new
connector is probably because it is the older, larger die
dimension. The Kings website has a Cross-Reference Search that
lists the applicable die set for most Kings connector part
numbers.
http://www.kingselectronics.com/Reso...4/Default.aspx
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However, another manufacturer claims their new 75 ohm hardware is
interchangeable with 50 ohm connectors:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~
TRUE 75 Ohm BNC & Connectors
Where Controlled Impedance is a Necessity
Emerson Network Power Connectivity Solutions is introducing its
premium line of TRUE 75 Ohm BNC connectors and adapters. These
flexible cable 3 Piece BNC Connectors are essential for analog and
digital high frequency signals.
They have been designed around MIL-STD-202 for up to a 3GHz
frequency range, and are constructed of high performance materials
including a machined nickel plated over brass housing, a teflon
dielectric and gold plated brass contacts. These connectors are
designed to eliminate distortion and impedance mismatching caused
by using 50 ohm connectors on 75 ohm cables, and they safely
inter-mate with standard 50 Ohm BNC connectors.
http://emersonnetworkpower.com/webap.../pdfs/True-75-
Ohm.pdf
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If your junkbox is anything like mine, it may have stuff purchased
20 years ago mixed with more recent purchases. So it might be
worthwhile to check carefully before mating different hardware.
Regards,
Mike Monett