Help with HP 4951B protocol analyzer + 18179A

Tony Duell ard at p850ug1.demon.co.uk
Fri Feb 17 18:03:26 CST 2006


> Hi
>  I've made a couple of these from cable, both starting from
> RCA on both ends and BNC on both ends. Get the connector

Don't forget there are 2 types of BNC connector, 50 Ohm and 75 Ohm. I am 
told the centre pin diameter is different between them, and using the 
wrong oen can cause intermittant connections or damage to the socket.

For video applications, you need a 75 Ohm plug. Almost all other 
appications (test equipment, ethernet) use 50 Ohm.

> you need from RS or other supply and make the cable. It
> only takes a few minutes and doesn't require special
> skills, other than using a soldering iron.

At one time the Maplin cataloge contained instructions for fitting a BNC 
plug. They were hilarious!. They told you to remove xx.xx mm of 
insulation from the cable (yes, to the nearest 1/100th of a millimetre). 
Clearly an imperial dimension that had been converted by somebody who 
didn't think about it.

In fact the BNC plug is very easy to wire. Probided you remove enough 
outer insulation from the cable (1" is plenty), every subsequent cut is 
against a part of the plug you've fitted (trim the braid around the 
outside of the metal ferule, the inner isulation against the end of the 
ferule, the inner conductor against the end of the flat insulator, etc).

-tony




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