On 19/08/2017 09:32, Ian Jackson wrote:

Sheffield & District Wireless Society

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Foundation Course Material in PDF Format

Posted: 18 Aug 2017 04:04 AM PDT
http://sheffieldwireless.org/2017/08...in-pdf-format/

PDF File versions for the Foundation Course

Please may I offer one correction:

In 'Antennas & Feeders', the information about BNC connectors, you are
warned "Take care not to mix incompatible 50 and 75 Ohm versions which have
different inner pin sizes".

This is NOT totally correct. While the profile of the pins are slightly
different (the 50 ohm usually has a somewhat stubbier point), the
diameters are the same. The difference in characteristic impedance is
achieved by the amount of PTFE dielectric.

As a result, you CAN physically mate 50 and 75 ohm BNC connectors (both
sexes).

This is far too technical for a 'training scheme' that produces Fulls
who have to ask the question "USB/LSB? I'm confused!".


--
Spike