CS wrote:
What impedance is Navtex aerial cable?? - I think it is probably either
50 or 75 ohm.

I'd guess it is 50 ohms, because that is the default in radio world. TV
is the most common system that uses 75 ohms, almost everything else is
50 ohms.

The coaxial connectors for 50 and 75 ohm cables are different also on
the interconnecting side, so you might not want to plug a 75 ohm
connector to a radio that expects a 50 ohm connector. You can break or
stretch the connector on the radio side, if you use a wrong impedance
connector. As a result, a correct impedance connector might not make a
solid connection anymore.

Tapio