Impedances and transmission line effects...

[Diabolical Artificer]

Thanks for the explanations and clarification. Its a bit confusing because AFAIK it's a cables capacitance not its resistance that matters with VHF signals. As AF has low ish reactance I guess it doesn't matter that my test cable collection all inherited from various places is a mix of 50, 75 and unknown. My test gear is also a mix of vintage 600 ohm and more modern high Z stuff. I made a 600 ohm terminator from two 1K2 resistors which I use rarely.

Andy.