Re: 50 ohm cable - wrong BNCs!

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From: Arthur Moe (kb7ww@easystreet.com)
Date: Thu Aug 15 2002 - 10:23:41 CDT


Leon,

Is not 75 Ohm SMALLER than 50 Ohm??? At least the center conductor of the
cable is.

Art
KB7WW

Leon Heller wrote:
>
> I've just received a couple of 50 ohm cables with BNC connectors at each end
> from one of my usual suppliers, for connecting test equipment. I normally
> make my own, but I was out of BNCs, and making up cables isn't one of my
> favourite activities.
>
> I checked the connectors (I do this automatically, having worked in R&D for
> many years), and was rather annoyed to find that they appeared to be the 75
> ohms variety (the central conductor pin is slightly thicker, and less
> 'pointy'). The cable itself was correct - RG-58.
>
> The supplier is investigating the problem. They've probably sold thousands
> of them, without anyone noticing.
>
> It's worth checking this sort of thing. Putting a 75 ohm plug into a 50 ohm
> socket can spread the mating part of the socket, so that subsequent use of
> the correct plug could result in a poor contact. The impedance mismatch
> won't be noticeable, unless you check all your cables using TDR.
>
> 73, Leon
> --
> Leon Heller, G1HSM
> leon_heller@hotmail.com
> http://www.geocities.com/leon_heller


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