Subject: Re: How to check for a 50 or 75 ohm connector
Summary: What do you think of these ping times eh?
Reply-To: You can't see me, and I pass right through planets...
References: <3E053579.AFE0BFDF@sympatico.ca> <3keudKjAZXB+Ewcs@newbrain.demon.co.uk>
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Date: Sun, 22 Dec 2002 18:12:00 GMT
NNTP-Posting-Date: Sun, 22 Dec 2002 13:12:00 EST
On Sun, 22 Dec 2002 15:31:56 +0000, Don Pearce
>Of course, now I think about it - the diameter of the pin doesn't
>actually do anything for the impedance of the connector when it is
>mated. It is the outer diameter of the female jack that forms the
>impedance-determining dimension in the connector.
Center conductor diameter is also a factor, as the rules for a
capacitor are area factored. The surface area of a larger center wire
is greater. The shield is one plate, the center wire the other.
The final determining factors are distance between the plates, and the
dielectric used for the center conductor insulator, and the surface
area of the proximal plates. The shield and the center wire of a
given cable length ARE those two "plates".
I regularly make HV capacitors at my work place by using a specific
length of 60kV HV coaxial cable. Leaving the tail end open, end
sealed against flashover (six inch encapsulated tail), the cable
itself makes a perfect HV capacitor.
You should see the coils jump when they get charged up (I coil the
length up with tie wraps).
By the rules that determine capacitance, the center wire diameter
MUST be part of the equation. Think about it.