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SNLA188.pdf Broadcast Video Owner's Manual

Hugh3226
Prodigy 30 points

SNLA188.pdf Broadcast Video Owner's Manual

Page 23 Section 2.1.3.1 of this manual, titled: "Copper thickness vs. frequency range";

IMHO this is completely brain-damaged explanation.  If you follow the thinking in this section, what thickness of copper would I need to carry 50Hz audio?

I'm sure there is a nugget of fact / truth in here but what is it?

Perhaps it got 'edited' by someone who is not familiar with the subject.  "This would never have happened in Bob Pease's day." ;-)

Perhaps someone out there would like to contribute a corrected version and perhaps reference the literature from which this advice was distilled.

  • 0
    TI__Genius 13475 points

    Hugh

    Section 2.1.3.1 is specifically dealing with RF frequencies, where we are dealing with transmission line effects.   The skin effect means that the electric field only penetrates a certain depth into a conductor, that depth being proportional to the SQRT of the frequency.   The practical effect that this has is that when you are dealing with a high frequency signal, the only thing that matters is the very surface of the conductor, so a gold plated connector will work just as well as a solid gold connector.

    What section 2.1.3.1 is dealing with is the fact that for a transmission line, the skin effect operates not only on the conductor carrying the signal, but the ground reference plane as well.   If you have a well designed transmission line with a ground plane which is thinner than a few skin depths, then the losses that you see when using that transmission line will be greater than you might otherwise expect.

    When we get into audio, you are now operating in a realm where the bulk of your losses are resistive, and for that, as you make the copper thickness and trace thickness greater, your losses decrease,   However, the physics still works, you would find that if you connected an audio signal to a load via a copper wire, you would find that the losses would decrease as you made the wire thicker, up to a certain point, and after that point, you could use wire that was much thicker, with no less loss to the signal. 

    I will make sure that when the broadcast video owners manual is next edited, this section will be made more clear.