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Ground/size

Subject:  Ground/size
  Date:   Mon, 5 May 97 12:38:52 EDT
  From:   pierson-at-ggone.ENET.dec-dot-com
    To: 
       
mail11:;;;;;;-at-us4rmc.pko.dec-dot-com-at-us4rmc.pko.dec-dot-com-at-unknown.domain.pupman-dot-com;;;;;;;;;;;;;;;;;;;
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        pierson-at-ggone.ENET.dec-dot-com


[I've reformatted, by hand, to 70ish, as it arrived this way:]

>I read about the importance of a high current ground, and the use of
>heavy 
[reformatting]

>wire to connect to it.  Yet the secondary wire isn't all that big.
>I'm using 24 gague on a 4 inch secondary - if I remember right the
>largest wire size on a secondary I've read about on the list is
>18 gauge???   What I don't understand is why the wire from the
>secondary to the ground rod (or whatever) needs to be more than one
>wire size (or 2) larger than the wire that the secondary is wound
>with.
        Two reasons:
        1) the ground wire is 'going somewhere' so it needs to be
        relatively larger to avoid adding loss, due its length.
        Both inductive 'loss' and resistive loss.

        2) (and more important, imo) is that the Current in the
        secondary is NOT the DC or LF AC current, which is constant
        thruout its length.  It is current in a phsycial resonator
        which means that it can VARY thruout its length.  Just as
        the voltage risses at the top, the _current_ rises at the
        bottom.  While the bulk of the coil may be carrying 'amps'
        the ground may be carrying 10s of amps.

        [All of this ASSumes 'classic' 1/4 wave, grounded base
        secondaries.  And may be LESS applicable to 'magnifier'
        operation....]

        [The 'logical extension' of this would be secondaries wound
        with differing gauges of wire.  I believe this has been tried,
        with no significant benefit, at least given the hastles...]

>IT would seem to me that current is limited by melting the secondary
>wire.  Can someone explain.
        Melting would take place at much higher currents than are
        involved.  Choice of wire size should be governed by 'big
        enough not to have losses'.  (Solid strap, tho not,
        apparently, braided strap, are other options.)

        regards
        dwp