Jim Brown wrote:
>On 4/16/2012 3:54 PM, Bob Ad5vj wrote:
>> I was always told to use flat braid for station grounds in years past
>>for RF purposes and if you didnt have any, make it from coax braid.
>Actually braid is NOT a good choice for bonding grounds outdoors,
>because it corrodes so quickly.
In more detail...
The problem with corroded braid is the poor contact between adjacent
strands. This is important because the skin effect keeps the RF current
on the outside surface of the entire bundle of wires - RF current does
NOT follow the individual strands as they dip beneath the surface. So as
each individual strand dips beneath the surface, the current has to
cross over to an adjacent strand, always staying on the outside of the
The mechanical contact force between adjacent strands of braid is very
poor at the best of times, and easily destroyed by even the smallest
amount of corrosion. Although braid allows many parallel current paths,
that isn't enough to overcome the damaging effect of corrosion.
Once copper braid has become corroded, the RF resistance shoots up and
the whole thing is junk.
>The better choice is wide flat copper
>ribbon -- it lowers inductance a bit (but ONLY a bit) as compared to a
>round conductor of equivalent cross section, and doesn't corrode as
>quickly as braid.
Well, strictly speaking it corrodes just as quickly :-) The difference
is that continuous strip doesn't have the problem of contact force
between strands like braid does, so the corrosion on strip is far less
73 from Ian GM3SEK
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