On 5/9/2013 9:06 AM, Al Kozakiewicz wrote:
The point was that burying brazed joints is common accepted good practice. AM
broadcast ground system are designed for a 30 year lifespan. That being said,
brazing copper wire to a copper clad steel rod is still bonding Cu to Cu
regardless of the substrate.
But this misses Jim Lux's point that these joints are part of the
ANTENNA -- the radial system -- NOT part of a connection to the earth
for safety. This is the problem I have with the use of the word
"ground" to describe so many different concepts in electronics, which
leads to great confusion.
The connection to the EARTH is required for LIGHTNING protection, and it
is mandated both building codes (that is, LAW) and by good engineering
practice. The failure of a single joint could result in the loss of the
earth connection. The connection of the radials is NOT mandated by law,
is ONLY an issue of good engineering practice, and there are MANY
connections in parallel, so the failure of a single joint is less of a
problem.
As a young EE student, I spent the better part of a summer
silver-soldering a replacement radial system for a 4-tower AM
directional on 930 kHz. BTW -- the reason we were replacing the radial
system was that we were having trouble maintaining the nulls in the
antenna pattern, which was a very big deal in those days because the FCC
actually DID something to enforce their Rules, and in this case, those
nulls protect stations in certain directions from interference. :)
73, Jim K9YC
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