That is a great question. I also have a tall crankup and am in a very
corrosive salt air environment where is difficult (not impossible but one
has to be methodical) to seal off connectors using all the best practice
methods. I'm now using the flooded heat shrink and 3M liquid seal on the
shrink ends over connection joints and connectors where I can. Liberal use
of CorrosionBlock on the connector threads and tips too. How would one
terminate/bond the coax shields at the tower top in a manner that would not
leave something open to potential corrosion?
Don W7WLL
-----Original Message-----
From: N3AE
Sent: Saturday, November 01, 2014 9:44 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Terminate braid at top of tower...or not?
I've always wondered about terminating coax shields on the top of a crank-up
tower. On one hand, I think that by doing that, you're encouraging lightning
currents to go down the coax shield as the resistance between the tower
sections of a crank-up is likely to be larger than the coax shield (assuming
the shield is also bonded at the bottom of the tower). But perhaps the
inductance of the coax is larger than that of the tower so most of the
lightning current would still traverse the tower? On the other hand, by
bonding the coax at the bottom and not at the top, you may have flash-over
issues at the top because of the difference in potential of the tower and
the coax shield at the top. Maybe I'm making this more complex than it is,
but my gut tells me it is a bit more complex than it may first seem.
All the commercial towers bond coax shields at the top, bottom and every
70-100 ft or so, but they are not crank-ups with unknown continuity between
the sections.
N3AE
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