Ya know gentlemen; I think that some of you should gather and contribute your
vast knowledge of grounding and lightening protection to establish a standards
document that Hams can use.
Imagine a standard that all Hams could reference that has been vetted by those
who's credentials and industry experience provide a truly usable and safe
reference for all.
A lot of what I read is accurate, but some of it is questionable in my mind
based on my industry training and experience in telecommunications and now
hospital building construction. I've used IEEE, BICSI, TIA, ANSI, NEC and
other similar references and they all collide at some point in the way to
provide ground (earth) and lightning protection. I share all that because this
debate has me confused at different points, and I can't imagine how the humble
Ham who's a Dentist, truck driver or whatever their profession is - try to
follow along and gain a general understanding of grounding and lightening
protection (two different disciplines with commonality).
We all could benefit (and save our stations) by some of you really smart and
well versed chaps gathering and hammering out a standard we could all live and
operate by.
Be well, operate safely during the storm season and save your loose change for
a Patriot. Jim Whalton gave me the run down yesterday at the TT booth... it
looks like fun.
73 - Eric
W9WLW
On May 16, 2014 7:47:03 PM EDT, Robert <rmcgraw@blomand.net> wrote:
|I had 3 pieces of 1" braid in place to bond the rotating mast to the
|sleeve at the top of my tower. A lightning strike burned all 3 into.
|Balled ends on the strands confirmed this.
|
|73
|Bob
|
|
|Sent from my iPhone
|
|> On May 16, 2014, at 6:04 PM, Stuart Rohre <rohre@arlut.utexas.edu>
|wrote:
|>
|> Jim, don't we all use Flukes now? :-) I do have several at home and
|work. I was remembering a discussion of a rig fault where the pin
|intended for grounding, had not been grounded at the radio connector
|entry to chassis.
|>
|> Good point you make about low ranges needed for ohms measuring.
|There are some good build it yourself low ohms measuring circuits out
|there, to extend the range of an ordinary meter. The Graf (author)
|series of circuit diagrams books includes at least one. The ham
|magazines in last 40 years had one or more.
|>
|> In the midst of measuring things, most good troubleshooting includes
|a thorough visual inspection to see how things are bonded and grounded,
|and if the circuit board is providing the connection to chassis.
|> Unfortunately, we had not done a pre service inspection of the
|following radio incident:
|>
|> For high current faults, we have seen a Yaesu 5100 that had RF
|connection to circuit board and its DC negative power line to same
|circuit board at other end of chassis. A lightning event on the tower
|induced shield current down the coax to the radio , across the circuit
|board, vaporizing part of the ground copper, and then to the DC
|negative line which returned to AC third pin and power supply chassis.
|>
|> The bonding was done by an experienced power plant engineer, but it
|provided an extra return path through that circuit board trace, that
|caused severe damage to the trace. Luckily, that radio has survived
|that, with a bus bar now bonding DC negative to the coax connector
|shell external to the chassis. (No longer relying on the radio circuit
|board traces.) The radio worked even after losing part of the board
|copper, but only if the coax was connected, which was grounded to the
|tower and earth providing a return through the AC third pin. That
|observation prompted us to open the radio, which then showed the
|missing trace.
|>
|> As for braid failures, literature about high current faults has
|stated that braid can blow apart in a near direct strike, as little
|shards of wire. Indoors in someone's shack that could cause injury, or
|put small shorts into places hard to find.
|>
|> Copper flashing could be used in place of braid. The use or either
|was to provide low inductance through wide flat conductors used for
|bonding equipment together.
|>
|> Stuart Rohre
|> K5KVH
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