[RFI] Lightning Protection Re: RFI Digest, Vol 114, Issue 1
Fred Stevens K2FRD
k2frd at mac.com
Sun Jul 1 13:25:18 PDT 2012
Pete et al--
In my 51 years of experience in ham radio including 24 years in the Army Signal Corps, I have long learned that lightning is like the 800-lb gorilla: it goes where it wants to go despite all the preventative measures one takes. I come from upstate NY where lightning storms are quite common and I know hams who have had their rigs, antennas, and homes or shacks destroyed even though they had lightning protection devices, e.g., surge and lightning protectors. Lightning doesn't need a direct hit to affect anything electronically attached to the point of contact. In one instance, Tony WB2DTW (now an SK) had a lightning strike on his beam some 40 ft from his home. The strike hit the antenna, traveled down the coax to his rigs in the garage, then proceeded along the power line into his home and eventually found a suitable ground. Everything in between was destroyed from his rigs to the kitchen blender including a major section of his garage. He forgot one thing (see below).
That said, at least some measures might be taken. Better something than nothing if for no other reason than a little peace of mind. There is no such thing as a lightning-proof system. But best protection I've seen are old-fashioned lightning rods such as are commonly found on top of barns but mounted on top of a mast, mounted on top of a second parallel mast, and/or on top of a house... anything to divert the lightning strike away from rigs and other (expensive) things. Main thing is to have the lightning rods ABOVE the antennas and any nearby structures.
Grounding is important but no matter how sophisticated a ground system might be, there's other precautions one might take, e.g., if a lightning/electrical storm appears imminent, disconnect the coax going into your rig(s) and get it as far away from everything as possible (Tony had done this yet his rigs were still destroyed.), and UNPLUG the rigs and the other expensive items such as refrig, freezer, TV, computers and peripherals. If there's a nearby (say 20+ miles) lightning storm, you'll hear the crashes on whatever band if you're on the air. Same/same landline telephone via which lightning will travel (I know of people killed while on the phone.).
Some details: http://www.iceradioproducts.com/10.html (see Paragraph 3). The League also provides a wealth of information on the subject http://www.arrl.org/lightning-protection .
But again, lightning goes wherever it wants.
73 de Fred Stevens K2FRD
At 12:00 PM -0700 1/7/12, rfi-request at contesting.com wrote:
>Date: Sun, 01 Jul 2012 10:28:56 -0400
>From: Pete Smith N4ZR <n4zr at contesting.com>
>Subject: [RFI] Single-point grounding
>To: RFI List <rfi at contesting.com>
>Message-ID: <4FF05EA8.6040707 at contesting.com>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>I'm not sure exactly where I should post this, but suspect that this
>group probably has more relevant expertise than most, so please bear
>In the last year, I have had two expensive episodes. In both cases, my
>transceiver's RS-232 transceiver was fried during a lightning storm, and
>several knowledgeable people suggested a difference in chassis potential
>between computer and transceiver as the reason. Their prescription for
>avoiding a repetition was simple - connect the chassis of all of the
>units to a single-point ground.
>My solution - which I'm asking people to critique - was to fabricate an
>L-shaped, roughly 3x5 foot ground bus made from 3/4" copper tubing,
>which I mounted on the back of my L-shaped operating desk. All joints
>are silver-soldered. I then connected each of the affected units to the
>bus with very short and heavy stranded wire, and connected the end of
>the bus to my grounded shack entry panel (in a double-hung window).
>The DC resistance of the ground bus is very low, but the length
>approximates a quarter wave on 10 meters, and with the units connected
>near the ends of the bus, I wonder if I'm feeling a false sense of
>security about the likely behavior of the bus during a nearby lightning
>event. Would I be better off (or no better) running heavy conductors
>from each unit to the entry panel, even if they would have to be
>similarly long? Or should I just give up and plan on disconnecting the
>RS-232 connection whenever weather approaches?
>73, Pete N4ZR
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