[TowerTalk] Grounding

Wed Sep 4 17:46:03 EDT 2019

My tower hasn't been hit yet, but something about a half mile away got 
seriously hammered the other night. I haven't heard of any damage, but 
it must have awakened the whole neighborhood. Just a little reminder.

73,
Scott K9MA

On 9/4/2019 16:35, Bob Shohet, KQ2M wrote:
> Stop a direct hit?   No!
>
> Make your appliance less likely to be damaged or destroyed?   Yes!
>
> There are no protection absolutes when it comes to lightning strikes.  All you can hope to do is make your valuables less inviting of a target relative to other potential targets, and provide the shortest low resistance paths to ground in an attempt to help divide up and “control” the effects of that strike.
>
> I too make sure to disconnect EVERYTHING in my shack when not in use during the lightning months as well as when it appears that a T-storm is on the way.  Grounding alone is not enough at this qth.  You must disconnect everything INSIDE.  That is no guaranty either but it does afford an additional level of protection, the vast majority of the time.
>
> I have had EMP’s from strikes on my towers that have been so powerful that they have lit up my TV’s even though we had lost electrical power, and 18 years ago actually caused a battery operated doll of my daughter’s to start walking and talking!  I have also lost a few circuit boards inside one of my FT 1000MP’s and a 2 meter radio in that same storm.  Nothing was attached to either of those radios at the time.
>
> I have also had lightning come into the house through the phone lines, cable lines and the well.  One strike on my tower two years ago (when everything was disconnected!) actually induced a big ZAPPP! in my the radiator in the kitchen – and a nasty arc between the radiator and the wall that gave off a burning smell.    In the 21 years that I have had my two towers up, and taken probably 10 or so direct and indirect hits, that had not happened before or since.  We are still not quite sure how that happened since nothing else was affected.
>
> Use all the lightning protection that you can and disconnect everything when not in use!
>
> 73
>
> Bob KQ2M
>
>
> From: John Mardock
> Sent: Wednesday, September 04, 2019 3:17 PM
> To: TowerTalk at contesting.com
> Subject: Re: [TowerTalk] Grounding
>
> If lightning propagates several thousand feet through the air to get to your
> Antenna/Shack/Home does anyone think a small gap arrestor is going to stop a
> direct hit? Silly question, yes?
>
> John Mardock KRØP
> j at mardock.us
> j at KRØP.us
> 402-525-6111
>
> -----Original Message-----
> From: Howard Hoyt
> Sent: Wednesday, September 4, 2019 13:38
> To: TowerTalk at contesting.com
> Subject: [TowerTalk] Grounding
>
> Keith, all,
>
> I will amplify this a bit; a direct strike to anything on or within the home
> can be catastrophic.  I'm a broadcast engineer and I will not degrade list
> s/n by elaborating how extensive grounding systems are in our broadcast
> facilities.  Even so I have seen some very scary results of lightning such
> as a helical element on an FM panel array fused into a ball of copper, and
> even with these spec ground systems I've seen damage to equipment on the
> ground. 6" hardline has a pretty high peak voltage rating, 50 kV or more
> when pressurized and I have seen loading caps in PAs burnt up by
> lightning-initiated transients, followed by the HV PS feeding the arc.
>
> Due to my 'respect' for lightning and what I have seen it do, I have always
> been very wary with my ham setup.  When not in use or when lightning is
> anticipated I actually disconnect the feedline where it enters the house,
> and walk it 30' away under a tree and stick the PL-259 into a clean dry wine
> bottle.  As a result I have never suffered equipment damage in my house due
> to lightning striking my ham antenna.  Damage to the antenna, sure, but that
> was all.
>
> Just about a year ago I had lightning strike my TV antenna, which was on a
> 20' mast grounded with an 8' rod and a gas-tube "F" connector arrrestor.
> The antenna was lower than the peak of my house and under 90' trees, but
> lightning, likely a side-strike found my TV antenna.  It melted the end of
> one of the alumninum elements, and then followed the RG-6 into my house and
> got to work.  It destroyed the TV which was wired ethernet connected to my
> router.  From there it propagated everywhere wrecking audio/video/all IT
> infrastructure/PCs/PV Inverters/electronics test bench equipment.
> Fortunately the ham gear, not being ethernet connected was largely spared
> other than the USB dongle and minor grounding damage.  It vaporized Cat 6 in
> places, and has taken me months and ~$30k to remediate.  Thanks to an Eaton
> commercial TVSS in my main panel no damage propagated via H/N/G AC wiring
> differentials.  As a side note I HIGHLY recommend Auto Owners Insurance, I
> was getting deposits in my account hours after submitting invoices.
>
> In order to minimize a re-occurrence I have optically coupled the Ethernet
> and HDMI connections to the TV.  I looked into a broadband uV level optical
> converter to isolate just the TV antenna but there is currently no such
> animal, so as of now if lightning hits the new antenna the TV is
> sacrificial.  Some have asked why I just don't do Wifi with the TV, and that
> its because I like 4k HD content which has not been reliable with WiFi
> despite optimal TV IP configuration.  Others have stated if the TV mast
> ground was bonded to my house ground no damage would have happened, but
> although a good idea, it is likely to have made little difference in the
> outcome.  The TV mast is 50 feet away from the main panel and it's ground
> rods.  Any conductor, even if punctuated with rods every 16 feet would have
>> 28 uH of inductance and high capacitance to the earth, so the resulting
> transient would take >100 nS to reach the house ground and equalize the
> charge there.  In the meanwhile due to ground potential rise the earth
> around the TV ground rod and the TV coax shield are at perhaps tens of
> thousands of volts of potential differential to the house AC system and all
> connected devices.
>
> As is the case with broadcast facilities, it would be optimum to have all
> external utilities enter at the system grounding point as I have done at FM
> stations, so maybe I will move the TV antenna...
>
> This situation exists for most homes with TV antennas, wireless dog fences
> and other wiring external to the house, so be prudent!
>
> Just my 2¢ worth.
> Howie / WA4PSC
>
>
>> >from [Keith Dutson] NM5G
>>> My experience is that lightning can be managed, to a point.
>>> A direct strike to your tower can be catastrophic.
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-- 
Scott  K9MA

k9ma at sdellington.us