One interesting thing was observed during the strike to my tower. I was in the
shack when it happened. It was dark outside and I saw a brilliant light and
felt a pressure similar to the mortar blasts experienced during military basic
training (combat simulation), but no sound at all. I assume I was inside the
plasma envelope that causes the thunder upon collapse. It was weird.
73, Keith NM5G
-----Original Message-----
From: TowerTalk <towertalk-bounces@contesting.com> On Behalf Of K9MA
Sent: Wednesday, September 4, 2019 4:46 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Grounding
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@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@mardock.us
> j@KRØP.us
> 402-525-6111
>
> -----Original Message-----
> From: Howard Hoyt
> Sent: Wednesday, September 4, 2019 13:38
> To: TowerTalk@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@sdellington.us
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