[time-nuts] New NTBW50AA

Mon Sep 16 02:25:47 UTC 2013

Don,

Thanks for the suggestion!   I have no doubt that you are correct and 
especially so at the moment of any "strike" or discharge.   But these rods 
cover an area approximately 200 by 500 ft. and I don't find heavy cable 
"practical!"  Feedline varies from the RG-58 you would expect to 7/8 inch 
Andrew (350').

Lee
----- Original Message ----- 
From: "Don Latham" <djl at montana.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Sunday, September 15, 2013 3:54 PM
Subject: Re: [time-nuts] New NTBW50AA

> Lee, if I can make a couple of comments, first, you can have large
> voltage differences among your 23 "ground" rods, depending on the ground
> terminus of the lightning strokes. Second, antennae and feed lines that
> do not attract lightning due to being "hidden" can still be subject to
> large induced voltages.
> I'd suggest all the ground rods and antenna bases be connected directly
> with large cable so they are all truly at the same ground potential...
> Don
>
> Lee Mushel
>> Lightning is certainly one of Old Mother Nature's principal weapons as
>> well
>> as being extremely unpredictable.   My House/Shack is on the side of a
>> hill
>> with the Antenna Farm on top of the hill about 120 yds away with an
>> additional 30 ft. of elevation.   There is a metal "lightning rod"
>> extending
>> high enough to provide a "cone of protection" for the house and is
>> grounded
>> directly.   And there are five other metal antennas on that roof, two to
>> a
>> separate ground and three to still another which is close to the shack
>> "ground field" which is three additional  ground rods.   All ground rods
>> I
>> mention are the standard 8 ft. copper plated steel items.  Each of five
>> antennas in the antenna field also have individual ground rods and I
>> guess
>> if you follow the cable shields you could say that they are all
>> connected
>> together.    A couple of years ago I counted all ground rods and came up
>> with 23.   Before all of the metal was added and the "lightning rod" was
>> the
>> only metal extending about 20 ft. above the roof and we had an
>> electrical
>> storm my wife would complain that she could feel her hair trying to rise
>> in
>> response to the field coming from the cable which ran across the roof
>> and at
>> it's closest point was only 6-7 ft. from her head as the crow flies.
>> But
>> after all the additional metal was added in the form of antennas with
>> grounds  she no longer complained.
>>
>> I do not claim to understand what goes on around here at an elevation of
>> about 102 ft. above the valley floor but I believe that we have been
>> "fortunate"  (or lucky if you prefer that word) and we have so much
>> metal in
>> the air that most "discharges" are not of the type that is accompanied
>> by
>> thunder!   Two years ago we had a tree die that was no more than 30 ft.
>> from
>> the house.   Since I have not always been able to accurately predict
>> where
>> trees will fall that I cut myself I hired a professional to take it down
>> and
>> he took one look at it, reached up and stripped off a piece of bark and
>> commented, "See those lines?   This tree was struck by lightning.
>> That's
>> what killed it!"   But no lightning related damage to structure or
>> equipment
>> here for nearly 15 years!
>>
>> My only thought on the subject was that only a fool would fail to
>> disconnect
>> an antenna that rises above the house roof  during an electrical storm.
>>  I
>> freely admit that I have several ham radio VHF antennas  (and a GPS
>> antenna
>> supplying the disciplined system for frequency reference) well below
>> roof
>> peak level  (clear view to south for GPS, of course) that I do not
>> disconnect from inexpensive radios maintained for the purpose.
>>
>> This is risk I accept.   And I certainly have seen paths followed by
>> lightning that are truly amazing!  ....and horrendously damaging.  Never
>> forget that you only live once and you do have a perfect right to enjoy
>> your
>> hobby without fear.
>>
>> Regards,
>>
>> Lee A. Mushel   K9WRU
>>
>>
>> ----- Original Message -----
>> From: "quartz55" <quartz55 at hughes.net>
>> To: "Discussion of precise time and frequency measurement"
>> <time-nuts at febo.com>
>> Sent: Sunday, September 15, 2013 12:13 PM
>> Subject: Re: [time-nuts] New NTBW50AA
>>
>>
>>  .  I'm not thrilled having it above the beams, it's the highest metal
>> thing
>> in the area and most likely more prone to lightning than anything else
>> excpet the trees and it will blow around a bit up there as well as
>> rotating
>> once in a while.  I did have a strike here once, but it was down by the
>> barn
>> and was looking for the underground telephone cables, it blew apart a
>> post
>> and knocked off the boards, it was maybe 100 yards from the shack.  It
>> wouldn't be much of a problem to dig a tiny trench to the fence and I
>> may
>> try that after this precise survey is done, then do another and see if
>> anything changes.  I could hide it i
>>> n a bird box at the fence too.  After all at this point I'm just
>>> playing.
>>> I'll eventually make up my mind.  Also, I don't have an attic, so
>>> that's
>>> not an option.
>>>
>>> Dave
>>> N3DT
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>>
>>
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>
>
> -- 
> "The power of accurate observation is commonly called cynicism by those
> who have not got it."
> -George Bernard Shaw
>
>
>
> Dr. Don Latham AJ7LL
> Six Mile Systems LLC
> 17850 Six Mile Road
> POB 134
> Huson, MT, 59846
> VOX 406-626-4304
> Skype: buffler2
> www.lightningforensics.com
> www.sixmilesystems.com
>
>
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