Hello, again;
In days of old, before everything had electronic components, the
threshold voltage above which appliances were damaged was quite high and
the threshold for the power cords was, in some cases, about the same as
that for motors and other electromechanical components. The power cords
on the AC units broke down and protected the other components. Either a
small increase in impedance or a physical decrease in breakdown voltage,
both affected by tying knots, may have caused the cord to fail first.
Lightning threatens people and equipment, especially solid state
equipment. Shield your equipment with high impedance devices at the
point of entrance into the shack and with multiple low impedance paths
to ground, via multiple ground rods and as many Ufer grounds as you have
available outside the shack.
73 de WO?W
Jim Wilcox wrote:
>Several years ago, I was quite fortunate to attend a seminar about lightning
>protection presented by one of GE's lightning experts. He had worked for
>their mobile radio group in Lynchburg, VA. Unfortunately, I can't lay my
>hands on the notes I took, or remember the man's name. (I do remember that
>his surname was the same as that of a popular folk singer--maybe
>"Guthrie"--funny how the mind works! I'll probably find my notes or
>remember his name right after I push the "send" button.) He was a ham, and
>I believe he became an SK a few years ago.
>
>One of his stories (he was a most delightful speaker) was about working in a
>lightning-prone area where some appliances (primarily air conditioners, as I
>recall) were being damaged or ruined by surges induced by lightning. He
>hypothesized that tying overhand knots in the power cords would provide good
>protection. Interestingly, as I recall, he also suggested six knots. As I
>recall (I hate to keep saying that), he said that they never lost another
>air conditioner after that.
>
>He showed us a power cord that had been taken from an AC unit after a storm.
>It had a half-dozen knots in it and several of them obviously had been
>"fried" by high voltage--melted insulation. etc. He said that the AC unit
>had survived.
>
>Knots in power cords? You betcha!
>
>73
>
>Jim, W3WV
>
>________________________________
>Jim Wilcox
>
>----- Original Message -----
>From: "Red" <RedHaines@centurytel.net>
>To: "James" <jameswarren@swbell.net>; "Towertalk" <towertalk@contesting.com>
>Sent: Saturday, 12 July, 2003 09:48
>Subject: Re: [TowerTalk] Re: lightning suppression on cable
>
>
>A high percentage of the energy in a lightning strike is in the spectrum
>under 1 MHz. I don't think tying knots in the line will impede it much.
>
>73 de WO?W
>
>James wrote:
>
>
>
>>>I get both TV and Internet via TV cable. It is the last conductor coming
>>>into my house that is not protected by a lightning or surge suppressor, or
>>>disconnected when not in use. Can anyone suggest an appropriate
>>>suppressor for this purpose that will pass both TV and 2-way Internet
>>>signals (low HF to high UHF)?
>>>
>>>
>>>
>>>
>>I've used commercial grade coax lightning arrestors for commercial
>>two-way and cellular antennas. Very expensive, but the work and are
>>almost invisible when you do a TDR line sweep, even at 1900 MHz.
>>
>>At home, I tie six knots in my power, control, and antenna lines before
>>they come into the house. Eveything is inside a metal box WELL grounded
>>with several eight foot long grounding rods. The high "frequency" of
>>a lightning bolt (actually the DV/DT) has trouble even making a right
>>angle bend, much less an entire knot. For this reason, ground wires
>>need to be routed to a ground with no turns; but if neccessary, a gentle
>>curve..
>>
>>
>
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
>questions and ask for Sherman, W2FLA.
>
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>
>
>
>
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