[kwlug-disc] Home made indoor TV Antenna

John Johnson jvj at golden.net
Thu May 1 22:53:27 EDT 2014


On 2014-05-01 16:14, John Johnson wrote:
> ** Almost nothing will protect against a direct lightning strike as 
> the energy to be dissipated is just too high. Typical protection 
> circuits are intended to protect against lightning induced voltages, 
> i.e. those voltages induced in conductors near a lightning strike and 
> induced by the rapidly changing magnetic field around the strike.

On lightning and lightning induced surge voltages:
In the days of dial-up (and expensive PC hardware) I preferred external 
modems as I considered these to be sacrificial as compared to the PC.
Inside of 10 years, I replaced 3 modems on my sister's PC when the 
modems were bricked as a result of lightning induced surges during storms.
She lived in Waterloo near Weber and Marshall on a lot that backed onto 
a park and where there large and high trees. And a high water table.

I also replaced a couple of dial-up modems at my place until I went DSL. 
I and still use a rental DSL modem for the same reason, sacrificial 
protection.
And, a few times, I have had the DSL modem replaced by the ISP after it 
was bricked during a storm.*

I also have a few trees in my area. And the phone lines through and near 
these trees.

I prefer to have the lightning induced voltages reduced by the external 
equipment before the cabling brings the voltages into the box or router.

* I know the cost of DSL modems has dropped over the years and that 
replacement units can be had for much less cost than before.

PS: In about 1978, I gained a healthy respect for lightning, having been 
dispatched by my employer to travel to the Pembroke area to repair a 
rural T1 carrier system that had been damaged by a lightning strike in 
the area. I had to replace most of the circuit boards in the 2 metre 
high rack mounted system as well as the backplanes. And then wirewrap 
the interconnect.

JohnJ
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