[TenTec] humm

[Gary Hoffman]

Resistance is indeed the evil.

If one's bonding is inadequate - and it mostly is NOT !!! - then you are 
defeated.

And there can be sneak circuits...and again you are defeated.

And a direct hit....unless you have a ridiculously oversized system....you 
are defeated.

BUT....for the common man....a really well designed home system buys you a 
lot of security against
quite serious events, short of armaghedon (however you spell that ...grin)

I have such a system, wayyy overdone, and I've survived some amazing stuff. 
In fact, never had
any damage at all...period.

Lucky I guess !

73 de Gary


----- Original Message ----- 
From: "Stuart Rohre" <rohre at arlut.utexas.edu>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Wednesday, November 25, 2009 6:06 PM
Subject: Re: [TenTec] humm


> Actually Gary, what you say would be true in theory,  but for the mortal
> character of wire resistance.  That is what allowed the surge to come
> down the coax shield, (low R) and travel thru the coax connector, (low
> R, to the circuit board traces to the power leads (higher R) and then
> out the power negative (medium R) to the Astron negative terminal that
> was tied to its case (higher R), which was also tied to the 3rd pin AC
> ground wire (Highest R).
>
> Enough current was dissipated at each of the changes of wire/ conductor
> gauge, to burn out components in the Astron; and in the rig, it
> vaporized a section of circuit trace.
>
> Yes, in theory, you bond all grounds (outside the shack).  In practice,
> if you have coax in parallel with a Chassis ground braid wire and AC
> third pin wire, you may have a failure, if you also have a high
> resistance crossing of AC and DC grounds inside the equipment.  The
> change of gauges of the conductors was the resistance choke point for
> the surge.
>
> This same surge took out the top of a power pole across a parking lot
> from the shack.  Apparently a two stroke leader from the main lightning
> event!  The pole was toothpicks down to the guy wire, which grounded out
> the stroke, since it was larger and lower R than the copper pole ground
> wire.
>
> AC grounds, antenna coaxes, and phone and internet ground connections
> should all bond outside the building per NEC electrical code.  There
> should be a metal entry panel with surge devices grounded to the
> perimeter ground conductor placed to protect the whole building.  Even
> this will not prevent some damage but mitigates most lightning events to
> radio and TV stations.  Their towers are designed to take hits and come
> right back on the air in most cases.  Their feedline gauge and element
> diameters are typically much larger than ham grade antennas and towers
> and feeds to enable this.
>
> -Stuart Rohre
> K5KVH
>
>
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