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[TenTec] If you ground it - it will come!

To: tentec@contesting.com
Subject: [TenTec] If you ground it - it will come!
From: Randy K4QO <k4qo@earthlink.net>
Reply-to: k4qo@earthlink.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Fri, 05 May 2006 10:19:20 -0400
List-post: <mailto:tentec@contesting.com>
With apologies to "Field of Dreams", what I mean is that just grounding things sometimes means that you are inviting lightning to go to ground there... through your equipment.

In my line of work with commercial radio towers, I have found that sometimes it is a mistake to ground certain items. Improvements in survivability were gained when certain protection points were removed. For example, a serial communication line was protected with a device and was always getting fried along with the device it was hooked to. Removing the protection actually caused the devices to survive for more than three years with no problems. At my QTH, I look for ways to remove paths like was described by the "RIP" post. Details like replacing switcher wall warts with transformer based ones provide a slight measure of advantage. The transformer ones have (admittedly small) isolation from ground and the AC lines. This isolates the router and cable modem (which is attached to the cable!) from the AC mains and doesn't "invite" the surge to use this path to go to ground. I won't go into a full treatise about grounding but if you take the time to personify lightning surges and see what paths it can take to ground (via your AC power plugs), you might see some opportunities for isolation. One more thought - I use a large linear supply with better transformer isolation to power the cable modem and router and my radio supplies are all linears for the same reason. No switchers for me!

BTW, I have heavy surge arrestors at the cable entry point with ferrites on the cable on the house side of things to encourage the surges (that are basically an RF signal) to go to ground at the points I have provided outside the house. Its my own brand of voodoo but it is based on observations garnered at the commercial sites.

This is a topic fraught with lots of opinion and some science and I don't mean that you shouldn't ground your station. The commercial sites frequently have some of the best grounding known to man and still see damage. Of course, at the end of the day, your best defense is to totally isolate your prized possessions during the storms.

73,
Randy
K4QO

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