I think I know why. I worked on such computers, and they were very sensitive to ESD. If you touched the cabinet during the winter, when it's very dry, the spark would be enough to crash the computer, although permanent damage was rare. The problem was that the computers were under-designed back then. Now days, all such electronics has to pass a variety of ESD and power surge tests. Not that they will necessarily survive a full surge. For this, one buys a large surge arrester and installs it on the power panel.
Joe Gwinn From: EB4APL <eb4...@cembreros.jazztel.es> To: time-nuts@febo.com Date: 04/12/2012 07:00 PM Subject: Re: [time-nuts] Best location for a GPS antenna...? Sent by: time-nuts-boun...@febo.com Hi, I have a personal reference: In the Deep Space tracking facility where I used to work some 20 years ago it was very common to have minicomputers damaged by strikes in the antenna. This antenna was located about 1000' from the control room and there were an elaborate grounding system both in the antenna (mainly intended to protect from lightning) and in the control room, but we got TTL chips damaged very often during thunderstorms. The common believe was the high currents induced in the ground cabling caused voltage spikes inside the computer cabinets enough to fry the chips. I don't remember failures in the receivers, transmitters or other subsystems, but minicomputers were the usual targets, one or two chips each time. Regards, Ignacio, EB4APL On 12/04/2012 23:21, Bob Camp wrote: > Hi > > Do you have a reference for 100' distant strikes routinely destroying > receivers? > > Bob > > -----Original Message----- > From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On > Behalf Of Chris Albertson > Sent: Thursday, April 12, 2012 3:25 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Best location for a GPS antenna...? > > On Thu, Apr 12, 2012 at 11:56 AM, Randy D. Hunt > <randy_hunt...@yahoo.com>wrote: > >> On 4/12/2012 1:10 AM, Heinzmann, Stefan (ALC NetworX GmbH) wrote: >> >>> What about mounting the antenna on the side of the metal pole, with the >>> top of the pole extending a foot or more above the antenna? >> > Typically when a receiver or other radio is destroyed it was NOT because of > a direct strike. A strike within maybe 100 feet is enough. There is a > _huge_ EMP field around the strike. The field will induce large currents > in any nearby conductors. Even if the strike is to bare Earth many feet > from the antenna the potential of the earth is raised by say 1,000 volts so > now anything connected between ground the power has 1KV across it. > > > > > > Chris Albertson > Redondo Beach, California > _______________________________________________ > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
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