Al Williams wrote:
>----- Original Message -----
>From: "K4SAV" <RadioIR@charter.net>
>Sent: Friday, January 05, 2007 11:23 AM
>Subject: Re: [TowerTalk] Antenna/Tower Grounding (Lightning Protection)
>>I was once called in to debug a
>>problem on a piece of electronic hardware, and when I got to looking at
>>it, the designer had run all the many grounds off each of the PC cards
>>and had taken them all back over 3 feet of wire and tied them all
>>together at one common point. What a disaster that was. Another case of
>>someone thinking that an SPG means only ONE ground.
>>I wish I could wipe the term completely, but it is firmly engrained in
>If your name was Hal, then the designer tying the PC card grounds back to a
>common point could have been me except that the run was less than 3 feet!
>After studying "proper grounding techniques", I chose to do a single point
>ground for each PC card in the 19 inch assembly of cards and then each
>assembly to a rack single point ground and on to the actual ground on the
>floor. This rack was an automatic wafer IC test set and contained about a
>thousand IC chips and about a thousand transistors so it was difficult to
>try to pinpoint the cause of the many anomalies that were occurring.
>After a couple days of debugging, my technician, Hal decided to change the
>card ground wires from the single point to the nearest ground. The
>anomalies went away and Hal went out to a free dinner! That occurred about
>25 years ago but I still remember it very clearly.
That wasn't me, but it's just another illustration of how misleading the
SPG term can be. Many people were on the steep part of the learning
curve around the time TTL and then Schottky logic appeared.
TowerTalk mailing list