[TowerTalk] Shack ground

[W2RU - Bud Hippisley]

On Jun 16, 2010, at 7:41 PM, Michael Baker wrote:

> Relocation is also not always practical nor is it inexpensive. 

Agreed.  But I found the losses from damage caused during three earlier storms not inexpensive, either.  And unlike relocating either the shack or the service entrance, they were downright inconvenient because I had no control over their scheduling.

In those three earlier storms, virtually all the damaged or destroyed equipment in the house was in some way connected to _both_ the AC power line and the telephone line.  In particular, in one storm every PC in the house that had a fax/modem connected to the phone line was totally zapped.  Unfortunately, one of those PCs was my rig control / logging PC, with a serial interface to my rig, so my rig experienced some damage, as well.

These three lightning "events" were not caused by direct hits on my house; rather, they were "nearby" hits, perhaps a quarter-mile away, and the damage came from the surges on our (underground) power line and/or our (underwater!) telephone line.  When your AC service and your telco service come into the building at different locations and each is "grounded" at its own separate entry point, you're just asking for trouble if you have equipment connected to both.

So, clearly, some of the impetus to collect the entrance point for these utilities in one spot goes away if one takes care to _not_ connect anything of value directly to the telephone line.  I no longer use PC-based fax/modems; they have been replaced by a single $50 el-cheapo fax machine for outgoing faxes and a free efax service for incoming.  Similarly, my DSL high-speed internet service feeds a telco-supplied modem which then connects only to an inexpensive WiFi node; there are no hard-wired connections from my telephone line to anything in my shack.  Unfortunately, there's not much I can do about the connection from my DirecTV receiver to the phone line but since it's leased equipment the company replaces it when it dies and all I'm out is the inconvenience of a few days without television service.

Next, the remaining issue is whether cables to/from the shack (for RF, rotor & remote switch control, etc.) go through a single-point ground that is allied with the AC entrance ground.  I think, if I were looking at $5,000 or more to relocate the service entrance (or the shack, for that matter), I would simply lengthen all my cables and make sure they came into the shack the "long way around" -- that is, via the AC service entrance point.  Alternatively, I would disconnect them all _outside_ the dwelling after each operating period.

BTW, I am not located in an area of high lightning activity; the three storms that caused damage to equipment were in the course of perhaps a decade.  But one of those three storms occurred totally outside our normal thunderstorm season, on an Easter Sunday morning, with absolutely no warning whatsoever.  It was a single bolt event.  So I don't recommend leaving cables connected until you see a weather report that suggests a storm is coming; you might receive an unpleasant surprise.

Bud, W2RU