[Towertalk] re: bulkhead ground system

[Robin Midgett]

At 09:51 AM 7/24/2002 -0300, Mike Gilmer, N2MG wrote:
>N5OT wrote:
> > > I still just disconnect everything when I am not using the station.

  I agree...

>This is probably the single most effective method for protecting your 
>amateur equipment.  Even the SPG cannot be counted on entirely
>protecting your stuff from nasties.  And one does not need to take a full 
>hit to receive damage.  Close-by hits generate all kinds of
>transients that take out stuff like phones, modems and trasceiver filter 
>switching diodes all the time.

My experience verifies this. I recently took a lighting induced surge. My 
tower is 150' from my house. There are two 8' ground rods spaced 8' and 24' 
from each leg connected to each leg via #4 bare copper. There is a #4 bare 
copper wire buried in the coax conduit trench from the tower to the house, 
with ground rods every 16', terminating at the power service entry and 
bonded to the ground rod there. All my coax runs pass through PolyPhaser 
lighting arrestors, which are mounted to a copper buss bar in the crawl 
space under the house; the buss bar is tied to the ground system via #4 
bare copper as well.
The recent lightning stroke took out my TS-60, which was disconnected from 
the antenna switch (Alpha-Delta) but connected to my 12VDC power 
distribution system (Oak Bay fuse block). Both in-line fuses to the TS-60 
were obliterated. There are burn marks on the coax jumper that goes from 
the antenna switch to the radio; this jumper was lying near the switch, 
disconnected, with the switch in the grounded position. There are also burn 
marks from the metal cover of the fuse block to a piece of test gear 
sitting near-by.
My TS-850 will not power up either; fuse condition unknown at this time; 
same deal; connected to 12VDC but no antennas.
The stroke took out my computer, my ISDN router, computer monitor, video 
card, network card, network hub, my wife's computer video card, the surge 
suppressor on my wife's computer, who knows what else, as I am still 
investigating. There were breakers opened in the breaker box in the house 
and in my work shop; the stroke took out the stereo in the shop as well. 
There are surge arrestors on all the computer gear, plus two of the power 
company issued arrestors on the main panel.
My 12VDC system is derived from an external battery pack which also 
supplies my computer UPS. I think the surge came in on the house power 
lines and found ground through the 12VDC system and radios. The UPS is the 
only common component between the computers and the radios, due to the 
12VDC system. Perhaps I should break that up & have a separate 12VDC system 
for the ham gear, but it still would be connected to AC mains at some 
point. (Enter solar and wind system to power the shack).

>I practice good hygiene and usually have the PL-259s (and all the AC, 
>phone lines, LAN cables) disconnected at my station.

I wasn't that thorough...should have been.

>  However, the antenna/rotator/etc. wires still pass through something (a 
> window or a wall) and enter the house.

Same deal here.

>  It is at that point one has allowed  "lightning" (or its effects) to 
> enter and somehow at or near that point it should be dealt with - enter 
> the SPG.

I agree.


>Mike N2MG
>
>
>_______________________________________________
>Self Supporting Towers, Wireless Weather Stations, see web site: 
>http://www.mscomputer.com
>Call 888-333-9041 to place your order, mention you saw this ad and take an 
>additional 5 percent off
>any weather station price.
>_______________________________________________
>Towertalk mailing list
>Towertalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk

Thanks,
Robin Midgett KB4IDC
615-477-8976 cellular
615-322-5836 office
615-773-4198 home
rmidgett@bellsouth.net
robin.midgett@vanderbilt.edu