I've said part of this before, but that message didn't make the reflector: I
don't want to use the bandwidth, but I really do need to explain the layout
first.
The talk on ground systems and various back up methods started me thinking
about my system. As I've mentioned I have two stations/systems
*relatively* close: There are two main towers, the big one which tops out
with the UHF/VHF arrays at 130 feet and a little 32 footer with a multi-band
HF through 6-meter vertical and an antenna for the stereo at the back of the
shop. In addition there is a 20 foot mast on the north side of the shop
holding a duo-band 144/440 collinear vertical. All antennas run at DC
ground potential except for the half sloper on 160. The Antennas at the
shop are tied together with bare #2 copper cad welded to the ground rods at
the bases of the towers and masts. The ground also extends out into the
yard with more copper and ground rods, but it is a much smaller ground
system than the one for the big system. The big system ground consists of
roughly 600 feet of bare #2 copper cad welded to something on the order of
32 or 33 8' ground rods. The two ground systems run within about 20 feet of
each other directly north of the big tower. The shortest run for a common
house ground tying the house and system ground together is a direct line
from the bulkhead where the cables from the tower come in to the entrance
panel.
The computer system is on a gigabit network using CAT-5e cable which takes a
130-135 foot run from the switch in the den (next to the main station)to the
shop. The shop has a bare #2 cable that runs about 2/3rds of the
circumference. The interior of the shop is painted barn metal while the
exterior is vinyl siding so for RF purposes the building is pretty well
shielded. All coax feeds come into the shop through a common point near the
base of the tower on the west wall and are routed through inch and a half
steel conduit to within a couple feet of the rigs. The cat-5e comes in
through the base of the south wall, about 3 feet to the east of the station.
Unfortunately the shop and house run off separate electrical feeds (from the
same transformer) and the shop ground is surrounded by a sizeable chunk of
the concrete apron in front. That makes the ground rod unreachable for the
radio system ground except by bringing the ground cable through the south
wall and through conduit to the entrance panel. Unfortunately there are
doors in the way and the ground cable would have to run over at least one
door to get to the panel. However to complicate things all the equipment
uses three wire cords with grounds which do tie to the panel ground and the
station equipment is grounded to the outside system buss of bare #2 copper.
This indirectly ties the grounds back to the entrance ground. Not the best
choice but unavoidable.
Two of the computers and some times three can be interfaced with the rigs in
the shop and or house. That means I have two radio and computer systems on
different electrical feeds tied together with the network cable. I'd go
wireless but so far it's too slow. Way too slow to be practical in my
situation where the computer system runs 24 X 7 and has storage measured in
multiple terabytes. It is not unusual to be doing daily backups of several
hundred gigabytes across the network.
Virtually all of the equipment with the exception of the little Yaesu FT897d
backup rig and the old Hallicrafters station is on 24 X 7.
What I'm looking for are suggestions on the grounding system. Should the
two (shop and house) be tied together? What about the shop entrance ground
and the system ground? Any other socially acceptable suggestions?
Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|