Answers interspersed.
73, Pete N4ZR
The World Contest Station Database, at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at
reversebeacon.blogspot.com,
spots at telnet.reversebeacon.net, port 7000 and
arcluster.reversebeacon.net, port 7000
On 9/18/2012 10:46 AM, Dale Svetanoff wrote:
Pete,
Two questions: 1) That 40 feet of bare #2 wire between the entrance panel
and power line ground - I assume it is run outside, and if so, how many
ground rods are on it?
My shack is on the second floor - the wire runs along a first floor
porch roof and then down the side to the existing ground rod that also
serves the main electrical panel.
2) Does the wire provide all of the grounding for
the entrance panel, or do you have one or more ground rods tied to the
panel?
See above
While I understand and agree with your comment about non-ideal
installations, I think the point has to be made that trying to accomplish
as good of an installation as possible should be a prime goal of every
radio installation design. The two most important factors, in ANY case,
are: A) Keep the lightning current on the outside of your
shack/house/vehicle; B) Design for as low an impedance as possible between
the entrance panel and earth ground and between tower (or antenna support)
and ground. Naturally, net Z will be the total of Xsub-L + wire resistance
+ bonding resistance + earth coupling resistance. Net Z should be figured
for frequencies in the range of about 100 kHz to 10 MHz, the main spectral
distribution of lightning energy. (Yes, it extends upwards to nearly 100
MHz, but at greatly reduced energy levels.)
My shack location virtually assures that I cannot achieve a good-enough
installation so that I should count on it. My solution, which has
worked so far (including a direct hit on the tower) is to disconnect
everything at the entry panel.
The latter is essential during the strike because of the huge currents
during a strike. Since all of the station equipment is tied (bonded) to
the one ground system (or should be), the lower the net Z to ground means
the less voltage developed differentially between grounded connections and
power feeds, antenna inputs, and so forth. (This is in addition to the
common mode induced currents from a strike.) Keeping the lightning
current on the outside of the building is key to minimizing what I call the
"Kingsford Effect" (conversion of a building into a pile of charcoal) and
is usually handled well by a good entrance panel, well-grounded, and
equipped with protective devices for each and every I/O line used in the
station. I can personally vouch for the effectiveness of that approach.
I contend that disconnecting the cables is probably as good as you're
going to get in my situation.
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