[RFI] ISOBAR

[Pete Smith N4ZR]

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.