Interesting, I was going to take down my setup and
re-assemble it this weekend. One of the things I had
in mind was to cover each shelf with solid flat
copper. Over that I will place a sheet of heavy
glass.. The glass is simply because it is so easy to
clean and I can use unfinished plywood for the shelfs
without fancy finishing and sanding. A couple of
inches will remain bare at the back,to which my
equipment bolts straight to. Thought this might
provide some addition shielding between equipment on
seperate shelves, also. My operating bench sit's
against an outside wall, and runs right up to the
hinge edge of the door jamb. It is a simple matter to
run the copper off the talble edge, around and through
the door jamb, and three feet down the outside wall to
the main ground rod. Yes, this doies give me a small
amount of inductance because of the bend. The power
mains (buried lines, no poles in my neighborhood)the
TY cable (buried cable) phone lines (buried lines)all
enter the house a few feet from my station ground. I
have bonded all these together there also. At this
point, if lightning hits it hits. I do not have
enough invested in the station to get too crazy about
it. My concerns are as much about having a RF ground
system as anything. I have radials, also going
throughout the yard, off my station main gnd. I'm
just running flat top wires so my situatiion is not
like some others. Yes, I have discovered copper roof
flashing. At about 20 dollars a roll for 25 feet
(Home Depot), 1 foot wide, it's definitely a viable
supply. Makes great portable ground plane,
counterpoise, also. On voltage fed antennas such as
Bobtails, a few square feet of it work wonders, or it
can be cut into 2" or 6" strips and used as radials
for 1/4 verticals. I used a Bobtail beam with a couple
of 1'foot wide strips forming a cross and it really
loaded up nice and got out great, too. A 2" strip
rolls up to a very compact package for the field.
Particularly effective for a waterside set up , where
they can be rolled several down into the water. Field
Day anyone? I guess when you have a 1 ft. wide sheet
of copper for RF useage, it has the same useable
conducting area as if you rolled that one foot
circumference into about 4" inches wide. So it is
effectively the same RF conductor as a 4" dia. piece
of copper wire, yes? with lower inductance? Since RF
only utilizes the surface of a wire conductor.
--- "Dr. Gerald N. Johnson"
<geraldj@storm.weather.net> wrote:
> On Sat, 2006-05-06 at 09:37 -0700, Randy Russe3ll
> wrote:
> > Even if the #6 wire only connects other gnd rods
> to
> > the central ground, and is buried bare? Having a
> hard
> > time seeing the inductance problem, Running a two
> foot
> > wide strip of flat copper is a nice idea, but when
> you
> > eventually connect to your equipment, you still
> have a
> > conductor only as wide as the connection bolt.
> Should
> > I build my operating table out of a solid cast
> copper
> > block extending directly ten feet into the ground
> > below my shack, with a few hundred strips of flat
> > copper running in all directions from that? Bolt
> the
> > entire chassis of each radio to it and call it
> good?
> > Or would a faraday shield be of added benefit? Hi
> Hi
> >
> Yes to both the copper table and thee faraday
> shield, though as a
> practical matter covering a wooden table with a
> copper sheet works as
> good as the solid block because the rapid rise of
> lightning current
> tends to keep it very near the surface of any
> conductor. I've built such
> a bench for use making low level measurements in a
> lab surrounded by
> 100KW and 250 KW HF transmitters. There I soldered a
> 2" wide strip of
> copper at each equipment location and bolted it to
> the coax connector
> mounting on the test equipment. Then I ran
> everything from a Sola to
> reduce the effects of line voltage variations and
> was still annoyed by
> them.
>
> Inductance is a severe problem in keeping voltages
> low between pieces of
> apparatus hit by lightning and the 18" wide straps
> DO WORK to keep the
> voltage drops down. Wire of any practical size
> doesn't NOT WORK because
> its surface area is so much smaller and its
> inductance is much higher.
> The copper strap needs to connect the grounds and
> lightning protectors
> at the power and telephone service entrances as well
> as the antenna and
> radio equipment grounds. In commercial setups that
> do survive lightning,
> the radio building has that strap on all sides and
> all wires in and out
> of the building go through that strap. Where they
> shortcut the full
> strap, they regularly loose equipment to lightning.
> With Polyphemus and
> the wide strap, they don't loose equipment.
>
> You can't get the whole of the equipment and
> external power and phone
> line feeds to go to ground potential when the
> antenna is hit by
> lighting, but if you surround the equipment with a
> low enough inductance
> ground connection that connects all the elements you
> can keep the
> equipment at close enough to thee same potential to
> not be damaged. But
> shortcuts in the form of wire in that ground cage
> defeat its purpose.
> Maybe a ribbon of #6 a couple feet wide may work but
> flashing copper
> hasn't been all that much more expensive until
> recently.
>
> --
> 73, Jerry, K0CQ,
> All content copyright Dr. Gerald N. Johnson,
> electrical engineer
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|