The tower itself should be well grounded. The following url
http://www.3starinc.com/rohn_r-bgk2ggx_tower_base_ground_kit.html
shows Rohn's suggestion with excellent information. Their kit lists at
$170 & you should use 1 per tower leg. I found them last year at Hill
Radio for less than half that cost when I put up 100' of Rohn 55.
http://www.hillradio.net/
The kit includes 1 10' ground rod & 30 ' of cable with clamps. You should
use at least 1 or 2 more ground rods on each cable running radially from
the tower. ( I couldn't go 30' in the one direction so that cable makes a
big sweeping turn.) The rod & connection are buried. Use lots of
anti-corrosion compound . I like the marine-grade stuff sold for antenna
assembly. I also sleeve the connection with a piece of 4" or 5" PVC about
a foot long. Slot it to pass the cables, set it down over the rod &
connection. Then put an end cap on it at ground level. When you do your
annual tower inspection, it's a simple matter to remove the cap (I didn't
say glue it on - Hi), loosen, re-apply anti corrosion compound & retighten
the connection. The clamps included in the above kit are excellent. I
shudder when I see ground wire clamped to a tower with a hose clamp.
See Jim Brown & others information for bonding all this to all other
grounds.
Thanks for the bandwidth
73
Dave
WA3F
----- Original Message -----
From: "chacuff" <chacuff@cableone.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Tuesday, May 22, 2012 9:13:32 AM
Subject: Re: [TenTec] RFI Issues
Just my 2 cents worth....
Your grounding work shouldn't start just outside the wall from the radio
gear...it really should start at the tower and be an antenna/tower
grounding
"System" designed to stop/minimize the lightning impulse at its source as
you work back towards the station.
A single rod lightning protection system is of little protection because
much like Bob has pointed out the resistances involved between the
multiple
ground points there is also resistance between a single point of ground
and
earth. If the ground resistance was measured at the single rod it would
probably be measured as several hundred ohms. If your station lightning
protection ground was measured at that level and subjected to several
thousand amps of instantanous current simple ohms law will tell you what
kind of voltage potential you can expect on the chassis of equipment...and
that gets dumped onto the electrical system of your shack/house. Lots of
damage.
The lightning protection grounding has to be approached as a system. The
ground rods can be looked at like resistors...put more in parallel and you
bring the total system resistance down. That's done by driving multiple
rods at 2 times there length apart and bonding them together with large
gauge wire, preferrably bare. The Cellular industry uses #2 bare solid
(not
stranded) wire welded to the ground rods. It's not unusual to have a dozen
or more rods driven to get the system resistance down to 5 ohms or
less...the lower the better.
The tower should be tied to this ground "System" and all feedlines should
have ground kits installed on them which ties the shield to the ground
system. Each feedline and rotor cable should have an inline commercial
protection block...ie Polyphaser or ICE connected and tied to a common
point
with a low impedance path to the ground "System". Finally all this should
be tied to your house electrical panel at the point where your meter can
is
located which should be where the small ground rod the electrican drove
and
tied to the house panel.
As you can see this can get expensive (and complicated) but so can loosing
all your nice gear and a bunch of stuff in the house that's not related to
the ham shack. It can come to 10s of thousands of dollars easily....all in
a millisecond. Been there and done that. Hope to not have to deal with it
again.
Again just my 2 cents worth...
Cecil
K5DL
----- Original Message -----
From: "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
To: "Jim WA9YSD" <wa9ysd@yahoo.com>; "Discussion of Ten-Tec Equipment"
<tentec@contesting.com>
Sent: Tuesday, May 22, 2012 7:30 AM
Subject: Re: [TenTec] RFI Issues
Here's where I view that people get in trouble. They drive a ground or
two
and connect it to their radio or station equipment. They plug the radio
in
the wall plug which has neutral and ground. Neutral and ground are
connected at the breaker panel for the house per NEC. The ground at the
breaker panel is attached to a driven ground outside, again per NEC. A
lightning storm approaches and they disconnect their antennas. A nearby
strike, meaning up to 5 miles away, causes the two or more ground points
to
have different voltage potentials as they are separated by some distance
of
a few feet to several hundred feet. There is resistance in the earth
between the ground points thus with current flowing through the earth
there
is a difference in voltage between the two or more grounds. Now, what's
connected between the two ground points? The radio and station equipment.
Therefore, even when antennas are disconnected and the radio is turned
off
there is a path through the ground and neutral back through the radio or
station equipment. It spells failure and we often hear........"but my
radio
was grounded, my antennas were disconnected and the radio was turned
off".
The point is the fact that ALL grounds must be bonded together and
preferably outside of the structure. This includes a hard electrical
connection back to the AC mains ground point.
73
Bob, K4TAX
----- Original Message -----
From: "Jim WA9YSD" <wa9ysd@yahoo.com>
To: "TenTec .com" <tentec@contesting.com>
Sent: Tuesday, May 22, 2012 12:52 AM
Subject: Re: [TenTec] RFI Issues
Sorry Jim
When the FCC had checked out my installation cause of an RFI issue, they
found that I had a bad solder joint on my shielded ground and fixed it
for
me. All was well. If the the shielded ground was BS they would have told
me
and not fix it?
Tying station ground to electrical ground low impedance please describe.
Existing wiring. The 2 grounds were separated at time of inspection was
in
code then but is not in code now, residential wiring does not have to be
upgraded unless there was remodeling, house was sold, and the sort, so
then
it needs to be brought up to code at that time.
Stay on course, fight a good fight, and keep the faith. Jim K9TF/WA9YSD
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