[Top] [All Lists]

[Towertalk] Box forSPG and Lightning protectors

To: <>
Subject: [Towertalk] Box forSPG and Lightning protectors
From: (Robert Shohet)
Date: Thu, 19 Sep 2002 18:34:58 -0400
I think I can summarize the concepts in this discussion as follows:

1) Ground everything at the towers
1 1/2) Have polyphaser protection at the towers
1 3/4) Coil excess coax in a circle, lying flat
    at the base of the tower
2) Have a quality SPG OUTSIDE the shack
3) Connect the tower ground to the SPG
4) Connect the utility/telco ground to the SPG
4 1/2) Have additional polyphaser protection at the SPG OUTSIDE the shack.
5) Have ANOTHER ground panel INSIDE the shack for
    the coax/rotator cables coming from the outside and for the equipment
    ground (strap) at the operating position.  (Quick disconnects useful
from each other and from the INSIDE ground panel and
from the a/c outlets when not using them.

Yes, some would prefer to not disconnect things, but it really does help.
My towers having been hit 6 times last year and once this year, I can tell
that you reduce the likelihood of damage when everything is disconnected and
the metal
boxes can not touch each other.

7) There are many opinions on what to do and what not to do, some of which
based on scientific fact and some on myths and legends -  learn all you can
use common sense and REALIZE than no two itch's are the same and no two
are the same.  Ergo, there is no one universal concept of ground that will
work equally well
at all stations.  Overkill is the best way to go when designing a lightning


Bob KQ2M

----- Original Message -----
From: "KC2TN" <>
To: "'Jon Ogden'" <>; "'Tower Talk (mail list)'"
Sent: Thursday, September 19, 2002 6:03 PM
Subject: RE: [Towertalk] Box forSPG and Lightning protectors

> Not to disagree with Bill because he's been a BIG help to a lot of us here
> on this reflector (ME included) regarding station protection.
> BUT...
> I was confused about where to put my SPGP also ..My original design had it
> right outside the shack in an enclosure
> but I changed the design after reading the Ron and Roger Block QST
> "Lightning Protection" series "What Your Mother Never told you!.
> In that article there was this excerpt:
>      "...As we'll detail later on, the primary ground system is
> by a set of copper-clad ground rods, interconnected below grade, with bare
> copper radials. Also fundamental to a good protection scheme is the
> of a single point ground WITHIN the ham shack. This single point ground
> be used to MOUNT ALL of the I/O protection equipment and to provide a
> for all of the equipment cabinets at the station's operating position.
> INTERIOR single point ground is CONNECTED to the external ground system
> (composed of those radials and ground rods) by the lowest impedance copper
> strap that you can manage. The tower ground system outside and the single
> point ground system inside must be solidly interconnected with a low
> impedance metallic strap, so that your coax cable's shield is not the only
> interconnection conductor between these two ground points. Keeping as much
> of the lightning's energy off of the coax shield as possible is essential
> minimizing damage from a direct hit. For larger strikes, it's best to
> incorporate a grounding kit prior to the protector, to save your expensive
> coax connectors from arcing damage. An effective (good quality) coaxial
> in-line protector can then be used to handle smaller strike currents that
> may be tempted to travel down the cable itself."
> After conferring with Ron over lunch (he lives close by) we decided it was
> best to move the SPGP inside the shack
> to allow easier bonding of all the protection components, including an AC
> protector, to one plate. The plate was then
> connected to the EXTERIOR ground system via 2 6" copper straps. The reason
> for the two straps was to equal the total
> cross section of cable(s) entering (11") with the ground leaving (12") to
> attach to the exterior ground system.
> This keeps all voltages rising and falling together with zero current
> My exterior ground system consists of 2" strap cadwelded to 4 legs of
> radials off the tower consisting of
> 4 8' 5/8" ground rods 16' apart on each leg and also a perimeter ground
> connected to the AC panel all tied
> to the SPGP via the 2 6" straps.
> I should mention that my tower is only 10 feet from the shack and
> Electromagnetic Pulse protection is near impossible
> given the proximity of the tower. Unless I wanted to encase my shack in
> copper $$$$.
> BTW...This whole system did not come cheap! But the idea is to keep the
> energy in the ground field and most of it
> outside the house. Also, Ron's SPGP is in his closet next to his station.
> Joe - KC2TN

<Prev in Thread] Current Thread [Next in Thread>