[PPRAANet] Surge Protector

Wed Jan 11 12:02:52 EST 2012

I have several of these. I have them mounted on all my ground rods (6) and
every antenna passes through these before entering the shack.
With all the lightning we get here in Colorado, the added protection is
important.

73
Rick W0RIC

MORE FROM Mike K6AER:

*Dissipation of Lightning Energy       *

*on Antennas and Towers*

* *

*by Mike Higgins - K6AER                              *

This short white paper is not intended to be a complete paper on the proper
surge suppression techniques but as an aid to understanding the issues in
considering the use and application of surge protection products with
antenna and tower systems.

*What is lightning?*

* *

The focus of this paper is Cloud to Ground lightning. First, a brief
overview of what a lightning strike is in order to understand what the
suppression issues are. Air movement and the friction of particles in
clouds create static electricity. This friction enables a positive charge
to build up until a discharge is inevitable and a potential path is
established with another cloud or earth. A strike leader will start to arc
skyward from a ground source until a discharge path is created from the
charged source (Cloud) and the discharged potential (Earth). The discharge
cloud to earth potential is complete when air molecules ionize and an
electrical path has been completed. With this, we have lightning. A
lightning strike is not a single strike but several strikes along the same
ionized path. Each strike is about 8-20us in length and will repeat in
numbers until the cloud potential is decreased and the ionized path is
lost. A lightning strike, although short in duration, contains millions of
volts, thousands of amps and has a great RF as well as a DC energy
component.

* *

*Why surge protectors?*

* *

The DC and RF component must be addressed in setting up a lightning
firewall suppression system. In commercial systems, the building has a
ground halo installed around the perimeter with an internal ground halo and
a suppression demarcation point for all outside wiring and coax entries.
Homes are built to a different standard and we must adapt where possible.
The often misunderstood NEC code for grounding is not applicable when you
are protecting your HAM radio equipment from external surge potential.
Grounding your equipment to the AC panel ground will not protect your
equipment from high current surges coupled on the antenna lines. This will
only prevents AC ground loops should you lose your primary AC return
ground. Because lightning has a great amount of RF contained in the strike,
any long ground leads will not ground off RF energy and at may best delay
grounding of DC spikes due to lead inductance. The best way to prevent RF
and DC surges from entering the Shack is at the cable entrance or at the
base of the tower. Each of these points can be considered a surge firewall
demarcation point. This ground point must be as short as possible. Even a
nearby strike can inductively and or capacitively couple thousands of volts
into your cable and coax system.

*Typical Installation*

* *

Let’s follow the proper grounding procedures from the antenna down to the
radio. The antenna lines should be grounded at the top of the tower when
possible. Should your tower be a crank-up, you will only be able to
effectively ground at the tower base. A fixed, guyed tower represents the
greatest conductor to ground. Running a ground wire up to the tower top,
although popular, is a waste of time unless the conductor is larger than
the tower or the tower is of the crank up variety. For guyed towers, all
guy points need to be grounded as well. Always place ground rods into the
soil around the tower and not through the concrete base. Each ground should
be at least twice the rod length in distance from the next ground rod. The
concrete of an ungrounded tower base will shatter when hit by lightning if
the base is not grounded. The tower should have at least three ground rods
spaced about eight feet out from the tower with connections to each leg of
the tower base.

Use copper or brass lugs when connecting to the tower base. Other metals
can cause corrosion on galvanized metal and can weaken the tower base.
Three would be a minimum number of rods in good conductive soil for a
ground halo. In poor soil such as in the mountains and in the western U.S.,
you might need more ground rods provide a good coupling to earth or the use
of a deep ground rod up to 40 feet. Use solid copper wire of at least 2
gage and connect all ground rods with brass or copper ground clamps. For
underground connections you will need to CAD Weld the copper connections.
All above ground connections should have a coat of Ox-Gard paste to
maintain the connection integrity with lugs and clamps.

The coax cables need to have their outer conductors grounded at the tower
base and attached to the tower ground halo system. At this point surge
protectors need to be installed in series with the coax lead before routing
antenna feeds into the home and to the radio equipment. It is best,
whenever possible, to protect the RF surge protectors from weather by
enclosing them in a NEMA or weather resistance box. If this is not possible
use a moisture protector barrier tape over the connections and surge
protectors.

The surge protection box would be the best location for all other surge
protectors such as those needed for Rotors, SteppIR Controllers and remote
control lines. The surge protectors should be attached to a mounting strip
with copper conductive (flat ribbon or cable) to the tower base ground halo
system.

Inside the radio room all coaxes should be attached to a grounded antenna
routing switch with a common grounding position for all entries. This
grounding location must be attached to the operating station grounding buss
bar. All coax and radio connections should be grounded at this point.
Remember we are also grounding RF energy as well as DC potential and long
ground runs are self defeating due to series inductance. A 33-foot ground
run will present a high impedance connection at 7 MHz during a lightning
strike. Use of a grounded antenna switch, will aid in radio isolation. All
radio equipment in the shack should be connected during periods of non use,
adding an extra layer of protection when connected to the ground copper
buss bar. This bus bar is your equipment demarcation point. Connections
should be made the outside halo ground system via a short #2 GA copper
ground cable or a flat ground strap.

All radio equipment in the shack should be connected to a to common ground
copper buss bar. This bus bar is connected to the outside halo ground
system via a short #2 GA copper ground cable.

 * *

* *

*Other Potential Sources*

* *

Many times radio amateurs will assume that a lightning strike came into the
radio room via the antenna connections. This may often not be the case.
Often electronic damage is via the phone, cable and especially AC lines in
search of a good ground. It is also imperative that surge protectors be
mounted on all entry conductors. In a typical home, AC mains, will only
have one ground rod. Though this may satisfy the NEC and local building
codes is not adequate for lightning surge grounding. Several ground rods
must be added for AC lightning protection. Your grounding solution and
protection will be only as good as the weakest link.

Many AC surge protectors are available to add to the AC panel to stop high
voltage surges from racing through the home wiring in search of the perfect
ground like your tower via your radio equipment. *In all cases, the tower
ground, station ground and the AC panel ground must me bonded together *with
at least a number 6 and preferably a number 2 solid copper wire.

* *

*Which Surge Protector?*

* *

The RMS voltage /wattage rating on a RF surge protector are as follows: 100
watts =70 volts, 500 watts=158 volts, 1000 watts=223 volts, 1500 watts =273
volts and 3000 watts=387 volts. If the break down voltage is too low you
will experience VSWR spikes on coax peak RF power. NextTek, ICS,
PolyPhaser, Hubner+Suhner* *are some of the manufacturers of RF surge
protectors.  You have to choose the proper voltage surge protector for your
working wattage.

Most rotor and controller line protectors can be a 35 volt MOV with a
parallel .01 capacitor 100V from each DC line to a common ground. These can
be bought commercially or you can make your own from over the counter
components. These components can be bought from Digi-Key, Mouser, Allied
and other distributers. Commercial units can be had from PolyPhaser, ICE
and others.

 ///

On Sun, Jan 8, 2012 at 9:07 PM, Virgil Yost <vwyost at comcast.net> wrote:

> Hi,  for Christmas I received a Alpha Delta Transi-Trap lightning surge
> protector.  Has anyone ever
>
> used one? Do they work?  Please send comments to Virgil  73  N0XRS  Thanks
>     n0xrs at arrl.net
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