Amateur Radio and
Lightning Protection
By Dave Land KD5FX
Apr. 2013
Topics we’ll cover:
What is lightning?
How can we protect our Ham Gear?
Example Drawings
What is lightning?
-It is a complex AC surge with a typical
frequency of around 20 to 500 Khz.
-It is NOT DC!
-The IEEE Standard Strike is defined as a
8us Rise Time by a 20 us Fall time.
(That’s 50 to 125 Khz)
-Average Current is 18,000 Amps for the
first stroke and half that for the 2nd and
3rd strokes
-Average Strike is 3 or 4 Strokes
What is lightning?
-Does Lightning ever strike the same
place twice?
-Of course! Ever lived near a tall
building or a tall radio tower?
-The Strike Frequency goes up as the
square of the height over average
terrain.
-NOTHING can be done to prevent a
strike.
What is lightning?
-50% of all strikes have a 1st strike of
at least 18,000 amps!
-10% will exceed 65,000 amps
-1% will exceed 140,000 amps!
-The largest on record was about
400,000 amps!
Equipment Damage
-Power Line surges are the greatest
source of damage to electrical and
electronic equipment.
Equipment Damage
-Power Line surges have four basic
sources
-Lightning
-Local Utility problems
-Your Neighbors
-Your own equipment
Lightning is the Greatest Normal Threat
to your gear.
Equipment Damage
-Damage caused by lightning
-Destruction Due to the
Lightning Bolt
-Exposure to the Stroke Channel
-Heating Effect of the Lightning
Strike
Equipment Damage
-Secondary Effects
-Electromagnetic Pulse
-Electrostatic Pulse
-Earth Currents
Equipment Damage
-What can you do about it?
-Give lightning a LOW impedance
path to ground
-Give it a HIGH impedance path to
your equipment!
-You MUST have a GOOD ground
Equipment Damage
-Give lightning a LOW impedance
path to ground
-LOW Impedance is:
-Short
-Fat
-Straight
-Clear
-Horizontal or down (lightning does
NOT go up!)
Equipment Damage
-Give it a HIGH impedance path to
your equipment!
-HIGH impedance is:
-Long
-Skinny
-Coiled
-Upward
Equipment Damage
-You MUST have a GOOD ground
-A GOOD Ground is:
-HEAVY gauge wire (No. 6 or bigger)
-Smooth turns in the wires
-All equipment connected to a
SINGLE point (do not daisy chain!)
-Avoid cold water pipes
-Don’t run ground wire UP!
Equipment Damage
-A distant strike can also come in on
Power lines, telephone and ethernet
lines.
-ALL these lines should have a GOOD
QUALITY surge protector on them.
-Polyphaser makes some of the best
surge protectors, expensive but it’s what
the PROS use for a reason.
http://www.protectiongroup.com/S
urge/RF-Lightning-Protection
Equipment Damage
-Alpha Delta also makes good
equipment for this…
http://www.alphadeltacom.com/
This
drawing is
a summary
Grounded Antenna Switch
Radio
Coax Surge Protector
Power Supply
Ground Buss Bar
To antenna, coil coax once inside the
house, ~90 deg corners, go DOWN just
before the coax goes outside
To ground, heavy gauge, no sharp turns,
go DOWN, no coils of wire
PC
AC Surge Protector
To AC Supply
Ethernet Surge Protector