Lightning is a random event that cannot be predicted or prevented. While most lightning strike victims survive, advanced planning through risk management is important for safety. Lightning forms when differences in electric potential in air volumes exceed thresholds, causing currents between charged areas. Protection strategies aim to safely direct lightning currents to ground via lightning rods or antennas, while also protecting equipment from secondary effects. Tactics include proper grounding of antennas and cables at multiple points, using surge arrestors and capacitors, and ensuring all equipment is bonded to prevent potential differences.

1. HAM Radio Lightning Protection
Literature Study
&
Practical Thoughts

2. „Silly“ Questions
• Is a lightning AC or DC?
• What‘s the voltage of a lightning?
• Why do I sometimes hear a thunder and
sometimes not?

3. Lightning Protection
• Lightning is a capricious and random
event. It cannot be predicted with any
accuracy. It cannot be prevented.
Advanced planning in the form of a risk
management program is the best
defense for maximum safety.
• Eighty percent of lightning strike victims
survive the shock (movie 50,000V accident)
taken from www.lightningsafety.com

4. How does a lightning work? (1/5)
humid air = N2 + O2 + H2O
is an extremely good insulator:
Polarization in an air volume +
movements of air volumes against
each other create a frictional
separation of electrical charges
+ +
+ - - - - -

5. How does a lightning work? (2/5)
.
+ +
+
- - - - -
There is a difference in electric potential in separated volumes of
the air. If voltage is too high (>10-30 kV/m), then an electrical
current occurs either between two areas of different polarity or
between a charged area and ground. A lightning can be seen when
the current transforms the air into plasma.
This was close
but 9V1MS was
not hit this time
Step leader
streamer

6. How does a lightning work? (3/5)
1. Leader departs cloud in steps of 1 µs duration.
2. Length of leader is in tens of meters.
3. Pause time between steps is 20-50 us.
4. A fully developed leader can lower 10 coulombs or more of
charge! Q= C*U = 10,000 µF * 1,000V
5. Downward speed of propagation is ~ 2 X 10^5 m/s
6. Average leader current is about 100-1000A.
7. Leader step peak pulse currents are at least 1 kA.
8. Leader pauses produce other downward branches.
9. Potential difference between the leader and the earth is in
excess of 10^7 V = 10 million Volts.
10. Breakdown occurs in excess of 10^7 V and streamers move
to the leader.
Taken from „Lightning Rods: Recent Investigations“ section 5.4.2 of www.lightningsafety.com

7. How does a lightning work? (4/5)
.
1. A lightning is a constant current source. Once the lightning
path has been formed (100-1,000 A) , there will be a sufficiently
high voltage being built up in order to maintain the lightning
current. (10,000 – 200,000 A). Note: Essentially no insulation
helps against a lightning.
2. A lightning is a HF phenomenon with a maximum power at
about 0.1- 1 MHz (1µs pulse + 2-50µs pause per step).
Note: due to the skin effect, a direct hit lightning travels in the
shielding of a coax cable
3. A lightning produces a magnetic field which causes electro-
magnetic secondary effects
Note: induced voltages by secondary effect cause 99% of the
common lightning damages

8. How does a lightning work? (5/5)
.
-A ground lightning produces a voltage spike which lifts a whole
area up to voltages of 150+ kV against ground
-lightning dissipation theory: a lightning rod on a building
prevents the lightning strike by providing a conductive pathway
between the statically charged cloud and the lightning rod. Static
charges gradually migrate along this pathway to the ground, thus
reducing the likelihood of a sudden and explosive discharge
- lightning diversion theory. a lighting rod protects a building
by providing a conductive pathway of the charge to the Earth.
The sudden discharge from the cloud would be drawn towards the
elevated lightning rod but safely directed to the Earth, thus
preventing damage from occurring to the building.

9. Example (1/3) – Lightning in Singapore

10. Example (2/3) – Lightning in Singapore

11. Example (3/3) – Lightning in Singapore
a dangerous practice:
burying lightning protection
lines in a wall

12. Common misconceptions
1. 100% safe lightning protection is possible
2. Equipment must be kept totally clear from lightning effects for not
being damaged
3. A „floating antenna“ with no ground at all won‘t catch a lightning
(movie airplane strike + eham story)
4. Lightnings can be „caught“ by antennas (movie CNN tower)
5. Unplugging the antenna at reverse side of the radio during a
thunderstorm would prevent a damage of the equipment and
operator
6. The Diamond SP1000 etc. are good lightning protectors, just put
them into the cable, at about 1m after the antenna
7. An antenna which is located next to a higher building would not be
hit by a lightning: cone of protection myth (utility pole movie)

13. Lightning Protection Strategy
.
1. Protection against a direct hit into the shack
which prevents the death of the OP and prevents a fire hazard
2. Protection against secondary effects in the shack
which prevents the damage of equipment in the first place.
Seldom, secondary effects also lead to death of OP and to fire hazard
These two goals are often confused and therefore mixed up with
each other which leads to wrong designs.
Both goals must be kept in mind at the same time. It is not
suffcient to just address one single goal!

14. Tactical HAM protection against a Direct Hit
(1/2)
.
Goal
lead as much lightning energy as possible into the existing
lightning protection system, so that no lightning current enters
the shack (where it would fry the OP)
• You must ground antenna structure and antenna cable
shielding and rotor cable shielding already at rooftop and not
only at the shack
• You must ground antenna cable shielding + rotor cable
shielding a second time before the two cables enter the shack
• You should provide a possibility for easy disconnecting the
antenna + rotor cables and for grounding them at a point
before they enter the shack and you should use it when not operating

15. Tactical HAM protection against a Direct Hit
(2/2)
.
• use inductivities as a HF resistances immediately after
individual grounding points of the cable shieldings.
• cable coils are „bad“ inductivities, they will produce large
induced secondary effect voltages (see later)
• „Good“ inductivities for coax cables are ferrites (from old
computer monitors) and 90° cable bends
• Think about corrosion protection of the grounding points and
measure resistance of each grounding point frequently.
• Avoid stranded grounding wires for direct hit groundings
because of danger of explosion due to forces by induced
magnetic fields in each individual strand

16. Side effects and limitations of Tactical HAM
Protection Measures against a Direct Hit
.
• Reduced antenna sensitivity at low frequencies because
double grounded coax cable is an L/C high pass filter
• Cables are often not disconnected after use of the radio
equipment (lazyness, requirements of operation)
• OPs often do not notice thunderstorms during operation (e.g.
shack is in basement)

17. Tactical equipment protection against
secondary effects
.
Goals
a) avoid high potential differences between center lead and
shielding of antenna cables at radio antenna connector
b) avoid high potential differences between single wires of
the power supply cables
c) avoid high potential differences between different
equipment housings in the shack

18. Secondary effect protection (1/4)
.
• avoid high potential differences between center lead and
shielding of antenna cables at radio antenna connector
• Use „surge arrestors“ such as SP1000 just before the radio
antenna connector. Polyphaser surge arrestors (S$ 90.00) have
a better design than cheaper Diamond gear (S$ 25.00)
• Use DC blocking capacitors just before the radio antenna
connector

19. Secondary effect protection (2/4)
.
avoid high potential differences between single wires of the
power supply cables. best solution: disconnect each and every
single power supply cable from your shack after operation,
otherwise internal induction loops will occur
14.200
Inductive loop
Power line
Antenna cable
Lightning
current
Example for ground wires

20. Secondary effect protection (3/4)
.
avoid high potential differences between single wires of the
power supply cables: second best solution:
use commercial surge protectors in power lines
power distributors often have built-in surge protectors
this will not protect you fully against overvoltage in internal
circuitries

21. Secondary effect protection (4/4)
.
avoid high potential differences between different equipment
housings in the shack. All equipment housings in the shack must
be tied together electrically so that all points rise together in a
voltage spike and fall together with a voltage drop. Any
differential between any two points on the system and one may
get current and damage. No daisy chaining them or one may
provide a ground loop.

22. Side effects and limitations of Tactical HAM
Protection Measures against secondary effects
.
• Reduced RX signals because Voltage limiter/surge arrestors
have insertion loss of 0.3-0.6 dB
• Reduced TX energy because surge arrestors can be triggered
by TX energy
• Cables are often not disconnected after use of the radio
equipment (laziness, requirements of operation)

23. Still Unsolved Problems
The above measures apply when the radios can be
disconnected after operation.
More complicated measures are necessary if radio is operated
24/7. There is the danger of being surprised by a thunderstorm.
One cannot try out the measures. This is the largest drawback.
If the setup works, it can also work because one has a lucky day.
A fatal conceptional mistake or corrosion turns out only after
there has been a damage, which often includes death of OP

24. Example: lightning protection of RX/TX
equipment
(taken from the ICOM AH-4 ATU manual)

25. Worst mistakes
• Ignoring lightning problems: „I don‘t see the
problem, so it is not there“
• „everything is fb because nothing happened so
far“
• thinking that proper grounding of equipment is
intended for better reception (see also
www.eham.net/articles/21383 )
• Letting loose antenna cable float without
grounding the loose end at all

26. Ressources
• http://www.lightningsafety.com
• http://www.lightning.org
• http://www.struckbylightning.org/
• http://www.sirlinksalot.net/lightning.html
• http://www.polyphaser.com/ (look for the technical notes, they are good)
• www.youtube.com (search for „lightning“)
• www.eham.net/articles/13461

27. Hands-on Examples
• Kenwood TS-2000 manual