1. Protecting Your Shack
From
Lightning
(as best you can)
Hap Griffin WZ4O

3. Point of reference – 0 volts potential
Concept of “Ground”:
Point of reference – 0 volts potential
Circuit returns
Actual “Earth” ground
For lightning, actual Earth is the point of reference

4. Types of Grounding: Safety Grounding (NEC) – 60 Hz
RF Grounding – Frequencies in Use
Lightning Protection (Mitigation) – DC to RF
If #3 is implemented properly and fully, #’s 1 and 2 will likely be covered.

22. Surge Protection in Shack: Don’t scrimp here – avoid cheap units
Look for protection capacity in Joules: higher = better
Metal case with ground screw
Don’t rely on “Protected” light on cheap units
Rated at 3840 Joules
Rated at 300 Joules

23. UPS / Surge Protection in Shack:
Combines UPS / AVR and Surge Protection
Rated at 1200 watts
Rated at 2200 Joules

24. Multiple Ground Points vs Single Point Ground

25. In a physically distributed multiple ground system, tie EVERY conducting object together with LOW IMPEDANCE conductors to minimize voltage differences during a lightning strike (i.e fences, light posts, tower, etc).

33. Ufer Ground

34. Ufer Ground

36. Bring all cables to BOTTOM of tower and provide lightning path to ground AT THAT point

44. Bring all cables into building through a bulkhead grounded plate
Use coaxial and multi-line surge protectors AT THAT POINT
(NOT in the shack)

46. PolyPhaser – Block DC, internal gas tube
Alpha Delta – Pass DC, replaceable gas tube

47. Characteristics of Grounding Conductors:
Since we are dealing with lightning currents that have large RF components, we must think about LOW RF IMPEDANCE, not just low DC resistance.

48. Effects of Length of Conductors

49. Ground wire = #6 (4.11 mm diameter) Ground Wire Length = 20 feet
Example:
Frequency = 7 MHz
Ground wire = #6 (4.11 mm diameter)
Ground Wire Length = 20 feet
From online calculators:
The inductance of the ground wire (assuming it is straight) = 9490 nH
Inductive reactance at 7 MHz = 417 ohms
If ground wire approaches ¼ wavelength long, it is effectively not there at all.
¼ Wavelength =
80 mtrs – 60 Feet
40 mtrs – 40 Feet
20 mtrs – 20 Feet
15 mtrs – 11 feet
10 mtrs – 8 Feet

50. “Skin Effect” of Conductors

51. Use Conductors With Lots of Surface Area
Use Gentle Turns

55. “Cadwelding”

62. Use Coax Switches That Ground Inputs Not In Use and That Have a Ground All Inputs Position
= BAD

64. Summary:
Think in terms of propagation time
Think in terms of RF – low impedance paths to ground rather than just low resistance
Think of your entire facility – not just the shack
Damage comes from differences in potential (voltage) – tie EVERYTHING together with low impedance bonds

65. Questions?