Amateur Radio and Lightning Protection

By Dave Land KD5FXApr. 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/Surge/RF-Lightning-Protection

Equipment Damage-Alpha Delta also makes good equipment for this…http://www.alphadeltacom.com/

This drawing is a summary

Radio

Power Supply

Coax Surge Protector

AC Surge Protector

Ground Buss Bar

To antenna, coil coax once inside the house, ~90 deg corners, go DOWN justbefore the coax goes outside

PC

To ground, heavy gauge, no sharp turns,go DOWN, no coils of wire

Ethernet Surge Protector

Grounded Antenna Switch

To AC Supply