Reply from the author........

Thank you for reading and commenting on the article. It is interesting to see the full range of response in just these three replies.

In some applications and industries, full antenna lightning protection is the norm.

However, there are many applications where prevailing more lax practices can sometimes be either "There is no defense against lightning...just get ready to fix things", or "I just have a small antenna, that is much lower that the tallest or overhead grounded metal structure, so lightning won't hit (damage) it."

This 1996 article was written in the emerging days of 802.11 (WiFi), as one example of the proliferation of smaller (higher frequency) outdoor antennas. This article shows that an antenna can receive significant transients, even if not directly struck. The 802.11 application has again proven the susceptibility and protectibility of antenna lead-ins, when subjected to the thousands of damaging transients during the installed lifetime (even if sometimes limited to 5k to 10kV by internal cable breakdown).

The most appropriate conclusions from this article should be: 1. Outdoor antennas, even if shielded from likely direct strikes, face thousands of indirect transient pulses. 2. Threat levels are somewhat predictable and within the capability of protection devices and good installation practices. 3. High availability or critical outdoor communication antennas and cables need protection.

Thanks again,

George M. Kauffman NexTek, Inc. Westford, MA

I did not find that white paper very useful. Lightning protection planning normally assumes a direct attachment, and multiples thereof. I have rarely seen anyone go to such great lengths to explain effects of only a nearby strike, which happen on the scale of thousands of times more often, and with little if any effect, to a protected system. At the least it should not be labeled or implied that antenna and coaxial design would consider only their assumptions. The authors also failed to mention that proper grounding of the tower and proper shield grounding of coaxial cable would prevent the need for such unrealistically robust protector equipment as theirs reasoning suggsst are required, especially for only a nearby-strike, were that somehow the only consideration. Surge protectors and connected equipment can survive multiple direct attachments and thousands of insults from nearby strikes before failure when properly installed. When equipotential systems reach overload from the inductive effects of the high energy/fast rise times oif a direct attachment, current division via adequately sized conductors is the next defense. The surge protector equipment is the last defense, and there is scarcely a shadow of the massive potential of the original attachment or its current left by that time. Coaxial cable can only deliver about 5500v potential before it ruptures and shorts to ground. Maintaining equipotentiual along coaxial runs with frequent references to earth maintain a much lower potential than that, Thanks to our courteous authors for their donated paper, but there seems little if any practical design information in the work.

Before I became a power distribution engineer for commercial and industrial buildings, I was a utility company engineer. During college, I worked for two broadcast stations. I have observed many lightning effects on all three jobs. While this paper presents a good theoretical discussion of the parameters involved, I have concluded that no method of lightning protection is 100% effective. Lightning is just too powerful. While good lightining arresters and surge protectors are necessary and helpful, the best defense is to provide good low-impedance grounding and bonding for all equipment that might be affected by a lightning strike. Even if the equipment is damaged by a high-intensity lightning strike, good grounding and bonding should minimize the risks to people and propery.