Originally Posted By: HerrStig
Inviting lighting to strike anything on the roof of a house is folly. A "lightning rod" is used to discharge the buildup of voltage which occurs when a highly charged cloud is close enough to the ground that the charge it contains could to jump to earth. The rod bleeds electrons into the void between the cloud and earth and causes the voltage difference to drop to a level such that a lightning arc can't jump.
Three fundamental inaccuracies. First is claiming a lightning rod does what the Early Streamer Emission industry claims. At one point, their claims were rejected by the NFPA. So ESE companies sued the NFPA to bankrupt that non-profit standards agency (who write the National Electrical code). NFPA used strategy to prove those ESE claims have no merits; have absolutely no basis in science. Bottom line statement was this: they should spend some money doing research rather than so much money only promoting bogus products.
A lightning rod works because it is the best conductor to earth. Lightning will strike whatever it decides is the best connection to distant earthborne charges. And so an ESE device on an FAA tower (a test of the technology) was struck and blown off the building in less than 3 days. Lightning found a best connection to earth - on a path that was insufficient for the current.
Lightning rods work because a hardwire is a better electrical connection to earth (compared to the structure). 'Whole house' protection works because earthing for every incoming wire (directly or via a 'whole house' protector) is a better electrical connection to earth (compared to household appliances). In every case, surge protection is always about connecting a direct lightning strike on a harmless (more conductive) path to earth. Then 20,000 amps creates a near zero voltage - no damage.
Second, an 18 AWG (10 amp lamp) wire can conduct up to 60,000 amps. A typical lightning strike is 20,000 amps. A 6 or 4 AWG wire is more than sufficient to conduct direct lightning strikes to earth without any wire damage. Since the current capacity of that 6 AWG wire is four times larger than an 18 AWG lamp cord.
Third, induced fields do not cause damage as prmoted in urban myths and without any numbers. For example, a direct lightning strike is only tens of feet from an antenna. An antenna is designed to maximize those fields on its cable connection to a radio. So an induce field creates thousands of volts on that antenna lead. An NE-2 glow lamp (also seen in lighted wall switches) is connected to that antenna lead. A less than 1 milliamp current through that NE-2 glow lamp means thousands of volts drops to tens. Energy created by induced fields is that trivial - made irrelevant by protection already inside every electronics appliance.
Routine is nearby strikes to wrist watches, cell phones, car radios, calculators, etc without damage. For example, a direct lightning strike (maybe 20,000 amps) was connected via a lightning rod to earth on a hardwire. Only four feet away from that hardwire was an IBM PC. PC did not even blink with 20,000 amps only feet away ... because those induced fields do not even cause software crashes ... let alone damage.
Dish must have its own earth ground. Connection from dish to interior electronics must enter at the service entrance so that that coax cable first connects less than 10 feet (low impedance) to single point earth ground. Both those grounds must exist.
Also useful is a lightning rod above the dish to create a 60 degree cone of protection below that properly earthed lightning rod. Then lightning will connect to earth via the rod; not via the dish.
