concrete. Doing so will allow surge energy to enter the shack and find a ground path through your equipment to the floor. Insulate your equipment with material that does not absorb water. Wood is not a good choice. Polypropylene is better than nylon to use as a full footprint sheet insulator. Obviously, you should not be on the concrete floor touching the equipment when a storm is near!

The first floor is the next best location. The magnetic shielding is less than the basement and the inductance to ground is higher than the basement. If your tower is close to the building, the recommended grounding strap, running down the outside wall, may inductively couple some energy from the tower. This is also true for other lines such as coax, tower lights and rotor lines. The longer this parallel run, the more energy will be coupled.

Our recommendation is to protect these lines at the tower base then run them in EMT (electrical metal tubing) steel conduit. The conduit should be grounded to the tower base ground point. This will act as a faraday shield for the cables inside. Do not run unprotected lines in the EMT. The protectors must be grounded to each other as well as to the tower ground. The best way to do this is to place the protectors inside a weatherized NEMA type box. A NEMA 3R or 4X will do nicely. Make sure the box is grounded, as well as the inside mounting plate.

To do this correctly, remove the paint from the box’ s outside and inside surfaces at the ground point and use proper joint compounds to weatherize the connections. Stainless hardware may be used. Crimp lugs must be crimped, soldered and weather covered. Solder (60/40) will not hold up to sunlight and ozone without protection.

Use a short section of strap to bond between the inside surface of the box and the inside protector mounting plate.

Our definition of a high-rise building is different than the upper stories of a house. The antennas on a high-rise are not on a ground mounted tower, but are usually attached to the building structure. Therefore, a single point grounding plan is a must for a high-rise equipment room. Grounding both the antenna and the single point ground connection in the equipment room is easy for buildings with structural steel frames - just bond to the building steel. Buildings other than steel construction are not as simple. Some high-rise buildings have a fire riser with a straight run to the basement where a super charger pump is usually connected. The riser may be used as a ground path if the pump’ s power is protected (3 phase) and a strap jumper installed to take the strike energy past the pump’ s gasket on both its input and output ports. If the riser is over 50 feet away, it may not be the best ground path to use. Check for other paths such as existing building lightning rods with down conductors or large electrical conduits. Do not use drain pipes or vent stacks. If none are available, regardless of the path distance, and it is impossible to run a strap down the side of the building, then the antenna just can’ t be grounded! When an ungrounded antenna is hit by lightning, the energy will traverse the coax line to your single point equipment ground location. This may be many meters from earth and the inductance/resistance voltage drop will be very large (hundreds of thousands of volts).

The ideal plan is a single point ground with no sneak paths. Sneak paths are loops that allow lightning current to flow into the equipment room. The easiest sneak paths to miss are the safety ground and the concrete floor (discussed above). The safety ground can be fixed by adding a distribution panel and protector at the single point ground location or, for small sites, a plug-in protector grounded on the single point ground panel. All l/O’ s (input/output) must be protected at this single point. The next thing to measure is distance. During a strike, distance equates to voltage drop to earth, the entire room of equipment will be elevated. The 

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