Specifications

3.6 Lightning Protection Tips
!
Damage to the DAI-2 by lightning is not covered under warranty. See the complete warranty for more
information.
In most installations the DAI-2 is connected to both a telephone line and other broadcast equipment. Any equipment
in this situation is subject to severe abuse from lightning. In some installations this happens frequently. Lightning
can enter through the phone line, mistreat the DAI-2 and exit to the station ground system. It can also hit the tower,
elevate the entire ground system above ground by several kilovolts and exit through DAI-2 to ground. This is called a
"ground surge." In other words, the telephone line can hit the DAI-2 or the DAI-2 can hit the telephone line. The same
thing can happen with the power line.
3.6.1 Proper Ground System
The first step in any protection scheme is to install and maintain a high quality ground system. This will serve two
purposes. First, the intensity of the ground surge will be lowered because of the lower resistance to earth ground and
second, if everything is tied together with low impedance conductors, all equipment will stay closer to the same
electrical potential when the system ground takes a hit. All protection devices, equipment racks and transmitters
should be tied together with low impedance conductors, preferably copper strap, as short and as free from bends as
possible. Do not depend on metal conduit for ground connections. A properly designed and installed ground system
will pay for itself many times over in the damage it prevents.
3.6.2 Telephone Line Protection
Be sure your local telephone company has installed gas surge arrestors on your incoming telephone lines. Old
installations may contain carbon protectors which tend to provide less reliable protection. Be sure the ground
connection used by the telephone company is an integral part of your station ground system. Sometimes the
telephone company will use a nearby cold water pipe, metal conduit, or isolated ground rod for their ground and this
may be, electrically speaking, quite a distance from your station ground system. Do not disconnect their ground
connection, just add a supplemental conductor from their ground point to the station ground.
We highly recommend that you purchase and install your own telephone line surge protector in addition to the one
installed by the telephone company. Place this between the incoming telephone line and the DAI-2. These spike
protectors are designed to pick up a ground connection through the ground prong on a standard AC outlet so be sure
this is in fact connected to your station ground by the shortest possible means. For best result, install a "dummy" AC
outlet with no AC connections but with a short jumper from the ground terminal on the outlet the metal rack in which
the DAI-2 relay panel is mounted. Most protectors have internal, non-replaceable fuses which will blow during a
heavy surge. If this happens, replace the protector. Do not attempt to repair it.
DAI-2 Installation page 3. 7