AC Power

Ac power protectors are available in many shapes, capabilities, and method of connection.  Some caution should to be exercised in choosing your protector.  There are many rather inexpensive power line protectors on the market that are clearly not suitable for the type of protection needed here; independent of warranty or insurance claims.  Many of these protectors depend on the safety ground wire to carry away the surge energy.  While the safety ground may provide a dc path to ground, the size 14 AWG wire commonly used is too inductive with respect to the rise time of the currents (RF energy) that it must conduct to ground.  In addition, some low-end manufacturers who do provide in-line ac protectors use ferrite core wound inductors to maintain a small sleek physical appearance.  While this approach works well when the protection is merely handling power line noise; the inductor saturates under the massive current of a real strike and the benefit of the inductance disappears.  There are other issues to be wary about – plastic housing and printed circuit boards to name a few, these should be avoided where possible since they will most likely not hold up under real strike conditions when you need it most.

Since we are establishing a local zone of protection for the radio room, as opposed to the whole house or building, we need to choose an in-line ac power protector that matches our voltage and current requirements.  For most small to medium size operations, a single 120Vac protector with the capability of 15 or 20 amps will provide all of our ac power needs.  Each of the electronic items with an ac power line extending beyond the circle should be aggregated into a single line as long as it is comfortably with the maximum amperage of the selected protector (usually 15 or 20 amps).  Larger sites with high-power HF amplifiers or transmitter will most likely have a separate 120Vac or more likely 240Vac power circuit that will require a separate ac power protector. 

In some high-end stations it may be necessary to go to 100A or 200A in-line protectors.  While this level of protector will not be addressed here the theory is the same, just the mechanics are different.

If station ac is sent out to the tower for convenience, safety lighting, or to run motors (not the common antenna rotator), then that ac circuit must be separately protected as it leaves the radio room for the tower. 

Telephone

Telephone lines come in many flavors (operating voltages).  By far, the most common is the plain old telephone line (POTS).  This is a balanced line with a –48 V dc battery talk circuit and up to 140Vac ringing voltage.  Here an inline protector is the most effective type of protector.  For a single telephone line, the PolyPhaser model IS-SPTL is recommended; for two telephone lines use the model IS-DPTL.

Other protectors are available for different line characteristics.  Again, the theory is the same; the protector is selected to match the electrical characteristics of the interface being protected and is mounted in common with all of the other protectors.

Caution.  Many of the protectors on the market use modular connectors (RJ-11, 12, 45).  While this is a great convenience for the installer, we need to recognize that electrically this is a very fragile connector and that any decent amount of surge energy is very likely to destroy the connector by welding it or fusing it open.  In addition, there are also the issues regarding the use of flammable plastic housings, too small and too inductive ground wire, and the use of printed circuit boards that can arc over to the equipment side.