LIGHTNING PROTECTION SUBSYSTEM

The Problem

    Because the N3RR station is designed to be a top-ten, single-op assisted station and also be a PacketCluster node serving southern Montgomery County, MD and northern Fairfax County, VA, the design of the station must include provisions to keep the station on the air, even during lightning storms. So, I undertook to design the station so that all equipment inside the shack is always hooked-up to its AC power and its antenna(s). I have never suffered from a lightning hit with this design.

    I did suffer a hit to the Ring Rotor control boxes during the time I was re-configuring them and failed to ground them properly. As a result of leaving them unattached to my single-point-ground (SPG), I needed to replace a Zener diode in three of the units. (More on how to ground these units later.)

    So, my requirement was to achieve operational capability of my station, 24 x 7 x 365, even in the face of lightning.

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    Sub-system Considerations

    There are several individual items of an amateur radio station that must be considered when designing a lightning protection system:

    Personnel in the shack The Ham Shack/house Electronic equipment in the shack (TX, RX, AMPS, PCs, and the like) Electronic and Electrical equipment elsewhere in the house Rotors and their controllers Antennas Tower-mounted relay switchers Tower

    Each of these items was considered essential to the overall operation of the N3RR station and, therefore, the final lightning protection design included protection for all of them.

    Lightning Protection Design Overview

    I utilized several resources in determining what system of grounding to include in my ligntning protection system. First and formost, I abided by all of the specifications in
    ANSI/TIA/EIA-222-E in effect at the time I implemented my system, 1994. (The current specification is "-F-1996")

    Nearly all of the lightning protection design I used was derived from Polyphaser Corporation. There is a tutorial provided by Polyphaser that is very informative. Since Polyphaser provides so much reference material, I will not go into the theory of operation of my ligntning protection design, but rather, this Webpage will present the design I implemented.

    The Ground Grid

    Central to any lightning protection system is the grounding system, or ground grid, to which is attached the lightning protection elements and to which all ground busses/wires are attached. Pictorially, here is the ground grid system I implemented at the N3RR QTH.

    The distance from the 52 ft tower to the house is approximately 60 feet.

    I used a combination of CadWelding, Andrew Corporation components, and
    Polyphaser 1.5 inch copper strap with SS-30 anti-seize compound from Jet Lube to affect the ground connections.

    Also, I used 8 foot copper-clad ground rods with 16 foot spacing between them. I used Andrew Angle Adaptor Kit Type 31768A (Andrew Catalog 38, Page 600) to attach the ground wire to each tower leg and each guy anchor. Both of my towers have angle legs, not tubular. Polyphaser has interface products that will allow the attachment of copper straps/wire to galvanized steel tubular tower legs.

    Coax Cable Lightning Protection

    Pictorially, here is the ground system with hyper links showing the junction boxes at each tower and the Single Point Ground (SPG) at the house. Click on each hyperlink to view each of the junction boxes.

    134 foot Tower Junction Box - This box is a Hoffman box model A-242408LP.

    Here is the detail: 1, 2, 3, 4, 5, 6

    Note in #3 that I am using 11 Polyphaser DC-Block, bulkhead lightning protectors (one spare - for expansion) (model IS-B50HN-CO*), appropriate for the frequency band/power level needed.

    Note in #4, I am using four Polyphaser IS-RCT* 8-conductor rotor cable lightning protectors. These are used to protect five 4-cable Ring Rotors and a 4-cable relay switcher for the EF-180C 80M dipole. This relay switcher selects each of three pairs of coils in series with the 80M dipole to move it from CW to SSB in 8 possible overlapping band segments which cover 3.5 to 3.95 MHz.

    Note in #5, the positioning of an Andrew Ground Kit, Model# 204989-1 on the 1/2 inch LDF4-50A coax (forground).

    Note in #6, the connection of the ground kit ground wire directly to the tower.

    Note that the Andrew Ground Kits referenced here may be found on pp 609-610 of Andrew catalog #38.

    All coax cables are grounded at the top of the tower (near the antenna) and at the bottom of the tower (at the junction box at the base of the tower).

    In addition, each of the control wires of the topmost Ring Rotor and the EF-180C relay switches is connected to the tower (ground) through 115 Volt MOVs at/near where they are connected to the device.

    Adding a Ground Kit to RG-8 Cables

    Here's how I attached the Andrew Ground kit to a RG-8 cable: 1, 2, 3, 4, 5

    At the conclusion of Step 5, wrap the entire connection with the electrical tape provided by Andrew and connect the cable-end of the kit to the tower ground.

    52 foot Tower Junction Box - This box is a Hoffman box model A-161608LP.

    Here is the detail: 1, 2, 3

    Note in #3 that I am using 4 Polyphaser IS-B50HN-CO* lightning protectors for the HF antennas. This photo was taken when I had only one HF antenna in operation on this tower. Notice the three spare IS-B50HN-CO protectors.

    Note in #3, I am also using a Polyphaser IS-RCT* 8-conductor rotor cable lightning protector for the HiGain/Telex HAM-IV rotor at the top of the tower.

     

    Single Point Ground (SPG) Junction Box at the House - This box is a Hoffman box model A-161208LP.

    Here is the detail: 1, 2, 3, 4

    Note in #2 that I am using a Polyphaser IS-B50HN-CO* lightning protectors for the VHF/UHF antenna I have mounted on my roof-top.

    Also in #2, See how all of the coax/hardline feedlines from the towers connect to bulkhead connectors at the single-point ground inside the box. There are spare feedthroughs as well. The 1.5 inch copper strap connects the SPG panel inside the shack to this SPG box on the outside of the house.

    Note in #3 and #4, I am using a Polyphaser lightning protector for the Beverage feedlines. These Polyphaser protectors are model # 092-1109H-B and were originally used to feed my EWE antennas with a pre-amp located at the EWE. The +12 Volt DC voltage feeds throught the Polyphaser to the EWE pre-amp and the equipment is protected from lightning voltages above +30 Volts and below -1 Volt.

    Single Point Ground (SPG) Panel in the Shack

    As shown in the hyperlink, all coax cables and the 1.5 inch copper strap from the SPG box on the house connect to the SPG panel in the shack where individual coax cables and ground cables connect and distribute their signals to equipment, switches, and other ground points.

    Electrical/Telephone/SPG Ground-Grid Interconnection

    As shown in this pictorial, is an additional hyperlink at the AC/TELCO panel in the house. As shown in the hyperlink, the 1.5 inch copper strap is connected to the main AC panel ground and is routed out of the basement window where it becomes a *continuous* run of copper strap forming the ground grid connecting the SPG/AC/TELCO grounds together on the OUTSIDE the house.

    Whole-House Lightning Protection

    Joslyn Model 1265-85 whole-house lightning protection device at the power panel (Shown during construction). With this whole-house lightning protection device, I am much more comfortable that high voltage AC and lightning will not destroy/harm sensitive electronics equipment at the N3RR QTH (Ham and non-Ham equipment).

* Catalog-cuts reproduced with permission of Polyphaser Corporation.

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