This previous Summer, work was started on the Lightning Protection System at WQ4RP. The basic plan was to bond all antenna feedlines, control lines, and power cables to a common single point ground reference. That single point reference is a a KF7P entrance panel designed precisely for this purpose.
I contend that while it may not be possible to guarantee 100% immunity from a direct lightning strike to one’s tower, tower mounted antennas, typical backyard dipole, or associated feedline(s), it is entirely possible to substantially increase the odds that such a strike will have most of its energy dissipated in a protective grounding system well before it has a chance to get into your shack or radio equipment.
The copper strap exiting the lower left corner of the Single Point Entrance Panel (below) is clamped to a ground rod, which bonds the panel to the grounding system. The copper ground rod clamps may be obtained from KF7P. The large round access hole in the top left of the panel is for routing cables into the radio shack.
KF7P Single Point Ground Entry Panel
3-Way Cadweld Connection at Top of Rod and Ground Strap/Clamp Below
I contacted Chris, KF7P about the best way to waterproof the copper ground rod clamp that secures the copper strap to the ground rod, as the trench in which the ground rod resides was to be backfilled with dirt. I followed his three step advice as closely as possible. First, three coats of automotive undercoat compound were applied to the clamp, allowing each coat to dry before the next coat was applied. Second, rubber amalgamating electrical tape was securely wrapped around the clamp. Third, regular scotch 33 electrical tape was wrapped over the amalgamating tape.
Waterproofing Ground Strap to Ground Rod Connection outside WQ4RP Radio Shack
Over the past few months, additional coax, control lines, and power cables have been wired into the entrance panel. Every conductor that enters the radio shack passes through this panel.
KF7P Panel with Alpha Delta ATT3G50U Lightning Arrestors and Morgan M-348B Control Line Arrestor
Twenty-Nine ground rods (8′ x 5/8″) were hammer drilled into their respective trench locations on the map below.
The three black circles on the map denote the radio shack, the tower, and the 160M loop antenna support post.
The intent of this extensive grounding system is to ensure that the majority of the lightning energy is safely dissipated in the grounding system, and that there is minimal potential difference between any point in the protected zone during a lightning strike.
Solid copper ground wire (#4AWG) bonds each ground rod with the use of One-Shot Cadwelds. The cadwelding process uses a patented method to permanently bond copper wire to copper ground rods. I took a short video of one of my cadwelds firing off, which may be seen here.
Having never used Cadweld One-Shots before, it took me several failed attempts before I developed a reliable method for ensuring proper cadwelding. Here are some things I learned from the manufacturer’s brochures, internet research, and personal experience:
- Wear disposal plastic gloves to keep moisture from your hands from transferring to the ceramic mold.
- Lightly sand the copper surface of the ground rod where it comes into contact with the ceramic mold.
- Lightly sand the end of the copper wire(s) that are to be bonded to the ground rod.
- Clean the sanded areas on the ground rod and copper wire(s) with alcohol.
- After gently positioning the ceramic mold onto the ground rod, make sure there is no air space between the ground rod and the rubber grommet; If you can see daylight between the grommet and the rod, your molten material will leak out onto the ground. Keeping the ceramic mold as vertical as possible will help to ensure a good seal between the ground rod and the ceramic mold.
- When you insert the copper wires into the ceramic mold, make sure that the ends of the wires are touching the top of the ground rod.
- Also make sure that the ceramic mold is still as vertical as possible after inserting the wires into the mold.
- Most importantly, use a sparkler inserted into the hole in the top ceramic cap as a time delay igniter; This allows you to be a safe distance away from the action when the cadweld ignites.
As to point five above, during my final cadweld I was disappointed to observe that the grommet in the ceramic mold fit much too loosely onto the ground rod. What to do? I decided to try wrapping a small piece of one of my disposable gloves around the ground rod to supplement the loose fitting grommet. Would the cheap plastic glove keep the extremely hot molten material from leaking out of the mold? YES, that actually worked! I make no guarantees that this will work most times, but this method allowed me to complete the grounding system without having to purchase an additional ground rod.
One more point. My (well-known) supplier of Cadwelds shipped the individual cadwelds loosely packed, laying down in a box, despite the boxes being clearly marked this end up. As a result, 8 of my 29 ceramic forms arrived too broken to use. The supplier promptly sent eight replacements–loosely packed as before, but fortunately none arrived broken. I was concerned that the ignition material in the Cadweld vials might have migrated out of the bottom of the vials since the individual Cadweld boxes were sliding around in the oversized shipping boxes during transit. As it turned out, this was not an issue, and all Cadwelds ignited properly with the sparklers.
The next installment will cover how the grounding system ties into the tower and 160M vertical loop.