Shield Your Helium Hotspot From Powerful Lightning Strikes

How do you attach a light­ning arrestor to your Heli­um hotspot anten­na? What does one look like? Is it dangerous?

Let’s start with a pic­ture. This will answer 90% of your questions.

You can (and accord­ing to knowl­edgable ham radio oper­a­tors) SHOULD con­nect the light­ning arrestor at the oth­er end of the cable, down by the min­er. Anoth­er way of say­ing that is: Don’t attach the light­ning arrestor direct­ly to the anten­na like you see in the pic­ture, attach it to a short piece of cable that con­nects to the min­er, and a long run of cable that goes to the anten­na. That did­n’t fit into my pic­ture, so I did it this way.

Now, let’s talk about what you can expect a light­ning arrestor to do. Hint: Despite the blog post title, a light­ning arrestor won’t stop a bolt of lightning.

A light­ning arrestor con­nects the anten­na to the anten­na cable. It pass­es the RF sig­nal from one to the oth­er through a medi­um that, when it gets too much pow­er, it breaks, just like a fuse. RF engi­neers will prob­a­bly lose their minds when they hear it explained that way; they’ll start spout­ing about ion­ized gasses and fixed gas dis­charge tubes and input/output surge mag­ni­tudes. They’re right, but you don’t have to know all that to use a light­ning arrestor. 

A light­ning arrestor will NOT stop a direct light­ning strike. That would anni­hi­late your house. While it would be awe­some adver­tis­ing to see a pris­tine hotspot mirac­u­lous­ly pro­tect­ed in the mid­dle of a charred and black­ened house hit by light­ning, it would­n’t be true.

All a light­ning arrestor real­ly does is pro­tect your elec­tron­ics against the sta­t­ic elec­tric­i­ty that can build up dur­ing a storm. If the ener­gy feed­ing into your anten­na (don’t kill me light­ning sci­en­tists!) gets too high it zaps the gas in the mid­dle of the arrestor, break­ing the con­nec­tion to the anten­na cable, and all the ener­gy is divert­ed to that ground wire (which is hope­ful­ly attached to your house ground.)

So, uh, how does it work? Just screw the thing in between your anten­na and anten­na cable, con­nect the attached ground­ing wire to a met­al “path” that goes all the way to the ground and you’re done. 

Wait, you want more? What anten­na is that? Where did I get that mount? What’s the inser­tion loss on this light­ning arrestor (make sure you get the right con­nec­tors!) vs the stuff the mil­i­tary uses when they don’t want to fritz out a $40,000 piece of elec­tron­ics? Psst, just get one from McGill that fits your cables.

I’ll start with the anten­na. I don’t know what it is. A friend brought it over. He said he’d bought it on eBay and what did I think of it? I thought it would make a good demo for this light­ning arrestor post, so I just gave him a Near­son 8 dBi I had lay­ing around and kept his unknown anten­na, which had the only thing that mat­tered: An N‑connector on the bottom.

What about the mount? Made that out of alu­minum bar, twist­ed, drilled, and ground to fit. Should’ve drilled first, but I made it work. The oth­er super cool part of this project is the use of rivnuts. Stop here if you want to learn any­thing more about light­ning arrestors, and refer to the above picture.

Just because I love build­ing stuff and shar­ing knowl­edge, here’s the jour­ney. I start­ed by clamp­ing the alu­minum bar in my vise, then twist­ing one end 90 degrees. 

Twist com­plete. Noth­ing fan­cy, just sim­ple and func­tion­al. I’ll leave that pink paint on the end of the bar. Pink means you like to party.

Then I drilled out the holes I’d need for the anten­na mounts and the pole mount. 

I love that drill press. A ran­dom guy gave it to me. I saw it in his garage and com­ment­ed on how old and rad and heavy duty it was. He said, “That thing’s dan­ger­ous, I watched my grand­fa­ther lose the end of his fin­ger in it. Do you want it?” Yep.

It weighs about as much as I do. I love heavy metal.

Next, I laid out what I’d need. Anten­na, light­ning arrestor, ground­ing wire, easy dis­con­nect ter­mi­nals, and a rivnut. Aw yeah, rivnuts!

Ok, what’s a rivnut? 

It’s a cool lit­tle way to add a nut into a thin walled piece of met­al. You drill out the hole, screw the nut onto a rivnut tool, insert the sleeve into the hole, then com­press the sleeve of the nut, secur­ing it to the wall of the pole.

Here’s what it looks like. That’s ready for a 10–24 bolt, which I hap­pen to have a bunch of.

I used a u‑bolt to clamp on my demon­stra­tion anten­na mount.

Then I had to make the ground­ing wire. I used 12 gauge cable for this demo, most specs require 10 or 12 ga. You need to crimp on quick con­nect ter­mi­nals to both sides, then seal the heat shrink around ’em. Here’s what it looks like with the wire stripped, before I made the connection.

Here’s what it looks like once you crimp it.

I crimped both sides, used a heat gun (Steinel HL2020E if you must know) to shrink it down all tight and pret­ty, and I had my ground­ing wire. You want these to be as short as possible.

All that was left was to con­nect every­thing up. Here’s what it looks like with­out a bunch of words past­ed in. Yes, I could’ve made the ground­ing cable short­er. I just didn’t.

Pret­ty sim­ple, right?

Oh, and the inser­tion loss? Let’s be mean and call it .5 dB. If you’re deploy­ing for a crit­i­cal appli­ca­tion and want to drop $150 on a badass Nex­Tek Surge Guard light­ning arrestor with < .1 dB loss, you can do that because every tenth of a dB counts. But.…you don’t have to.

Ok, that wraps up light­ning pro­tec­tors. You don’t need to do any of the building/light fab work I did, you can just screw it into your anten­na and use the mount that comes with any decent anten­na. It’s sim­ple. You got this!