Proper way to disconnect a station for thunderstorm.

[srd]

Hi,

I am trying to understand a bit about lightening protection, specifically, what is the proper way to disconnect an antenna from station equipment? I am currently working the grounding and bonding of the station, and have LMR400 going to an SPGP on the exterior wall where, as I understand it, I need to put in an arrestor which connects the "unprotected" side to the station "protected" side.

What I don't get is, should I have to open up the panel each time a thunderstorm comes and unscrew the LMR400 from the arrestor at that point? Aside from being tedious, seems like I would wear out the threads and thought there must be a better way.

Thanks,

 

[Crawdad]

No, you don't have to but replacing a worn out PL259, it seems to me, is a hell of a lot cheaper and easier than replacing radios, tuners, power supplies and anything else in your shack that can get cooked. Myself, I disconnect the coax that runs into the shack leaving my HexBeam connected to ground via the ground wire/rod. So far so good after a busy lightning season this past summer. I also disconnect the rotator control cable on both ends. It all takes just a couple minutes and hopefully protects my investment as much as possible. My $0.02

7 3

 

[ClaimJumper]

Yeah. That's probably the safest thing to do. Disconnect is best. I've heard tell of people putting the end of the coax in a glass jar, and leaving it in the shack. I made my shack with an easy to pull through conduit just for that reason.

 

[brandon7861]

Here I go again. I just wanted to add my $0.02 on glass jars.

IMO, a glass jar is only good for the charge that builds up between the center conductor and shield. That might be ok for a nearby strike or charge buildup from a passing storm, but for a direct strike without a tower ground or other grounding setup (like if you had a dipole in a tree with no grounded lightning arrestor where it enters your house), having the coax in a glass jar would absolutely terrify me. To a mile long lightning bolt, a glass jar is nothing. The arc will simply jump out of that jar and find the nearest ground, and when it does, chances are that jar shatters sending glass everywhere. If your antenna setup is ungrounded, a glass jar is not just false comfort, it's potential shrapnel. Some form of outside grounding is a must!

To my knowledge, good lightning arrestors fire at a voltage just over their rated RF voltage. Lets say an arrestor is rated at 200w RF. Sqrt(200w*50Ω)=100v RMS or 142v peak. Even if it were designed to fire at that exact voltage, that's still enough to kill a radio's front end in receive.

The best protection is lightning rods, several of them, on a good ground network. Take away lightnings chance to strike in the first place. My antenna is 60' lower than the highest point in MN and I have never had a lightning strike. It strikes all around us, but not there. We have three lightning rods all tied into a ground network of 3 ground rods around the cabin. The tower has its own ground too, and thanks to my base loaded sirio827 also being at DC ground potential, the radials and antenna tip can also serve as lightning rods dissipating charge before it can build up to the point of a strike. Lightning rods are not a guaranteed solution, but they sure do shift the odds in your favor.

If your tower and coax shield are grounded, then by all means, save the money on the arrestor and just use the jar. But if your antenna is in a tree, best to do something else.