How to reduce/mitigate the risk of lightning at the GPS outdoor antenna ?

[BravoV]

I'm just an "enthusiast", planning to install an outdoor antenna for my GPS antenna for my upcoming GPSDO, and I don't have the outdoor antenna yet. Currently I don't have any clue how to deal with the lightning strike ? 

Plan is to install at the similar location at the photo below, but at higher point near top of the roof (at the rakes/eaves ?) to get much wider view of the sky.


Image courtesy of kj7e from this Post
Click photo to enlarge.

How do you deal with yours especially the outdoor antenna for your GPSDO ?

[CopperCone]

Lol, you could setup a lighting probability detector that works on electrostatic fields and connect it to somethin like a hv relay to disconnect the antenna during these conditions..

they have coaxial products that would theoretically help against a strike, but I kinda doubt they are foolproof.

[BravoV]

Lol, you could setup a lighting probability detector that works on electrostatic fields and connect it to somethin like a hv relay to disconnect the antenna during these conditions..

they have coaxial products that would theoretically help against a strike, but I kinda doubt they are foolproof.

LOL, so what are you saying just keep prayin that the GPSDO, clock distributor, spectrum analyzer, freq. counter, scope and etc will be protected by The Almighty Thor god of lightning ? 

[CopperCone]

No I gave you a solution that gives you the best survivability but the highest downtime. People that work on antennas will probably have practical advise about the performance of inline protection products.

Can't really beat a disconnect and https://en.wikipedia.org/wiki/Lightning-prediction_system

[BravoV]

Ok, thanks though for the input, lets hear what others say about theirs, or their setup.

[CopperCone]

I think about that alot. A long time ago I had lighting hit near my house (back when I had a different hobby), and it fucked up all my routers, LAN cards, etc.

Normally I just turn off the power strips to my shit in bad weather, but,  Not sure if ground should be connected or not because sometimes I think the energy can come from a raised ground.. power strip does not disconnect ground, I think harmful energy can come through the filter capacitors with a highly raised lighting ground.

I have some where in my things to do list to make some kinda thing to disconnect my test equipment, and possibly the whole house, but I need to study lighting more.

Also obviously a hassle to disconnect stuff, and its kinda hit or miss.

I think if lighting strikes so close by, your gonna get fucked up equipment because of induction.

[kj7e]

I have been a Ham Radio Operator since I was 9 and have had many aerials and several large towers.  Plus I have built mountain top microwave sites and was RF Engineering supervisor TV Broadcast station.  The best way to deal with lightning is not to try and avoid it, but to give it somewhere to go.  I have seen it miss multiple 300' towers and strike buildings and power lines, it will strike where it wants to.  A solid ground path from the antenna to earth and a dispensation device in the feed line is great start.

In the photo above, a good solution would be some #4 solid copper from the base plate of the GPS Antenna (there is a ground lug there) straight down to an 8' ground rod and to use a PolyPhaser inline lightning arrestor before the feedline enters the building and also tie it with #4 copper to the ground rod.

https://www.polyphaser.com/products/rf-surge-protection/gt-nfsf-al

[BravoV]

A solid ground path from the antenna to earth and a dispensation device in the feed line is great start.

Hi kj7e, thanks for drop by.

As that photo is yours, I'm assuming that you didn't put that separated ground path (bare cable?) near your GPS antenna there ? Or its there ? As I can't see it clearly.

[orion242]

LOL, so what are you saying just keep prayin that the GPSDO, clock distributor, spectrum analyzer, freq. counter, scope and etc will be protected by The Almighty Thor god of lightning ? 

Skip Thor and go with home owners insurance.  It all fries, buy new...

[kj7e]

LOL, so what are you saying just keep prayin that the GPSDO, clock distributor, spectrum analyzer, freq. counter, scope and etc will be protected by The Almighty Thor god of lightning ? 

Skip Thor and go with home owners insurance.  It all fries, buy new...

That photo was taken just after it was mounted.  I had originally wanted to mount it on the eve of the roof but I had some ladder issues, so settled for this spot.  I always tie my aerials and feed line entry points to ground.  It may not protect the gear from a direct strike, but it will mitigate stray energy and and could keep you from being injured.

[Berni]

Skip Thor and go with home owners insurance.  It all fries, buy new...

I have wondered how well that would work. Usually you have to take your device to a repair shop for an estimate and bring that estimate to the insurance company.

All fine with the living room TV, but how does this work with test gear. Getting my Agilent scope to the official Keysight service means sending it via post as there is none close by and how is the insurance company going to look at the 5 grand to replace the acquisition board on one of these things when they don't even know what an oscilloscope is.

Then there are things like my HP spectrum analyzer from the 80s. It weighs 50kg so shipping it is not a simple thing and even if i got it to Keysight for repair its highly unlucky they would even repair something this old as they likely don't even have a lot of the parts for it anymore and nobody makes those parts anymore. So if it can't be fixed how is it written off.  Surely they wouldn't give you what one of these cost new as it cost as much as a pretty nice car back in the day, do you get what the ebay receipt says i bought it for?

[jbb]

I have wondered how well that would work. Usually you have to take your device to a repair shop for an estimate and bring that estimate to the insurance company.

All fine with the living room TV, but how does this work with test gear. Getting my Agilent scope to the official Keysight service means sending it via post as there is none close by and how is the insurance company going to look at the 5 grand to replace the acquisition board on one of these things when they don't even know what an oscilloscope is.

Then there are things like my HP spectrum analyzer from the 80s. It weighs 50kg so shipping it is not a simple thing and even if i got it to Keysight for repair its highly unlucky they would even repair something this old as they likely don't even have a lot of the parts for it anymore and nobody makes those parts anymore. So if it can't be fixed how is it written off.  Surely they wouldn't give you what one of these cost new as it cost as much as a pretty nice car back in the day, do you get what the ebay receipt says i bought it for?

I don't know how it works where you are, but it might be possible to list specific items (with costs) on your home & contents insurance policy (this may attract extra fees).  Then if something happens and your insurer gives you grief you can come back and say 'it's on the policy, you already accepted this value.'

[edpalmer42]

I have an idea, but I've never tried it. 

If you're reasonably far from the equator, you want your GPS antenna to have good visibility towards the equator because you'll see more satellites.  So, put up a steel pole, ground it, and mount the antenna *well below* the top of the pole on the side toward the equator.  This will make the steel pole the target for any lightning in the area, rather than your GPS antenna.  Add a lightning arrestor to the coax antenna feed and you're done.  The pole will block signal reception in that direction, but there's very little there anyway.

[Ian.M]

It depends what you need from the GPS.  If all you need is 1pps + NMEA data, you can have a receiver local to the antenna and run the receiver output over fibre optic cable.   Worst case you loose a relatively cheap GPS receiver, rather than all your lab test gear, (assuming the lab is a well-bonded equipotential zone and all other antennae and telecoms cabling are fed through GDT surge suppressors fitted to a well grounded bulkhead and disconnected with an adequate air gap on the lab side when not in use).

How many nearby lightning strikes have you had in the last year?

[jpb]

I've been wondering about this. I have an N-type surge protector (up to 6GHz) to connect to earth but driving an earth rod into the ground just where my utilities (Gas and Electricity) come into the house risks unfortunate accidents.
For timing having a good, direct view of several satellites is probably enough - satellites nearer the horizon are less important so I think I'll probably mount my antenna quite low  (about 6 to 8 ft off the ground) so any lightening strike is much more likely to hit the tall TV aerial on my chimney or one of the tall surrounding trees.

I might just connect the surge supressor indoors to provide some protection for the equipment from nearby strikes. I know it is much better to have an external and proper earth but it is a case of weighing up risks and convenience - and the need to get accurate plans of underground pipes and cables for a house built 30 years ago. Also, it is pointless doing it for the tiny GPS antenna and not taking similar precautions with the TV antenna and the satellite dish neither of which are protected as far as I know. I guess a lightening strike on either of them would fry more than my TV set.

Direct lightening hits are pretty rare where I am - I've not heard of one locally and the TV aerial has been there probably for decades and hasn't been hit yet.

[orion242]

I have wondered how well that would work. Usually you have to take your device to a repair shop for an estimate and bring that estimate to the insurance company.

Haven't had to make a claim yet, but I just talked with my insurance company and told them I have $xxx in electronics and I want replacement coverage.  Wasn't an issue and didn't add much to the policy.  Don't think I'll be dicking around with repairing any of it.  If it was lighting, its all likely BER anyway.

[edpalmer42]

I have wondered how well that would work. Usually you have to take your device to a repair shop for an estimate and bring that estimate to the insurance company.

Haven't had to make a claim yet, but I just talked with my insurance company and told them I have $xxx in electronics and I want replacement coverage.  Wasn't an issue and didn't add much to the policy.  Don't think I'll be dicking around with repairing any of it.  If it was lighting, its all likely BER anyway.

But Orion, BER is the starting point for EEVblog.   

[Berni]

Well its one thing when a PSU that gives like +/- 12V and 5V turns to charcoal and worst case you can replace the whole thing. Its another when the thing is full of proprietary ASICs and half of those boards are toast.

Still even if its BER the insurance company here will tend to want to see some proof of it. You can't just take a photo of it to prove its blown by lighting (Often no visible damage even on the boards inside) so they might want a certified service technician to declare it beyond repair.

[IanB]

I'm just an "enthusiast", planning to install an outdoor antenna for my GPS antenna for my upcoming GPSDO, and I don't have the outdoor antenna yet. Currently I don't have any clue how to deal with the lightning strike ?  :-//How do you deal with yours especially the outdoor antenna for your GPSDO ?

Home insurance. Definitely home insurance:

https://youtu.be/szOnAUnuMLk?t=46s

[TomS_]

Currently I don't have any clue how to deal with the lightning strike ? 

Communications towers, although typically being built of steel and quite well grounded, usually have what is called an "air terminal" on top. It a pole with maybe a few "bits and pieces" sticking out the top at various angles.

I suppose if lightning is going to strike, ideally it strikes right at the top of the tower at the air terminal, and makes its way down to ground from there, rather than striking antennas or any other part of the tower. But as already mentioned, it will strike where it wants to. You can only try and give it a "preferred" option.

You can see what I mean in this video, around the 6:45 mark. Its what hes holding on to. 

[BravoV]

In the photo above, a good solution would be some #4 solid copper from the base plate of the GPS Antenna (there is a ground lug there) straight down to an 8' ground rod and to use a PolyPhaser inline lightning arrestor before the feedline enters the building and also tie it with #4 copper to the ground rod.

https://www.polyphaser.com/products/rf-surge-protection/gt-nfsf-al

Thanks, looks like you added this after I posted mine below your post.

Noted, about the separated copper thick wire that is grounded for the lightning energy to pass through.

About the arrestor, there are so many types, just asking if the one that has the opening access for the GDT inspection or maybe for replacement is good compared to the one that is permanently sealed inside ?

Also about the antenna it self, I haven't purchase it yet, is this "decent" enough ? (attached below datasheet & photos)

Interested with this as the manufacturer claims that it has the integrated lighting protection, and don't worry, I will still provide the separated copper discharge line along the coax cable as you suggested.

[BravoV]

LOL, so what are you saying just keep prayin that the GPSDO, clock distributor, spectrum analyzer, freq. counter, scope and etc will be protected by The Almighty Thor god of lightning ? 

Skip Thor and go with home owners insurance.  It all fries, buy new...

Yes, I'm aware of insurance, but for now please put this topic aside temporarily, and discuss more on the technical topic.

[Distelzombie]

Couldn't you, theoretically, raise a big negative potential on the antenna or some metal around it? Lightning is  90-95% negative and should avoid it.
A'ma rite?

[BravoV]

It depends what you need from the GPS.  If all you need is 1pps + NMEA data, you can have a receiver local to the antenna and run the receiver output over fibre optic cable.   Worst case you loose a relatively cheap GPS receiver, rather than all your lab test gear, (assuming the lab is a well-bonded equipotential zone and all other antennae and telecoms cabling are fed through GDT surge suppressors fitted to a well grounded bulkhead and disconnected with an adequate air gap on the lab side when not in use).

This is interesting, as I only need to focus on the reciever's side protection like the lightning protection for the mains line that powered it.

This is becoming more expensive than I thought, as RS-232 to FO converters (pair) needed, and the separated power protection for the reciever + antenna side + fiber optic cables.

How many nearby lightning strikes have you had in the last year?

None I remembered since I live in my house for almost 20 years.

[Distelzombie]

Just found this: https://www.orau.org/ptp/collection/consumer%20products/lightningrod.htm
Maybe you can find some of these radioactive lightning-rods. xD