How to reduce/mitigate the risk of lightning at the GPS outdoor antenna ? - Page 1
Forum section: electronics / projects

author: BravoV
author_rank: Super Contributor
timestamp: April 19, 2018, 06:33:48 pm
content: 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 thisPostClick photo to enlarge.How do you deal with yours especially the outdoor antenna for your GPSDO ?

author: CopperCone
author_rank: Super Contributor
timestamp: April 19, 2018, 06:36:44 pm
content: 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.

author: BravoV
author_rank: Super Contributor
timestamp: April 19, 2018, 06:42:05 pm
content: Quote from: CopperCone on April 19, 2018, 06:36:44 pmLOL, 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 ?

author: CopperCone
author_rank: Super Contributor
timestamp: April 19, 2018, 06:43:45 pm
content: 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 andhttps://en.wikipedia.org/wiki/Lightning-prediction_system

author: BravoV
author_rank: Super Contributor
timestamp: April 19, 2018, 06:45:56 pm
content: Ok, thanks though for the input, lets hear what others say about theirs, or their setup.

author: CopperCone
author_rank: Super Contributor
timestamp: April 19, 2018, 06:56:48 pm
content: 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.

author: kj7e
author_rank: Frequent Contributor
timestamp: April 19, 2018, 07:03:08 pm
content: 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

author: BravoV
author_rank: Super Contributor
timestamp: April 19, 2018, 07:09:27 pm
content: Quote from: kj7e on April 19, 2018, 07:03:08 pmHi 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.

author: orion242
author_rank: Unknown
timestamp: April 19, 2018, 07:13:56 pm
content: Quote from: BravoV on April 19, 2018, 06:42:05 pmSkip Thor and go with home owners insurance. It all fries, buy new...

author: kj7e
author_rank: Frequent Contributor
timestamp: April 19, 2018, 07:24:11 pm
content: Quote from: orion242 on April 19, 2018, 07:13:56 pmThat 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.

author: Berni
author_rank: Super Contributor
timestamp: April 19, 2018, 07:32:05 pm
content: Quote from: orion242 on April 19, 2018, 07:13:56 pmI 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?

author: jbb
author_rank: Super Contributor
timestamp: April 19, 2018, 08:06:58 pm
content: Quote from: Berni on April 19, 2018, 07:32:05 pmI 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, youalready acceptedthis value.'

author: edpalmer42
author_rank: Super Contributor
timestamp: April 19, 2018, 08:23:15 pm
content: 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.

author: Ian.M
author_rank: Super Contributor
timestamp: April 19, 2018, 08:53:41 pm
content: 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?

author: jpb
author_rank: Super Contributor
timestamp: April 19, 2018, 09:04:07 pm
content: 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.

author: orion242
author_rank: Unknown
timestamp: April 19, 2018, 11:38:03 pm
content: Quote from: Berni on April 19, 2018, 07:32:05 pmHaven'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.

author: edpalmer42
author_rank: Super Contributor
timestamp: April 20, 2018, 05:09:16 am
content: Quote from: orion242 on April 19, 2018, 11:38:03 pmBut Orion, BER is thestartingpoint for EEVblog.

author: Berni
author_rank: Super Contributor
timestamp: April 20, 2018, 05:24:20 am
content: 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.

author: IanB
author_rank: Super Contributor
timestamp: April 20, 2018, 05:38:34 am
content: Quote from: BravoV on April 19, 2018, 06:33:48 pmHome insurance. Definitely home insurance:https://youtu.be/szOnAUnuMLk?t=46s

author: TomS_
author_rank: Frequent Contributor
timestamp: April 20, 2018, 09:00:25 am
content: Quote from: BravoV on April 19, 2018, 06:33:48 pmCommunications 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.

author: BravoV
author_rank: Super Contributor
timestamp: April 20, 2018, 09:59:00 am
content: Quote from: kj7e on April 19, 2018, 07:03:08 pmThanks, 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.

author: BravoV
author_rank: Super Contributor
timestamp: April 20, 2018, 10:02:59 am
content: Quote from: orion242 on April 19, 2018, 07:13:56 pmYes, I'm aware of insurance, but for now please put this topic aside temporarily, and discuss more on the technical topic.

author: Distelzombie
author_rank: Frequent Contributor
timestamp: April 20, 2018, 10:07:00 am
content: 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?

author: BravoV
author_rank: Super Contributor
timestamp: April 20, 2018, 10:08:20 am
content: Quote from: Ian.M on April 19, 2018, 08:53:41 pmThis 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.Quote from: Ian.M on April 19, 2018, 08:53:41 pmNone I remembered since I live in my house for almost 20 years.

author: Distelzombie
author_rank: Frequent Contributor
timestamp: April 20, 2018, 10:30:45 am
content: Just found this:https://www.orau.org/ptp/collection/consumer%20products/lightningrod.htmMaybe you can find some of these radioactive lightning-rods. xD

author: Ian.M
author_rank: Super Contributor
timestamp: April 20, 2018, 10:53:50 am
content: Its only the 1pps signal that's critical. If you use a cheap transmitter and DC coupled receiver pair, + polymer fibre optic cable, you can probably roll your own isolated link for about $30. You don't have to run fibre all the way - once youv'e gone far enough that the risk of a side flash from the lightning protection conductor is minimal, you can transition back to copper. The NMEA0183 can be handled using an off-the-shelf RF datalink as its latency is far less critical.However powering it, short of a dedicated solar panel and battery is more problematic . . . .

author: GreyWoolfe
author_rank: Unknown
timestamp: April 20, 2018, 11:19:16 am
content: Here in Florida, the lightning capital of the US, lightning is a constant worry. I don't use Polyphasers, ground rods or anything fancy. If I am not playing radio, the 80 meter full wave loop and commercial 2 meter vertical antennas are disconnected. Period. I had a lightning strike hit the street in front of the house a number of years ago. A 5/8 wave 2 meter antenna on the roof of the house, was partially gone, the loading coil inside was vaporized and 75 ft of coax was toasted. The dielectric at the connector in the house was black. No radio was harmed. All the damage happened to the cable box, cable modem, the router connected to it and a couple of computers connected to the router. I personally would be nervous having any antenna permanently connected. Bravo, glad lightning isn't as big a concern for you. My 2 cents, whatever you do, add the polyphaser. In another galaxy far, far away and long ago, I used something like this for my CB radio connected to the cold water copper pipe.

author: BravoV
author_rank: Super Contributor
timestamp: April 20, 2018, 12:21:12 pm
content: Quote from: Ian.M on April 20, 2018, 10:53:50 amSorry, as I'm a noob on GPSDO thingies as its my 1st, just realized that I need the 10 MHz signal which is the main reason why all this troubles, I guess isolating this it self can't be cheap ? CMMIIW

author: Ian.M
author_rank: Super Contributor
timestamp: April 20, 2018, 01:39:22 pm
content: No, fibre isolating 10MHz wont be easy to roll your own for. However many GPSDOs use the 10KHz output available from some receivers and fibre isolating 10KHz is probably even easier than 1pps as with a constant AC signal present, the fibre receiver can be AC coupled and have AGC.

author: jmelson
author_rank: Super Contributor
timestamp: April 20, 2018, 10:57:44 pm
content: If it is like the picture, the building mostly protects it. But, if the building takes a direct lightning hit, then anything can happen. You can have MAJOR sparks flashing across from the electrical wiring to the plumbing, set the wood on fire, etc. If the building or the power poles outside get a direct hit, very likely everything in the building, often including the wiring in the walls, will be fried.So, what you CAN do is protect against NEARBY strikes. One thing that causes a lot of damage is induced currents/voltages produced in wiring loops. So, for instance, you have the electrical wires to an office with a bunch of computer gear travel through the West wall. But, you pull network cables through the ceiling. That forms a loop, and the voltages induced there can be substantial. Reducing the loop area will reduce the induced voltage. But, this may not be real practical to do in existing buildings.Jon

author: BravoV
author_rank: Super Contributor
timestamp: May 09, 2018, 06:53:30 am
content: I've read and searched lots of lightning protection literatures for antenna, still not clear how to proceed with my installation, any experienced fellows help will be appreciated.Assuming we follow this common good practice, here is the standard lightning protection scheme and illustration from HP 58503A/B GPSDO manual, its clear here that the lightning rod and the cable to earth is separated from the GPS antenna and has it's own lightning protection and then joined (item no 11) together at the ground wire (the red square at the ground cable).My antenna has the integrated lightning protector, as seen below photo, the big earth wire connection with the antenna N type connector at the background. Should I provide "another" separated ground wire from this connector down to earth, or I can just connect/join this directly to the lightning rod say at the roof up there ? Cause using separated cables, that will be quite an expensive installation.

author: IanB
author_rank: Super Contributor
timestamp: May 11, 2018, 03:21:17 am
content: Quote from: BravoV on May 09, 2018, 06:53:30 amI'd say you should follow the given instructions very carefully and precisely. If you change things around and deviate from what the drawing shows without knowing what you are doing you could invalidate the whole scheme and render it useless.(The whole idea of connecting something "directly to the lightning rod" sounds a bit scary. The goal of a lightning rod is to collect charge and direct it safely away from the thing being protected. Not to collect charge and conduct it right up to the back door of the thing being protected.)

author: BravoV
author_rank: Super Contributor
timestamp: May 11, 2018, 03:37:48 am
content: Quote from: IanB on May 11, 2018, 03:21:17 amActually I don't plan to change anything at all, the GPS antenna in the HP illustration does not have the lightning protection as mine does, look again.I've been searching for quite sometimes now on the GPS antenna that has protection on the "detail" installation, but still no luck, yes, that includes Huber+Suhner web site.Quote from: IanB on May 11, 2018, 03:21:17 amYeah, thats the instinctively thinking, todriveopen higher possibilities that the lightning will strike else where "away" from the antenna.I guess I will have to use separated ground line connected at the antenna.Thanks for your concern.PS : Attached datasheet of the antenna.

author: matthuszagh
author_rank: Frequent Contributor
timestamp: January 08, 2025, 03:13:14 pm
content: Quote from: BravoV on May 09, 2018, 06:53:30 amHi BravoV. Would you be willing to point me to that manual, or share that document with me? I've poked around the various HP 58503A/B manuals I was able to find online, but unfortunately I haven't been able to track down that diagram.Out of curiosity, do you have (or did you install) a lightning rod? This would definitely add to the expense and complicate the installation. Moreover, based on my reading of NEC 810, it's not required. But, I imagine it adds significant protection if properly done.