Surge Protection for Mobile Installation

[Abies]

Assuming proper installation in all respects, including grounding, is there any value in providing surge protection in the coax line? I'm thinking of a coax switch (one where the off position grounds the antenna line) and/or a standard coax surge protector. The vehicle will often be in the field where there is a possibility of a lightning strike nearby.

What about the DC line going to the radio? Should that have surge protection, or will proper grounding of the system take care of that concern?

 

[RFI-EMI-GUY]

My E350 van that had decades ago with CB (NMO-27) and GMRS (NMO 1/4 wave) actually got struck by lightning while parked outside the window at my office. There was paint damaged at roof near the center brake light and I think the charge went through the frame and trailer hitch to ground where I found a fulgarite in the sandy soil. But miraculously, nothing was damaged.

But yeah, it could get hit and damaged. Grounding everything properly is your first line of defense. As far as protectors on the DC, unless you have some very valuable gear and a fiberglass body, I would not be concerned. An HF antenna of any sort would warrant a protector. I would say it is a risk assessment you need to make. I have in my lifetime two lightning strikes at home. Both causing damage. The second one much more serious. I should have called in my insurance due to later finding my pool light wiring getting knocked out amongst other things.

 

[hill]

My E350 van that had decades ago with CB (NMO-27) and GMRS (NMO 1/4 wave) actually got struck by lightning while parked outside the window at my office.

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After my brother passed away and the lady that got his Hyundai Santa Fe. It got struck by lightning less Then a year later and was totaled with the amount of electronics in modem vehicles.

I wouldn't really worry about this with it being very rare.

 

[Abies]

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After my brother passed away and the lady that got his Hyundai Santa Fe. It got struck by lightning less Then a year later and was totaled with the amount of electronics in modem vehicles.

I wouldn't really worry about this with it being very rare.

It's not so much a matter of a direct strike, which as you state is rare. Rather, it's a nearby strike which could cause induced current, enough to damage electronics. This is also a factor for base stations; the odds of a direct strike are small compared to those of a nearby strike. I've had two strikes in my lifetime (that I can remember) that were within a couple hundred feet of my residence at the time, and that's living in lowland California where lightning is relatively rare. The mountains are a whole other story in that regard.

My new vehicle (replacing my old 4x4) will often used be in mountainous regions. The best sites there for radio use are ridges and summits (aside from my other reasons for going to such spots such as photography). Of course one should exercise due caution in inclement weather and try to move out of harm's way, but in practice one can be caught by surprise, especially while sleeping.

 

[slowmover]

Big truck manufacturers & fleets make no provision for such.

Not all antennas are external. Image is of the composite material above the windshield with a HIRSCHMANN Thin Film Antenna.



On some current fleet trucks are twin mirror-mount whips where one is CB, the other is AM/FM.

On many older trucks are driver/owner aftermarket set/ups. Wide variations.

Strikes can occur. I’ve heard of a few. But the industry as a whole doesn’t regard it as likely.

That’s the largest user group of mobile HF.
The insurers would have a say in things. No one but the driver gives a good G-D if he’s without a CB.

.

 

[slowmover]

Agreed that mountain ridges are another kettle of fish. I’d finish that stew early then move downslope.

Good luck

 

[kayn1n32008]

Assuming proper installation in all respects, including grounding, is there any value in providing surge protection in the coax line? I'm thinking of a coax switch (one where the off position grounds the antenna line) and/or a standard coax surge protector. The vehicle will often be in the field where there is a possibility of a lightning strike nearby.

What about the DC line going to the radio? Should that have surge protection, or will proper grounding of the system take care of that concern?

You are WAY over thinking a problem that really isn't an issue.

Where exactly are you disappating an Induced current to? Your 'ground' is the negative side of a DC power system that is 'floating' independently of the earth. You don't have an 'earth' ground in a mobile instalation, like you would with an AC powered fixed site like a repeater or a home station.

 

[hazrat8990]

Assuming proper installation in all respects, including grounding, is there any value in providing surge protection in the coax line? I'm thinking of a coax switch (one where the off position grounds the antenna line) and/or a standard coax surge protector. The vehicle will often be in the field where there is a possibility of a lightning strike nearby.

What about the DC line going to the radio? Should that have surge protection, or will proper grounding of the system take care of that concern?

Most commercially made antennas with any sort of loading coil are DC grounded, and will show a dead short if you test them with a multimeter. There's nothing wrong with adding additional grounds, or bonding straps to body panels etc. In fact, it will most likely help with reducing, or eliminating RFI and also help to dissipate static. However, everything can, and probably will be affected by a direct strike.

 

[mmckenna]

I agree, I think you are over thinking this.

I've had some nearby strikes, but never had any issues with the vehicles or the radios. This was everything from CB to VHF, UHF and 800MHz.
What makes a difference is making sure everything is at the same potential.

Permanenet mount antennas where there is a direct connection to the body at the antenna base. As mentioned above, DC grounded antennas might have a slight benefit. There's a small gap at the antenna mount, and the lightning will jump that if it decides it wants to go to the body.

The negative power lead from your radio should go straight to a body ground, not all the way back to the battery.
The positive power lead from your radio should go straight to the battery positive with a suitable fuse/breaker.
I usually run a separate ground from the radio chassis direct to the body ground also.

None of that is specific to lightning, that's just good install practices. Good grounding helps, but like it was said, your vehicle isn't really 'grounded'. Any lightning strike that is going to damage your radio is probably going to make a mess of your car electronics unless you get luckly. Lightning does wierd things.

In all the installation manuals I've read from Motorola, Kenwood and Harris, I've never seen anything that was designed around lightning strikes. But they all shared similar install practices.

 

[Abies]

Thanks, everyone for your helpful replies!

 

[slowmover]

A big chunk of metal on a tree-less mountain ridge is even more of a target than a human traversing it.

It ain’t “overthinking”. It was a sensible question.

Generally, not a problem given proper method.
Risk, is location over all else.



.

 

[prcguy]

It's not so much a matter of a direct strike, which as you state is rare. Rather, it's a nearby strike which could cause induced current, enough to damage electronics. This is also a factor for base stations; the odds of a direct strike are small compared to those of a nearby strike. I've had two strikes in my lifetime (that I can remember) that were within a couple hundred feet of my residence at the time, and that's living in lowland California where lightning is relatively rare. The mountains are a whole other story in that regard.

My new vehicle (replacing my old 4x4) will often used be in mountainous regions. The best sites there for radio use are ridges and summits (aside from my other reasons for going to such spots such as photography). Of course one should exercise due caution in inclement weather and try to move out of harm's way, but in practice one can be caught by surprise, especially while sleeping.

What make/model is your new vehicle?

 

[Abies]

A big chunk of metal on a tree-less mountain ridge is even more of a target than a human traversing it.

It ain’t “overthinking”. It was a sensible question.

Generally, not a problem given proper method.
Risk, is location over all else.

View attachment 194656

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The diagram is helpful and contains the standard lightning-safety advice. Still, it doesn't fully express the topographic diversity of situations out there that I've experienced over the decades. For instance, one may be in a very large and generally high area where the valleys may be shallow and not far below the ridges. Or, topography may consist of gently rolling uplands cut by occasional inaccessible river canyons.

I'm confident that maintaining situational awareness and using common sense will be effective in minimizing lightning risk the vast majority of the time, but not always. The disastrous 2020 Creek Fire in California appears to have started from the lightning strike near the bottom of a 2000'-deep canyon, for example.

In some cases weather can sneak up on you. I had that happen to me decades ago. At sunset there were just some puffy small clouds, but later I was extremely surprised to find a lightning storm had started. (The usual thunderstorm pattern in the mountains of California is daytime development of storms, which peak in the afternoon then die down late in the day, though I've seen exceptions to that.)

It all comes down to informed risk management. I know that some of my past choices in retrospect were too risky, but it's also not realistic to always retreat to deep valleys in case something develops overnight. A lot of remote areas don't have internet access, though I may be able to tune in to NOAA weather.

What make/model is your new vehicle?

Ford Bronco. Right now a shop is installing an aftermarket aluminum top. That will provide a good ground plane, unlike the OEM soft top or non-metallic hard top. It should also function like an integrated metal roof in case of a direct strike. I will be sleeping in the vehicle sometimes.

 

[enine]

You are WAY over thinking a problem that really isn't an issue.

Where exactly are you disappating an Induced current to? Your 'ground' is the negative side of a DC power system that is 'floating' independently of the earth. You don't have an 'earth' ground in a mobile instalation, like you would with an AC powered fixed site like a repeater or a home station.

Vehicle tires have been made slightly conductive for decades to dissipate static electricity. SO while its not a great ground like a rod in the dirt is still is a ground.