Ok stupid question I'm sure, but would putting a lightning arrestor in line with the antenna on a mobile install and grounding it to the car body provide any extra protection?
Lightning Arrestor On A Vehicle
- Thread starter LouisvilleScanMan
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No, because the shield of the coax is already grounded at two points (if the antenna is permanently mounted). One part of the shield is grounded at the antenna and the other side is grounded at the radio chassis through the ground wire.
On a house/base install, the antenna is not automatically grounded like it is in a car, so you have to create a ground for the antenna, usually using a ground rod. The radios should also be grounded as well.
On a house/base install, the antenna is not automatically grounded like it is in a car, so you have to create a ground for the antenna, usually using a ground rod. The radios should also be grounded as well.
Ok thanks
K9WG
Member
I beg to differ. I have driven along the edge of thunderstorms and had sparks jump from the center conducter of the coax (PL259) to the shield just from the charge in the air. It is very possible to have a static discharge without even being struck by lightning.
K9WG
Member
The idea is to "ground" the discharge from the antenna (center conductor) to the chassis ground. Ground potential is relative, whether earth or chassis. It is the voltage spike presented to the signal input relative to the radio chassis that does the damage.
rfradioconsult
Member
Precip static while driving through a shower especially at higher elevations can occur; however most gas discharge arrestirs "fire" at about 90 volts, that may or may not be high enough to cause damage to your radio. You could test your radio by tying 7 twelve volt car batteries in series and apply the voltage to your antenna input and chassis ground, if you choose to perform this test please post your results.
Richard's (WG) experience is so rare I never heard of such a thing in all of my 48 or so years involvement with radio and antennas. Although I wouldn't discount it entirely I say it's so rare as to be insignificant odds it would happen twice in a lifetime. It's fairly common with antennas having a very large mass such as long wires and broadcast towers in particular but with such a small antenna found on a mobile I wouldn't even give it a thought and never have.
Oh and BTW, something tells me some out there aren't used to Doc's occasionally sarcastic comments. (;->)
Oh and BTW, something tells me some out there aren't used to Doc's occasionally sarcastic comments. (;->)
bush_man
Member
lightning arrestor
Ok, I have been doing this a long time, scanning that is, and experienced something that scared the "s*$%" !!! out of me. Now I realize having a magnet top VHF antenna for my scanner isn't the smartest way of doing it, but that's what I have. I clip on the antenna and drive a mile or so to get a better look at the distant thunderstorm, like 20 miles minimum. I'm holding my scanner and all of a sudden ZAPPP, I get shocked from the screw on the back of the plastic scanner chassis. I tried to undo the BNC connector, big mistake, I took repeated shocks to the hands. I had to drop the scanner because I was getting hit repeatedly. I didn't dare try and get the antenna off the roof because obviously I was in a bad situation. Finally with doubled up leather glove, I was able to disconnect the BNC connector and put the BNC somewhere safe. The scanner survived, but this was a first and scared the crap outta me. I was wondering if this would have happened with a fender mount antenna vs. the magnet topper? I am saying no, because the chassis would have taken the hit, not the radio or me. Thoughts???
Ok, I have been doing this a long time, scanning that is, and experienced something that scared the "s*$%" !!! out of me. Now I realize having a magnet top VHF antenna for my scanner isn't the smartest way of doing it, but that's what I have. I clip on the antenna and drive a mile or so to get a better look at the distant thunderstorm, like 20 miles minimum. I'm holding my scanner and all of a sudden ZAPPP, I get shocked from the screw on the back of the plastic scanner chassis. I tried to undo the BNC connector, big mistake, I took repeated shocks to the hands. I had to drop the scanner because I was getting hit repeatedly. I didn't dare try and get the antenna off the roof because obviously I was in a bad situation. Finally with doubled up leather glove, I was able to disconnect the BNC connector and put the BNC somewhere safe. The scanner survived, but this was a first and scared the crap outta me. I was wondering if this would have happened with a fender mount antenna vs. the magnet topper? I am saying no, because the chassis would have taken the hit, not the radio or me. Thoughts???
BushDoctor
Member
I also have seen static charges jump from and pl 259 to its shell when working on mobiles outside from my many yearsof servicing Motorola radio equipment for public safety state, local and fed govts. I will relate an experience my brother had over 10 years ago operating a tractor trailer in oklahoma during a lightening storm his trailer was hot and left a rather large hole in the top of it but his i dont believe his CB survived cause he gave it to me for parts shortly after that happened but i never looked inside but still have it on a shelf in my radiop shack so guess i will do it next chance i get wb4igu
kb2vxa and all,
There is some sarcasm in my post above, but not that much, and my question was an honest one. Where, or how would you 'ground', or equalize the potential between a vehicle and whatever other potential that seems to be affecting it?
One method other than a "lightning arrester" is basically the same as 'fixed' stations may use, make the antenna have a direct connection to the vehicle's metal body/frame, through an inductor. A 'DC' grounded antenna. But then, that vehicle not being directly connected to the 'dirt' ground under it just has it's potential changed. It's still there, hasn't been dissipated. May not affect the scanner/radio, but what happens when you step out of that vehicle? Ever get a static discharge 'jolt' doing that? Many people have.
Fueling a metal bodied aircraft comes to mind! Ever seen that fuel person attach a grounding cable to the aircraft before opening the fuel cap, especially on larger aircraft? Helicopters are an even larger risk with static discharges.
Big difference between 'typical' static discharges and lightning. You can take precautions about static discharge, but there's really not much you can do about lightning or 'larger' voltage differences and mobiles. Think about it like if YOU were the discharge strap. nasty thought, huh??
- 'Doc
(Don't know about you, but the scanner/radio would be the least of my worries in that sort of situation. I'm more worried about ME!)
There is some sarcasm in my post above, but not that much, and my question was an honest one. Where, or how would you 'ground', or equalize the potential between a vehicle and whatever other potential that seems to be affecting it?
One method other than a "lightning arrester" is basically the same as 'fixed' stations may use, make the antenna have a direct connection to the vehicle's metal body/frame, through an inductor. A 'DC' grounded antenna. But then, that vehicle not being directly connected to the 'dirt' ground under it just has it's potential changed. It's still there, hasn't been dissipated. May not affect the scanner/radio, but what happens when you step out of that vehicle? Ever get a static discharge 'jolt' doing that? Many people have.
Fueling a metal bodied aircraft comes to mind! Ever seen that fuel person attach a grounding cable to the aircraft before opening the fuel cap, especially on larger aircraft? Helicopters are an even larger risk with static discharges.
Big difference between 'typical' static discharges and lightning. You can take precautions about static discharge, but there's really not much you can do about lightning or 'larger' voltage differences and mobiles. Think about it like if YOU were the discharge strap. nasty thought, huh??
- 'Doc
(Don't know about you, but the scanner/radio would be the least of my worries in that sort of situation. I'm more worried about ME!)
"Now I realize having a magnet top VHF antenna for my scanner isn't the smartest way of doing it, but that's what I have."
'Scuse me while I crack up. <pause> OK, now that's over with here's your answer besides "you're right about that". A magnet mount isn't in any way connected to the car body and nothing is grounded so in the electric field surrounding a thunderstorm opposite charges of thousands of volts can easily develop.
"Thoughts???"
Yeah, storm chasers who don't think out the consequences of their actions are candidates for the Darwin Award. The rest I'll keep to myself.............. (;->)
'Scuse me while I crack up. <pause> OK, now that's over with here's your answer besides "you're right about that". A magnet mount isn't in any way connected to the car body and nothing is grounded so in the electric field surrounding a thunderstorm opposite charges of thousands of volts can easily develop.
"Thoughts???"
Yeah, storm chasers who don't think out the consequences of their actions are candidates for the Darwin Award. The rest I'll keep to myself.............. (;->)
Doc, you hit the send button while I was typing or this would be one post. (;->) Anyway, I like your dry humor but that's beside the point.
"Where, or how would you 'ground', or equalize the potential between a vehicle and whatever other potential that seems to be affecting it?"
In a word, bonding. Within a vehicle methods are pretty obvious, flexible metal straps in the engine compartment and the dashboard along with any number of places where metallic contact is discontinuous. It's been such a long time since I've seen those static grounding straps you mounted under the car sold in auto parts stores I'd nearly forgotten but that was a way of bonding the car body to earth. I don't know what happened to those wire whiskers that stuck up under cars in toll lanes to protect the cashier and drivers from nasty static shocks either.
"Ever seen that fuel person attach a grounding cable to the aircraft before opening the fuel cap, especially on larger aircraft?"
Certainly, during my 7 years on the ramp at Newark International (EWR) I've assisted the fuelers connecting to trucks, hydrants and earthing the lot to terminals imbedded in the ramp area.
"Helicopters are an even larger risk with static discharges."
Yup, rotor flares look cool in night vision and I've heard Coast Guard helicopters radioing instructions on antistatic procedure many times.
"Big difference between 'typical' static discharges and lightning."
Really? (;->)
"You can take precautions about static discharge, but there's really not much you can do about lightning or 'larger' voltage differences and mobiles."
Sure you can, STAY IN THE DANG CAR AND DON'T TOUCH ANYTHING! A vehicle body is a Faraday cage that can lead any discharge no matter how massive around the occupants often leaving nothing more than a pinhole where the bolt struck.
"Think about it like if YOU were the discharge strap."
I don't have to think, the memory of adjusting the arc gap on a tower while a storm was approaching is indelibly burned into my brain and probably took out a few neurons with it.
"Where, or how would you 'ground', or equalize the potential between a vehicle and whatever other potential that seems to be affecting it?"
In a word, bonding. Within a vehicle methods are pretty obvious, flexible metal straps in the engine compartment and the dashboard along with any number of places where metallic contact is discontinuous. It's been such a long time since I've seen those static grounding straps you mounted under the car sold in auto parts stores I'd nearly forgotten but that was a way of bonding the car body to earth. I don't know what happened to those wire whiskers that stuck up under cars in toll lanes to protect the cashier and drivers from nasty static shocks either.
"Ever seen that fuel person attach a grounding cable to the aircraft before opening the fuel cap, especially on larger aircraft?"
Certainly, during my 7 years on the ramp at Newark International (EWR) I've assisted the fuelers connecting to trucks, hydrants and earthing the lot to terminals imbedded in the ramp area.
"Helicopters are an even larger risk with static discharges."
Yup, rotor flares look cool in night vision and I've heard Coast Guard helicopters radioing instructions on antistatic procedure many times.
"Big difference between 'typical' static discharges and lightning."
Really? (;->)
"You can take precautions about static discharge, but there's really not much you can do about lightning or 'larger' voltage differences and mobiles."
Sure you can, STAY IN THE DANG CAR AND DON'T TOUCH ANYTHING! A vehicle body is a Faraday cage that can lead any discharge no matter how massive around the occupants often leaving nothing more than a pinhole where the bolt struck.
"Think about it like if YOU were the discharge strap."
I don't have to think, the memory of adjusting the arc gap on a tower while a storm was approaching is indelibly burned into my brain and probably took out a few neurons with it.
Interesting topic. Static build up happens all the time as you drive. From wind, rubber on the road etc. Thats why there are little wires sticking up out of the road prior to a toll booth, to keep the bill grabbers from getting zapped from every car. Bad weather and even a nearby lightning strike will raise the potential of your vehicle more.
Is this bad? No, happens all the time. Do you need to ground or bleed off this potential? No, unless it's real high and you would like to step out!
I agree with K9WG. A voltage rise on the antenna input of a radio would only cause damage IF there is no like rise on the radios chassis (ground reference). Lightning could hit the car direct and charge it to a gazillion volts, but if all parts of the radio are at a gazillion volts there is no potential difference internally and thus no damage (theoretically, don't have the stones to test personally). Really no need to ground the car, you and the radio will survive (I hope).
The question is whether a high voltage will appear on the antenna input and not the rest of the radio. Sounds like posters do have experiences with this although I never have. If it does, then a arrestor should help by clamping the antenna to the chassis ground and allow the radio to rise all at once and prevent a potential difference inside. Someone mentioned gas discharge tubes fire at 90 volts. This is actually very good. Some arrestors will pass as much as 600 volts before they clamp, but they do so in the order of nano seconds and only let a small amount of energy (in joules) pass through. This may only put a small pit in a transistors junction whereas seven car batteries in series will vaporize the junction. A DC grounded antenna also works, but on fast EMP, the impedance of the coil that provides this also comes into play.
So what do I think? If you're skiddish about your radio then a lightning arrestor and/or DC grounded antenna surely couldn't hurt, and forget about dragging an eight foot ground rod behind the car.
Is this bad? No, happens all the time. Do you need to ground or bleed off this potential? No, unless it's real high and you would like to step out!
I agree with K9WG. A voltage rise on the antenna input of a radio would only cause damage IF there is no like rise on the radios chassis (ground reference). Lightning could hit the car direct and charge it to a gazillion volts, but if all parts of the radio are at a gazillion volts there is no potential difference internally and thus no damage (theoretically, don't have the stones to test personally). Really no need to ground the car, you and the radio will survive (I hope).
The question is whether a high voltage will appear on the antenna input and not the rest of the radio. Sounds like posters do have experiences with this although I never have. If it does, then a arrestor should help by clamping the antenna to the chassis ground and allow the radio to rise all at once and prevent a potential difference inside. Someone mentioned gas discharge tubes fire at 90 volts. This is actually very good. Some arrestors will pass as much as 600 volts before they clamp, but they do so in the order of nano seconds and only let a small amount of energy (in joules) pass through. This may only put a small pit in a transistors junction whereas seven car batteries in series will vaporize the junction. A DC grounded antenna also works, but on fast EMP, the impedance of the coil that provides this also comes into play.
So what do I think? If you're skiddish about your radio then a lightning arrestor and/or DC grounded antenna surely couldn't hurt, and forget about dragging an eight foot ground rod behind the car.
bush_man
Member
follow up
Now that the lynch mob has toned down a bit, I didn't ask my question to get insulted, but I can see how it was concededly amusing. If there is no way to ground a vehicle antenna, then there was no reason to slam the fact that I was using a magnet mount antenna, as all I was touching was the radio inside the vehicle. Regardless, I wasn't taken serious, other than a few of you pretty much said, its user beware, while driving. Imagine, thunderstorms in the summer in the midwest...hmmmm....and storm chasers get paid for their stuff, I just wanted to see if it was time to duck and cover....lol
Now that the lynch mob has toned down a bit, I didn't ask my question to get insulted, but I can see how it was concededly amusing. If there is no way to ground a vehicle antenna, then there was no reason to slam the fact that I was using a magnet mount antenna, as all I was touching was the radio inside the vehicle. Regardless, I wasn't taken serious, other than a few of you pretty much said, its user beware, while driving. Imagine, thunderstorms in the summer in the midwest...hmmmm....and storm chasers get paid for their stuff, I just wanted to see if it was time to duck and cover....lol
reedeb
Member
I don't know if this will help, I found this Magnetic Mount Antennas are Electrical Performers You may find some answers here. And no lynching, I may get the whip out or the bat [lol]
And just for grins...
Those static discharge straps that used to be sold for cars/trucks don't work. They can cause as much if not more, static than they will ever 'cure'. If you just have to have some means of discharging static electricity from a moving vehicle why not do like the aircraft industry does? Ever see a sort of 'fuzzed-out' woven metal strap on the trailing edge of a wing or tail structure? Yep, static discharge straps. They're usually placed symmetrically, on both sides of the aircraft. Hate to drain the static from just one side... you know?
- 'Doc
('bush_man' - none of this is a 'dig' at you. And you gotta admit, some of it really is funny.)
Those static discharge straps that used to be sold for cars/trucks don't work. They can cause as much if not more, static than they will ever 'cure'. If you just have to have some means of discharging static electricity from a moving vehicle why not do like the aircraft industry does? Ever see a sort of 'fuzzed-out' woven metal strap on the trailing edge of a wing or tail structure? Yep, static discharge straps. They're usually placed symmetrically, on both sides of the aircraft. Hate to drain the static from just one side... you know?
- 'Doc
('bush_man' - none of this is a 'dig' at you. And you gotta admit, some of it really is funny.)
Howdy
Outside of the 'comedy-central' attempts from some prior post, the advice of 'bonding' is likely the best bet and what the Military Command Hummer's (HF/VHF/UHF/SATCOM) and the like have in place to try to minimize static damage in the desert conditions, along with having Mil-Spec gear naturally.
Thx
Bill
Outside of the 'comedy-central' attempts from some prior post, the advice of 'bonding' is likely the best bet and what the Military Command Hummer's (HF/VHF/UHF/SATCOM) and the like have in place to try to minimize static damage in the desert conditions, along with having Mil-Spec gear naturally.
Thx
Bill
reedeb
Member
NOW could we have the ENGLISH translation? .
AK4GA
Member
No, just no.
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