Coax Surge Arrestors

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DJX

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I'm looking at picking up a good surge arrestor and was wondering if someone can lend an opinion between these two arrestors:

Times Microwave LP-GTR-NFF-23
(Heard you can't go wrong with Times)

Diamond Antenna SP3000W
(I have a Diamond Antenna)

Also, can someone verify what exactly "freq range: DC - 3GHz" actualy covers?
Is that 0Hz - 3GHz?

Thanks.
 

W2PMX

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You're right - you can't go wrong with Times. And yes, the arrestor will pass 0Hz (DC) and the attenuation at 3GHz is barely measurable. Just remember, though, that these are surge arrestors, not lightning protection. The only thing that's guaranteed to protect the radio from a direct hit is to not have it connected to the coax. (Thinking that you can "protect" a radio from 100 million volts or more is pure fantasy - as in Doc Smith's stories.)
 

DJX

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Thanks for the info.
I'm leaning more towards the Times one, even though it's twice as expensive.

You said these are not lighting protection but on the PDF here: http://www.timesmicrowave.com/products/protect/downloads/GTRN.pdf
It states:
The Times-Protect™ LP-GTR-N series is an exceptional
broadband DC pass design for lightning protection
applications...
I don't mean to nitpick, I'm just reading about the product.

Thanks again.
 

LtDoc

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Those surge protectors have a very definite purpose that may not be applicable to some applications. If it 'fits' you particular application then it's probably not a bad idea.
It's also very safe in saying that they will not be an absolute protection with lightning strikes, or near ones. I honestly don't know of any 'sure-fire' protection with that. Even completely disconnecting a radio is not guarantee. (Just how 'close' is 'close? You know?)
- 'Doc

(And no, I'm not 'Doc Smith'! :))
 

W2PMX

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A nearby (a few hundred feet) strike can induce thousands of volts into a length of coax (inductive coupling). Good gas-gap surge protectors can handle that. That's a "lightning protection
application". A direct hit? I saw a broadcast tower - all 330 feet of it - disappear after a direct strike. All that was left was the concrete base it has stood on. Yes, it had lightning "protection" - 2 large steel balls, about the size of volleyballs, one coming from the tower, the other one grounded. When we arrived for work the morning after the storm the 4-tower station was a 3-tower station.

Trying to "protect" against a direct strike is a cheap form of suicide, one that saves the family the cost of a funeral. There's nothing to bury. (People who have been "struck by lightning" and survived were probably hit by leaders, secondary strikes or induced sparks.) Please don't ever assume that anything you do is going to protect you from lightning - it won't.
 

prcguy

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I would say more than half of a lightning protection system is in the grounding and not the actual coax arrestor. Without a properly designed ground system the arrestor can't do it's job and thinking your protected when your not is worse than not being protected and knowing it.

With that said its very difficult to add the required grounding system to a residence to guarantee protection from a direct lightning hit and at best it may suffice for nearby strikes in reducing high voltages induced on long wire HF antennas.

Read up on NEC Article 810 for minimum grounding requirements for antennas then maybe the Polyphaser lightning book for excellent explanations and diagrams of grounding systems for lightning protection.
prcguy
 

prcguy

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Interesting...
We have towers on 5,000+ ft mountaintops that receive direct hits every year and at worst some antenna tips get burnt off. I've never heard of anything but wire and smaller diameter antennas being completely vaporized by lightning.

When properly designed from the ground up (pun intended) a radio site can withstand multiple direct hits with no damage to the electronics but it's not something you can achieve at home unless it was built like a mountaintop radio site.
prcguy



A nearby (a few hundred feet) strike can induce thousands of volts into a length of coax (inductive coupling). Good gas-gap surge protectors can handle that. That's a "lightning protection
application". A direct hit? I saw a broadcast tower - all 330 feet of it - disappear after a direct strike. All that was left was the concrete base it has stood on. Yes, it had lightning "protection" - 2 large steel balls, about the size of volleyballs, one coming from the tower, the other one grounded. When we arrived for work the morning after the storm the 4-tower station was a 3-tower station.

Trying to "protect" against a direct strike is a cheap form of suicide, one that saves the family the cost of a funeral. There's nothing to bury. (People who have been "struck by lightning" and survived were probably hit by leaders, secondary strikes or induced sparks.) Please don't ever assume that anything you do is going to protect you from lightning - it won't.
 

W2PMX

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Interesting...
We have towers on 5,000+ ft mountaintops that receive direct hits every year and at worst some antenna tips get burnt off. I've never heard of anything but wire and smaller diameter antennas being completely vaporized by lightning.

When properly designed from the ground up (pun intended) a radio site can withstand multiple direct hits with no damage to the electronics but it's not something you can achieve at home unless it was built like a mountaintop radio site.
prcguy
That depends on the hit. Leader? Single strike? High or lower voltage? High or lower current?

Lightning isn't like 120 volts, 20 amps, it's a very wide range (and that probably qualifies to at least be in the running for understatement of the century) of voltages and currents. Typical currents run around 5kA to 20kA, but the famous strike just before the Apollo 15 launch in 1971 was measured at 100kA, and currents of over 200kA have been measured. And Williams (MIT Lincoln Laboratory) has reported voltages in the several hundred MV range. So we're talking about a possibility of over 200gW being dissipated by a few tons of steel in less than 100 microseconds. Anyone want to guess what the temperature of that tower will be under those conditions? Hotter than the sun or cooler?

My money is always on the human losing in a human/lightning match.
 

prcguy

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Much of Los Angeles is powered by Hoover Dam near Las Vegas and sent via Direct Current to a major switching station in Sylmar CA where I got to tour the facility many years ago.

At the time the average power delivered to the station was either 1 million volts at 750,000 amps or 750,000 volts at 1 million amps. Either way its thesame amount of power and it's delivered over several 4 to 6in diameter hollow aluminum "cables" all the way across the desert. That's 750 Billion watts unless I'm counting wrong and probably not much more metal surface area than a 33ft tower would have.

I can see the top of a tower getting burnt off and the concrete base exploding but no way 330ft of a substantial tower just evaporated. Maybe the guy cables were zapped and it fell over but even the largest lightning strike on the planet does not make that much metal disappear.
prcguy




A
That depends on the hit. Leader? Single strike? High or lower voltage? High or lower current?

Lightning isn't like 120 volts, 20 amps, it's a very wide range (and that probably qualifies to at least be in the running for understatement of the century) of voltages and currents. Typical currents run around 5kA to 20kA, but the famous strike just before the Apollo 15 launch in 1971 was measured at 100kA, and currents of over 200kA have been measured. And Williams (MIT Lincoln Laboratory) has reported voltages in the several hundred MV range. So we're talking about a possibility of over 200gW being dissipated by a few tons of steel in less than 100 microseconds. Anyone want to guess what the temperature of that tower will be under those conditions? Hotter than the sun or cooler?

My money is always on the human losing in a human/lightning match.
 

Baskt_Case

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Yea, when I use to climb cell towers years ago, quite a few sites had strike counters installed inside the shack. Some of them indicated many hundreds of strikes. The site engineers claimed that if we were on the rig during a direct hit, we would merely suffer burnt hands and possibly flash blindness as the lightning rushed passed us on the way to ground, but we sure never wanted to find out. We couldnt get off those things fast enough once the forecasts came in. I've ridden plenty of exciting things in my life but I'll pass on that one.

Yes, in a direct hit scenario, damage will be done. We can mitigate these effects to some extent, but cannot avoid them entirely. Giving the lightning what it wants, the fastest/shortest path to ground, is still the best defense. At least in preventing a house fire. As for your antenna? Exspensive marshmallow roaster. I dont ever count on being completely protected, so I'll settle for knowing the lightning at least has the *option* of taking the ground path instead of torching my house.

Those arrestor/diffuser contraptions are nice, but if the path from arrestor to ground is long enough, it might jump the gap anyway. Or find some other convenient target. Lightning is a beast in panic. Compare it to a raging rodeo-bull, in your living room. Whats it gonna do?
 
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mpddigital

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The Times arrestors are great. The are more expensive but how much is your equipment worth? The Times and Suhner protectors have great reps and will take much more abuse than the Chinese knockoffs. We have found some of the really cheap chinese ones to be not much more than a piece of threaded pipe with thin nickel plating.
 
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