Coaxial Cable Antenna Lead-in Protector Theory Of Operation

[I-learns]

For my studies please. I haven't been able to get a clear theory of operation for antenna lead-in protectors used on coaxial cable. I think all the manufacturers want to say the basic operation of their product is proprietary. Can someone tell me if my understanding here is right? If so, have you seen a manufacturer or authoritative publication that actually explains it well? Most electrical education programs just explain that they are required, where they are to be installed, and maybe a basic of that they protect from strikes. They don't explain how they do this.

 

[LarryFine]

I've always been under the impression that they merely contain a spark gap.

 

[tom baker]

Did you look at polyphaser information?

 

[egnlsn]

The Datasheet can be found at:

https://tiitech.com/wp-content/uploads/datasheets/coax-protectors/210_212.pdf

 

[cadpoint]

Is this what's sitting outside in the side of the house? If not wear is it installed ?

 

[I-learns]

Is this what's sitting outside in the side of the house? If not wear is it installed ?

These would usually be installed outside of the house. I think they are allowed to be installed inside nearest the point of entry but usually it’s outside.

 

[suemarkp]

The shield of the coax is always connected to ground via this protector, since the in and out threads and GEC lug are all the same metal. The coax center conductor in some protectors gas a glass spark gap capsule that shorts to ground above a certain voltage.

 

[Hv&Lv]

gas discharge, gap, DC blocking capacitors in all arrestors, or some arrestors.
Depends on what you want it to accomplish.

DC Pass, DC Block Lightning Arrestors? - Communication & signal processing engineering

I use lightning arrestors between radio antenna and transceiver, like Andrew APG-BNFNF-350, for marine radio equipment such as VHF, MFHF, UHF, GPS. I understand that DC block lightning arrester is to block DC frequency interference, but there is likely no DC interference between matched radio...

www.eng-tips.com

 

[LarryFine]

The shield of the coax is always connected to ground via this protector, since the in and out threads and GEC lug are all the same metal.

It could be made with a gap between the can and one end's threads. Think of an AAA battery case.

 

[hbiss]

It could be made with a gap between the can and one end's threads. Think of an AAA battery case.

Read:

Tii’s patented proprietary coaxial gas tube surge protector is equipped with an integral failshort mechanism for a power-cross condition which shunts both the coaxial cable’s center conductor and sheath for a common path to ground. The DC breakdown voltage of the protector provides superior protection against transient surges, yet is compatible with network powered applications.

So, the center conductor is straight through with a gas tube protector to ground. And, no, the shield is continuous also. It will pass power through to devices if used that way.

-Hal

 

[GoldDigger]

The description in the photo suggests that there is indeed a gap in the metal shell isolating the inside end, and the needed ground continuity for both RF and DC is provided by an unspecified network that isolates the threaded end while a discharge to ground event is happening.
I have no speculation on what that might be. Earlier lighting protection only provided a gas discharge from the center conductor to the grounded shield. But the photo suggests an insulating insert between the threaded end and the can.

Sent from my Pixel 4a using Tapatalk

 

[synchro]

Here's a presentation about the surge protector shown in post #1 by the CTO of the company that makes it:

https://www.gcscte.org/presentations/2004/Grounding_and_Bonding.pdf

 

[GoldDigger]

Here's a presentation about the surge protector shown in post #1 by the CTO of the company that makes it:

https://www.gcscte.org/presentations/2004/Grounding_and_Bonding.pdf

Looks like the text in diagram in Post 1 is a product of Marketing rather than Engineering.

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[I-learns]

It could be made with a gap between the can and one end's threads. Think of an AAA battery case.

Yes that’s what I wondered. I’ve never had a reason to look that closely but if you look at the photo, there does appear to be an insulating ring between the body of the protector and the threaded court for the customer side connection. This would give the indication that perhaps for protection of equipment in some cases they are making ones that will disconnect if there is a high voltage event due to a nearby lightning strike.

 

[hbiss]

The description in the photo suggests that there is indeed a gap in the metal shell isolating the inside end, and the needed ground continuity for both RF and DC is provided by an unspecified network that isolates the threaded end...

No. Look at the Theory of Operation posted by @synchro.

There are isolators that do exactly that though- isolate the shield of the cable on the utility end from the shield of the cable going to the customer's equipment. They look exactly the same, though I don't think they provide any surge protection.

-Hal

 

[I-learns]

There are isolators that do exactly that though- isolate the shield of the cable on the utility end from the shield of the cable going to the customer's equipment. They look exactly the same, though I don't think they provide any surge protection.

-Hal

So for the ones that are listed as antenna lead-in protectors and required by the NEC, which one are they? The surge protectors that clamp and thus limit voltage between center conductor and shield; or the isolators that isolate the customer side of the shield when high voltages are seen?

It would seem the ones that clamp the center and shield would protect the coax equipment better; while the isolators would better protect the house from both fire and destruction of other electrical equipment (other than the coax equipment) from damage when a strike discharges through the house’s distribution system rather than its GEC system.

Didn't think this one would be a hard one. Wonder how many are done right!

 

[hbiss]

The NEC doesn't require any surge protection for a coax cable drop or antenna lead-in. All that is required is that the shield of the cable be grounded as close as possible to the point where the cable enters the premises. A simple ground block will suffice which is used in 99.9% of cable installs. Will it protect better than those other protectors? If the cable companies thought so they would be using them. Not our problem though because its mostly protecting their equipment. So, if a cable box gets blown up call them and they replace it.

-Hal

 

[Hv&Lv]

The NEC doesn't require any surge protection for a coax cable drop or antenna lead-in. All that is required is that the shield of the cable be grounded as close as possible to the point where the cable enters the premises. A simple ground block will suffice which is used in 99.9% of cable installs. Will it protect better than those other protectors? If the cable companies thought so they would be using them. Not our problem though because its mostly protecting their equipment. So, if a cable box gets blown up call them and they replace it.

-Hal

View attachment 2560874

One issue I had with cable company equipment was the lack of protection on their part.
Burnt out two of my HDMI ports on the TV before I had them remove the signal booster.
Still never took responsibility…
Got rid of spectrum and have a Roku on the last HDMI port available..

 

[hbiss]

One issue I had with cable company equipment was the lack of protection on their part.
Burnt out two of my HDMI ports on the TV before I had them remove the signal booster.

That's interesting. I can't see how a "signal booster" would have anything to do with what you are talking about. Damage to the TV is usually caused by the cable ground from the pole or pedestal carrying a surge or current back through the TV to the receptacle ground, (a ground loop). This is exactly the reason you would want to use an isolator as I mentioned above. It separates the grounds where the cable enters the house. Lightning and surges stay outside. Your cable in the house is grounded to your service ground which is the same as your receptacle grounds.

-Hal

 

[GoldDigger]

That's interesting. I can't see how a "signal booster" would have anything to do with what you are talking about. Damage to the TV is usually caused by the cable ground from the pole or pedestal carrying a surge or current back through the TV to the receptacle ground, (a ground loop). This is exactly the reason you would want to use an isolator as I mentioned above. It separates the grounds where the cable enters the house. Lightning and surges stay outside. Your cable in the house is grounded to your service ground which is the same as your receptacle grounds.

-Hal

And your circuit board ground in TV should be tied to its EGC. But all of those together still do not assure that all of your electronics stay equipotential in the event of a lightning event.