Grounded cable (TV)

[SavannahLion]

OK, so we were having problems. Cable guy comes out. Finds an exposed line. Fixes it. Problem solved. Short story.

During the process he finds that our house doesn't have a grounding block. The last guy who owned the house swapped it out for a splitter and tied the grounding strap to that. Cable guy says that's bad and reinstalled the proper grounding block.

I did notice the lack of the grounding block when I first moved in but, incorrectly, assumed the grounded splitter was suitable, and thus didn't bother fixing it. Whether installing the grounding block fixed our problem isn't clear, we had an exposed line that had been there for some time.

I understand the role the grounding block does (I think I do), I just don't quite understand why the splitter isn't a good substitute.

Attached photos are for clarity. They're not the exact brands that were used, just there for clarity.

[ed12]

the grounding block
makes sure u are at zero
the splitter even though it has a lug has no way to prove u are at zero

ed

[SavannahLion]

the grounding block
makes sure u are at zero
the splitter even though it has a lug has no way to prove u are at zero

ed

Well I understand the purpose behind the grounding block. To provide a path and reference to ground.

 I just don't understand what's missing from the splitter. AFAIK, the outer shell of the splitter is tied to the outer sheath of the cable.

[ed12]

outside housing have proven to become lose
ie no path

ed

[SavannahLion]

outside housing have proven to become lose
ie no path

ed

Really? The ones I have seem pretty sturdy. But you're right, the block does seem much more sturdy in construction.

[MonMotha]

It depends on the construction of the splitter.  Many of them are a "unibody" type thing.  There's no feasible way for the shell of the splitter to become detached from the outer shield conductor of the coax connectors on most of these designs since it's all one contiguous hunk of metal.  However, as this is not the primary function of a splitter, it's not a "guaranteed" thing.  Some cheap ones are built differently.

The grounding blocks, being as their only function is to properly ground the cable, "guarantee" this.  They generally provide a better (heavier, firmer) connection, too.

The materials also can differ.  Some (again, usually cheap) splitters have a case made out of "pot metal".  The conductivity and physical durability of pot metal is impossible to determine ("Hey I've got some metal."  "Cool, throw it in the pot!").  While it may be a continuous physical connection, the electrical properties can be fairly unknown, and the physical reliability suspect.  Note that this also is a bad thing from the POV of the electrical operation of the splitter, so higher end splitters may be made out of better metal.

Ground blocks are designed to be weather resilient and provide a electrically and physically solid connection over a long time.  Keep in mind that if the ground connection broke, you might not notice until you got zapped by lightning since the TV signal may keep operating as intended through the splitter.

Honestly, you were probably fine, but there's little doubt a real grounding block is less likely to have problems...and with lightning and such, chances are bad things to take.

[TOK]

The splitter contains components that won't take a surge. The theory behind the separate block is that you divert the surge before it hits the splitter.

A cable ground is strictly a passive thing... Having it grounded to a splitter, ground block or no ground at all doesn't affect the quality of your service.

[Ed_McCarron]

Re -- those ground blocks.  They only ground the shield, correct?  What happens if a surge hits the center conductor of the coax?

Or is the concept that 'the lightning just jumped 3 miles from cloud to earth -- it'll conduct across the 1/8" of dielectric in the coax?)

[MonMotha]

In general, the lightning would have to cross the shield onto the center conductor to start with (which it could easily do).  At the power and potential (voltage) levels of lightning, you can pretty much treat that hunk as a single conductor.  It'll easily break down the dielectric.  Anything that can cross that grounding block should at least be something that isn't overly dangerous to humans (but could still be dangerous to electronics), which is the primary purpose of that grounding block wrt lightning protection.