It cannot be THAT hard!!

[Greenie9657]

Hi ALl

Ive come here with this problem as a last resort as im pulling my hair out trying to think of why its happening and I cant explain but here goes:

Im in the process of wiring up my house as I go through each room, various posts on here would tell you the full story, anyway.... Ive put a coax point (duplex tv/fm modular outlet) in the front room and ran the coax (WF100) from the back of it up to the attic. (before I did this I just had an aerial on my roof with a coax straight into my living room, no plate or anything). With me so far...

Right, I just thought id test it before running into my attic, and low and behold, no picture. This is where it gets jedi....


If I put the original tv coax straight from the aerial into the back of my telly, picture is fine. If I put the coax from the aerial into an extension lead (would have used this to connect my tv to the wall with the new install) picture is fine, as soon as I connect the attic end of my coax to the aerial coax and the wall plate end (plate now removed) to the extension lead to my tv, no signal.

Ive resistance and continuity checked all leads, the lead ive put in the wall has 0 ohms on the centre conductors and like wise on the outer, there is no continuity between inner and outer (which is good). As soon as this coax (my install) is put into the equation, the signal goes.

Does anyone have any clue has to why this is?

Im pretty good with aerials, wires, multi-metres, electric testing etc but this one has really stumped me. I have no explanation.

Many thanks and I hope it makes sense

 

[cajar]

Could be a poor fit /mate on the wall plate outlet? could check this by adding a fly lead to the wall plate downstairs and recheck continuity.

 

[Sam Gangee]

This symptom can occur if the cable is crushed at some point. Can you check it visually?

 

[Greenie9657]

There's no where for it to crush as it's a nice big loop out of the wall and up the side of the house. If it was crushed though wouldn't I get more than 0 ohms? All the outer and the inner is still open circuit so nothing touching there either.

As for the fly lead, I've added one earlier and re-checked continuity and it's still 0 ohms.

Thanks for your help but I tell you, this is a right head scratcher!

 

[Sam Gangee]

Coaxial cable has to be coaxial. If someone bashes a clip too hard, the cable will be kinked/crushed and, even if the outer sheath springs back into shape, the internal dielectric will be damaged. The result is an impedance mismatch that won't show up with a DC measurement but can block RF signals. Feel the cable carefully along its length for any 'softness'.

Other than that, it has to be a connection fault.

Oh, it might also be stretched or (and I've never come across this) have a manufacturing fault - but I can't imagine what sort of fault could block the signal without any visible evidence of damage.