Cable TV cable: how (via VOM?) to tell if has signal or not?

[David Combs]

We've recently rearranged room-use in the house.

Where the tv now is, there is cable extension-cord supposedly bringing the signal from the cable in a nearby room.

However, when attached (screwed onto) the working tv, there's no signal. (TV works ok, since tivo works just fine with pre-recorded programs).

QUESTION: Given a VOM (Volt-Ohm-Meter), how to detect the presence of a cable-tv signal on the cable?

(Of course, one, maybe the best, scheme would be to haul the TV itself around and try plugging (screwing) in the original NON-extended cable, but that would mean, as above, hauling a tv around, a pain. So, using just the VOM, how can I test the cable for a likely signal?)

Meaning what IS the standard voltage between the center wire and the cylinder of shielding?

(And I can of course UNscrew the extension cable from the original cable, and use the ommeter-part to check for (a) continuity between the two ends and (b) across one end, check for a short.)

Which a and b I will go do.

But what voltage, when there IS a signal?

And, AC or DC?

Thanks!

David

[Ralph Mowery]

A common vom will not detect any signal on the cable.

It is a broad band signal, actually a lot of signals in seperate chanels. Usually starts at several Mhz or more. You might call it AC but really is RF.

Looks like you have to drag a receiver around with you or do the ohm meter check.

[ps56k]

yeah - it's not like your normal "electricity" it's RF - so more like an "transmitting antenna" with a shield around it.

[David L. Martel]

David,

You don't need a VOM if you have a Tivo. Go into the "other room" and record something. Take the Tivo into the TV room and play that recording Got a tv program? Then there is a TV signal in the other room. No program means a problem with the tv signal in that room Now hook the extension cable between the other room and the Tivo. Record something. Play the recording into the tv. If you can watch the program then the extension cable is ok. If you get nothing the extension cable is bad. If the extension cable tests ok look at how you are wiring and setting up the tv. Something is wrong at the tv.

Dave M.

[hrhofmann]

Can't you follow the wire?? If you can disconnect both ends of the cable you think is continuous between the two rooms, you can connect the ohmeter between the inner and the outer conductors of the cable in one room. Then have someone short-circuit/connect the inner and outer conductors together at the other end of the suspect cable. If it really is the same cable, you should go from an open circuit to about

5 ohms or less when the far end is shorted.

[Mark Lloyd]

[snip]

It's nice to have a small TV you can carry around. I use a 7-inch LCD TV with battery.

[Ralph Mowery]

While I have not had to do, I have a converter about the size of a big old thumb drive. It plugs into the usb on a netbook I have. Should be easy enough to carry around from room to room. I do use it to watch shows off the air if the power goes out, or I am out where I need a portable set.

[trader4]

Another easy way would be if he has cable internet. Just take the cable modem to the location to be tested and see if it locks on to the signal, ie the indicator lights show that it goes online.

[ps56k]

just a little clarification please....

- where is the "original" working cable outlet - in the wall ? cable laying on floor ?

- what do you mean by "extension cable" ? again, is this inside the wall to a wall outlet, or a physical cable laying on the floor and running back to the original outlet and screwed onto the connector at that point ?

Just trying to get a mental picture of your layout, the cables involved, how they are physically routed, and "connected" together..

[jamesgang]

re is cable extension-cord supposedly bringing the signal from the cable in a nearby room. However, when attached (screwed onto) the working tv, there 's no signal. (TV works ok, since tivo works just fine with pre-recorded pr ograms). QUESTION: Given a VOM (Volt-Ohm-Meter), how to detect the presence of a cable-tv signal on the cable? (Of course, one, maybe the best, scheme would be to haul the TV itself around and try plugging (screwing) in the o riginal NON-extended cable, but that would mean, as above, hauling a tv aro und, a pain. So, using just the VOM, how can I test the cable for a likely signal?) Meaning what IS the standard voltage between the center wire and t he cylinder of shielding? (And I can of course UNscrew the extension cable from the original cable, and use the ommeter-part to check for (a) continui ty between the two ends and (b) across one end, check for a short.) Which a and b I will go do. But what voltage, when there IS a signal? And, AC or D C? Thanks! David

You can't measure rf with a vom. But you can check continuity. Short out one end and measure the resistance at the other end.

[David Combs]

yes, I did that. Extension cable ok.

Wife didn't want to disconnect tivo vcr tv etc to move tv to other room. Also even if we fixed, she didn't want any extension running from one room to another.

So we just called the cable company and they installed a new cable right next to the tv. $40 or so. And wife happy -- no visible cables!

David

[David Combs]

Sounds pretty darned easy!

Thanks!

[David Combs]

Original cable in a small bedroom.

Extension cable screwed onto it and run out the door and into another small bedroom (now office/tv-room), and screwed into working tv there.

Turns out that original cable was unattached at the splitter, to make place to attach another cable (some years ago, and forgotten).

Finally called in cable company; everything all fixed.

Thanks!

David

[David Combs]

end and measure the resistance at the

Yes, did do that. Well, not quite.

Got both ends together, checked continuity for inside, for outside shielding, and also checked for short between the two.

David