Which TV aerial goes where?

[dk1uk]

Hi - I have a TV amp in my loft connected to the TV aerial mast. There are four TV outputs running from that amp to various rooms in my house.

Can anyone think of an easy way of working out which cable leads to which room (without my having to use a process of elimination and moving a TV from room to room)?

I saw this posted on a website "...if you`re up in your loft trying to work out which cable has come from which room, try temporarily shorting out the cable and then checking which cable is then short at the other end with a multimeter."

I have a multimeter, but I don't know how to temporarily short out the cable, nor what setting to have my multimeter on and what reading a shorted cable would give?

The reason for the question, is that there's a TV booster in one of the bedrooms supplying power to the amp in the loft. Someone has kinked that cable and I suspect it's to blame for the interference that I'm getting on digital TV. So, I want to use a different socket for the booster to test whether indeed it is the kinked cable causing the problem.

Be grateful for any advice.

Thanks

 

[Sam Gangee]

To short a coaxial cable, simply connect the braided copper screen to the inner copper wire. Before you do this, make sure there's no power supply sending a voltage up it!

To measure for a short, use the test position marked with a diode. This will indicate zero when you touch the probes together and will often make a high pitch tone, too. Coaxial cable (e.g. WF100) has a return resistance of less than 0.05 Ohms per metre (or 0.5 Ohms for every 10 metres). However, your diode range won't give an accurate resistance reading. If you want that, switch to the lowest resistance range.

It doesn't matter which way round you connect the black & red probes for this measurement.

You might find this useful:
http://www.The-Cool-Book-shop.co.uk/electronics.htm#multimeter

 

[dk1uk]

Great - thank you for this.

 

[maltaron]

It is risky depending on a short circuit for locating cables, there could be a short in the cable!. The best way is to fit a resistor of any known value to a coax plug and use the meter on suitable ohms range.

 

[Sam Gangee]

Good point but obviously you check that it no longer measures s/c when the short is removed.

 

[ChrisFrost]

Good point but obviously you check that it no longer measures s/c when the short is removed.

This .... simple & effective.

I'm reminded of the early days of space exploration. The Americans spent millions of dollars developing a ball point pen that could write in zero G conditions. The Russians took a pencil. lol

 

[Sam Gangee]

The other point about checking with a short circuit is that the resistance measurement shows up any bad connection along the way.

I'm not knocking the resistor idea but the s/c method has other advantages.

 

[Grizzly]

I'm reminded of the early days of space exploration. The Americans spent millions of dollars developing a ball point pen that could write in zero G conditions. The Russians took a pencil. lol

A nice story, but mostly an urban myth, I'm afraid.
http://www.scientificamerican.com/article.cfm?id=fact-or-fiction-nasa-spen

 

[ChrisFrost]

A nice story, but mostly an urban myth, I'm afraid.
http://www.scientificamerican.com/article.cfm?id=fact-or-fiction-nasa-spen

Never let the truth stand in the way of a good story lol