Coaxial Cable Questions

[Bobballs]

I have a TV point in my back room that is fed directly from the coaxial cable coming from the outside ariel. I have a second ariel point in another room that is fed off the first ariel point the second ariel point is fed by another piece of coaxial cable from the first ariel point to the second.

The second piece coaxial cable feeding the second point has its main core pushed into the main part of the first socket so its side by side with the main core off the main coaxial feed, the wire mesh from both coaxials cables has been twisted together and screwed into the part of the ariel socket this goes to, should this work ?

At the moment the second ariel point is not working after I fitted a new ariel socket (the socket is fine tested), Im not sure if its something to do with the coaxial setup I have ? Would having any of the mesh bit touching the main core break things ? Or would having both the cores touch break things ? Also would a kink in the coaxial break things I think there may be a kink in the second peice of coaxial but I can't access it.

Cheers

 

[ChrisFrost]

This kind of looping between the sockets is an accepted way of wiring in a single room. There are sockets with 'in' and 'out' connections marked on the back for this very purpose. It works so long as a TV or recorder is plugged in to only one of the sockets at a time.

The core and the braid need to be kept separate. Core to core is good. Braid to braid is good. Core to braid is bad. If they touch then you'll get interference.

You said you have tested the socket. Does that mean you have a meter? If so then you can do a couple of simple tests to check the cable integrity of the non-working extension. You want to test for shorts and for continuity. If the cable is good then the problem lies with the connections at one end of another.

 

[Bobballs]

This kind of looping between the sockets is an accepted way of wiring in a single room. There are sockets with 'in' and 'out' connections marked on the back for this very purpose. It works so long as a TV or recorder is plugged in to only one of the sockets at a time.

The core and the braid need to be kept separate. Core to core is good. Braid to braid is good. Core to braid is bad. If they touch then you'll get interference.

You said you have tested the socket. Does that mean you have a meter? If so then you can do a couple of simple tests to check the cable integrity of the non-working extension. You want to test for shorts and for continuity. If the cable is good then the problem lies with the connections at one end of another.

Thanks Chris, the looping sockets you mention with an IN and OUT do you know where I can get one ? I've had a google can't find one.

When I tested it I moved the TV from room to room so only 1 socket being used at at a time. As for testing the socket, the second socket that wasnt working I took off and put where the first socket was and it worked so thats what I meant. My worse fear is the coax cable to the second socket is damaged under my new floor somewhere, I don't have a meter to test this though, all I can do at the moment is use the tv to test it, is there any other easy way to test it, can I only do it with a meter ?

 

[ChrisFrost]

I get my wall plates from my aerial wholesaler. I don't know what's available in the retail market. Have a look at the Satcure web site to see if they have something.

For cable testing you could rig up something with a torch bulb and a battery.

 

[ericmark]

I have in back of my mind de-coupling capacitors.

I am sure I could set up electronic workbench to test but not really inclined to work out how.

But you can't test an AC circuit in same way as DC and RF is AC. Put a coil of wire in a DC circuit or a capacitor and they show as conductor and insulator. However in an AC circuit one can arrange these components to allow one frequency and reject another. This is the whole idea of the tuning capacitor found on old radio's.

The wall plates come in many different flavours. Some are just basic connectors, some are designed to stop atmospheric voltage, and some have complete band pass filters and can combine and split radio, DAB, TV and Satellite. They also reduce interference from other sources like radio hams.

Testing coax alone with a standard multi-meter may find a fault connect to inner and outer one end then short and open circuit other end and you should see meter respond accordingly. But once connected to plates this is not the case.

The coax is in essence a load of inductances and capacitances along it's length and it possesses an impedance with amateur radio normally 50 ohms and TV more like 75 ohms and computers around 95 ohms you can't measure this with a normal meter but impedance matching is very important. Fill an air spaced coax with water and the multi-meter test may show no fault but the impedance can be well out of speck and the cable is useless.

Although it can be tested where one is suspects the cable may be faulty easiest course is normally to replace it.

Do also remember a Yagi beam will show short circuit. It is hard to get the impedance of a Yagi much better than 25 ohms so normally they have a balum or some other matching device so it is hard to predict what results one would get from using a multi-meter.

Most of my aerials are used for transmitting on, and if not correct it will reflect the signal so a simple voltage standing wave meter will tell me state of aerial and lead. However with the very low signals received with TV aerials it is very hard to measure directly it's condition. Hence what I said before normally renew and see if that improves it.

 

[Bobballs]

I get my wall plates from my aerial wholesaler. I don't know what's available in the retail market. Have a look at the Satcure web site to see if they have something.

For cable testing you could rig up something with a torch bulb and a battery.

Thanks Chris and Ericmark.

Its only some of the time I am going to be using the TV in the other room where I cant seem to get reception at the moment. Given that I can't find a wall plate with an in and out would I get a way with a double ariel socket like this, http://cgi.ebay.co.uk/Double/Twin-C...vr_id=&cguid=6ff8a5581260a0aad0d24062ffc89d7e

I would put the first bit of coax into the first socket and the second bit of coax feeding the other room on the second socket of the double socket, then when I want to use the socket in the other room I just put a bit of coax between the two sockets on the double socket ?

If it comes to it and I need to replace the coax cable the problem I have is I dont want to lift the floor, I was thinking may I could connect the new piece of coax to the old coax cable and pull the old cable out and that should feed the new coax cable through do you think thats do-able I'm sure Ive seen tools for such an operation.

 

[ChrisFrost]

Its only some of the time I am going to be using the TV in the other room where I cant seem to get reception at the moment. Given that I can't find a wall plate with an in and out would I get a way with a double ariel socket like this, http://cgi.ebay.co.uk/Double/Twin-C...vr_id=&cguid=6ff8a5581260a0aad0d24062ffc89d7e

I would put the first bit of coax into the first socket and the second bit of coax feeding the other room on the second socket of the double socket, then when I want to use the socket in the other room I just put a bit of coax between the two sockets on the double socket

Yeah, that'd probably work.

If it comes to it and I need to replace the coax cable the problem I have is I dont want to lift the floor, I was thinking may I could connect the new piece of coax to the old coax cable and pull the old cable out and that should feed the new coax cable through do you think thats do-able I'm sure Ive seen tools for such an operation.

As long as the existing coax isn't trapped somewhere then that should work.

 

[Bobballs]

Its only some of the time I am going to be using the TV in the other room where I cant seem to get reception at the moment. Given that I can't find a wall plate with an in and out would I get a way with a double ariel socket like this, http://cgi.ebay.co.uk/Double/Twin-C...vr_id=&cguid=6ff8a5581260a0aad0d24062ffc89d7e

I would put the first bit of coax into the first socket and the second bit of coax feeding the other room on the second socket of the double socket, then when I want to use the socket in the other room I just put a bit of coax between the two sockets on the double socket

Yeah, that'd probably work.

If it comes to it and I need to replace the coax cable the problem I have is I dont want to lift the floor, I was thinking may I could connect the new piece of coax to the old coax cable and pull the old cable out and that should feed the new coax cable through do you think thats do-able I'm sure Ive seen tools for such an operation.

As long as the existing coax isn't trapped somewhere then that should work.

I tried everything with the cable but came to the conclusion the connection under the floor was loose, I wasnt going to pull the new floor though. In the end I got a video sender and digi box took 10mins to set up and manage to get reception in every room The video sender I got I was very impressed with 5.8ghz from Argos £54 plug and play http://reviews.argos.co.uk/1493-en_gb/9239827/reviews.htm

 

[winston1]

This kind of looping between the sockets is an accepted way of wiring in a single room.

RUBBISH. Aerial sockets should never be looped like this. If a TV is plugged into a middle socket there will be reflections from the open end socket causing ghosting.
The aerial feed should be split using either a passive splitter if there is enough signal or a distribution amplifier if not.