Feeding off an existing cable for digital terrestrial?

[badboy81]

I am living in the UK and I do not currently have a connection for an external aerial for digital (DVB-T) television (an aerial on the roof). I cannot afford to have one installed. However, one of the neighbours in my block of flats has said that I can feed of his aerial -- the coaxial cable for it passes by my window.

How do I feed off this coaxial cable without affecting his signal, which is used for both analogue and digital TV reception?

Is it enough to use a splitter, or will this make his connection worse? I already have a coaxial splitter, which splits one connection into two. But it was designed for CATV - it is a Tratec ES-02/MS and gives two 3.7dB outputs **broken link removed**. It says that it handles 5-1000MHz, and I think that analogue and digital terrestrial are both within this range. So will it be a problem to use this splitter?

Thanks in advance for any advice!

 

[Nigel Goodwin]

Splitting your neighbours signal WILL affect his signal, however, as long as it's good and strong it shouldn't make any real difference. If it's NOT good and strong then the drop will be very noticeable, with noisey pictures for analogue, and blocking and freezing for digital.

I'm presuming you are in an area that can get terrestrial digital?.

If you think about it?, it's pretty obvious that splitting the signal two ways sends half the signal to each set - in practice it's actually worse than that, due to losses in the splitter - the splitter has to maintain the correct impedance to prevent even more loss!.

 

[RadioRon]

If you insist on trying this, you would probably want to use a high performance splitter, one that is rated to 2.5 GHz. One way to make up for splitter losses is to include a low noise preamp in line before the splitter. This is something you definitely don't build, you buy it. I'm not familiar with the cable signals from this particular antenna, but I assume they are not downconverted at the antenna, which means that the preamp has to be a very good one with wide bandwidth up to 2.5 GHz also. It should have a noise figure of less than 2 dB, and a modest gain, perhaps about 8 to 10 dB. The gain is enough to make up for the splitter losses which will be around 4.5 dB, and a bit more to help maintain the noise figure of the system, but not so much that you risk overdriving the receiver with too much signal. If you want to learn more about this "noise figure" thing, just ask.

If the signal is downconverted at the antenna, then you can probably relax the bandwidth of the preamp and splitter, but you will probably still want the preamp.

 

[badboy81]

If you insist on trying this, you would probably want to use a high performance splitter, one that is rated to 2.5 GHz. One way to make up for splitter losses is to include a low noise preamp in line before the splitter. This is something you definitely don't build, you buy it.

How would I get hold of these? I searched google but all I got was the usually standard splitter fare.

 

[Nigel Goodwin]

If you insist on trying this, you would probably want to use a high performance splitter, one that is rated to 2.5 GHz. One way to make up for splitter losses is to include a low noise preamp in line before the splitter. This is something you definitely don't build, you buy it.

How would I get hold of these? I searched google but all I got was the usually standard splitter fare.

He's somewhat confused, as he's not in the UK, so he's talking about SATELLITE and not terrestrial.

You can buy powered splitters for UHF/VHF signals, they plug in the mains, have an INPUT socket and two (or more) OUPUT sockets, you simply plug your incoimg aerial lead in the input socket, and take feeds from the outputs to your TV's. There's a preamplifier in the splitter which boosts the signal before it's split, making up the losses - in fact they usually give a very slight gain overall.

You can buy them at any TV shop, electrical store, or even DIY store.

Obviously, as it's powered, it MUST be permanently powered up, or your neighbours TV won't work!. They only cost pennies a year to run.

 

[RadioRon]

Quite right Nigel. Terrestrial signals should be fine with the more readily available 1GHz rated splitters such as you suggest.