What do I need to know to plug my TV into my neighbour's antenna?
July 25, 2006 4:39 AM   Subscribe

What do I need to know to plug my television into my neighbour's rooftop television antenna?

My place doesn't have a television antenna on the roof so I use a small, crappy antenna. My neighbour's place has a rooftop antenna that the previous owners installed. To install an antenna at my place will cost more money than I have.

My place is one of a few townhouses made from a much larger house. So, between me and my neighbour's place is a single wall. They have agreed to let me run a wire from their antenna to my house, providing I deal with everything.

Will doing this weaken their signal? How do I get around this? Are there any serious problems with this idea? If so, how do I get around them? What do I need to know?
posted by teem to Home & Garden (4 answers total)
You will be putting in a splitter at some point. It will weaken the signal downstream of an unpowered splitter, but hopefully it won't be a problem. A powered splitter should remove that chance of a problem.
posted by TheOnlyCoolTim at 4:54 AM on July 25, 2006

To avoid the possibility of weakening the signal, you probably want a gadget called a masthead amplifier, which amplifies the signal where it's strongest (at the aerial) and can also act as a splitter. The power for the amplifier runs up the aerial cable (presumably from your side). Any DIY-oriented hardware/electronics store should be able to sell you one.

You can also install either a masthead or a conventional amplifier lower down the chain if you don't want to get up on the roof, but the further away it is from the aerial the greater the loss.
posted by cillit bang at 5:27 AM on July 25, 2006

TV signals aren't like mains electricity wiring; you can't really get away with just stringing several sockets onto the one cable. You'll need a splitter, with three cables connected: one to the antenna, one to your TV, and one to your neighbor's TV.

As TOCT mentioned, splitters cause insertion loss - both their output signals are weaker than their input signal. So after you install the splitter, your neighbors will have slightly less signal than they used to.

TV's will automatically compensate for this kind of thing, by turning up their sensitivity; but if the signal was already marginal, this might not be enough. So there is some possibility you'll screw up your neighbor's reception by doing this.

If this happens, you can fix it by installing a masthead amplifier. This will make the signal entering the splitter stronger, and should give both of you better reception than your neighbor had originally.
posted by flabdablet at 6:27 AM on July 25, 2006

Licensed broadcast engineer here. Generally, masthead amplifiers are intended for situations where there is a long downlead required, and it is necessary to provide a higher signal level off the antenna to overcome the downlead loss; rarely will they improve the picture quality of a marginal antenna installation, because they (as simple broadband gain devices) rarely have lower internal signal-to-noise level specifications, than a television reciever (which is always a high quality tuned superheterodyne circuit) does. More often than not, inserting a broadband UHF mast amplifier makes for worse picture quality than better; you have to match amplifier components exactly to measured signal levels to achieve consistent improvements, although such devices do have their place in properly designed systems, with long downlead runs, or multi-set distribution systems.

A typical "two way" passive splitter of good design will produce a typical insertion loss of 3 to 7db, meaning each downlead after the split will be getting from half to 1/8 the absolute signal power of the unsplit line. If this reduction is significant (it may or may not be for installations in an urban setting within 10 miles of the broadcast tower), raising the antenna is the best way to get more signal strength. Absent that, you could replace the existing antenna with one of higher gain design.
posted by paulsc at 7:48 AM on July 25, 2006 [1 favorite]

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