Wiring up TV aerial

[Trowelblazer]

Hi,

I am currently renovating an old house and I thought while the scaffolding was up I would sort out the tv aerial. There is currently a decent aerial on the chimney and it is pointing in the right direction but the old cable has had it.

I will eventually be have a tv in three different rooms in the house but need some advice on the best set up for the aerial cable, is it best to use a splitter or will I need a booster? Are there any alternative set ups I can use?

Thanks

 

[Lucid]

The two solutions are (1) a passive splitter which is an unpowered split, or (2) an active splitter. This is probably what you're thinking of when you wrote "booster".

In terms of signal purity then a passive splitter is best. It introduces very little if any signal noise so the Signal Quality stays high but you do lose signal power (Strength) because splitting means dividing the signal 4 ways in your case. There are area couple of things to watch for though. First, you have to have a very strong signal across all of the channel range being used now across the range that is proposed to be used in the future. That's not an easy thing to gauge as a DIYer.

Second, a passive splitter needs to be fitted as far from the roof aerial as possible. This is different to how you would use an active splitter which would either be on the aerial mast or in the loft which means it is relatively close to the aerial.

The times when you would choose an active splitter are where the aerial signal is strong enough to run 1 or 2 TVs via a passive splitter but not strong enough to withstand the losses from splitting 4 ways on top of the losses as the signal travels down cable to the TVs.



Where you would avoid using an active splitter is when there's very strong signal direct off the aerial (the result might be too much signal power at the TVs), or where the signal quality is already marginal. Amplified splitting adds noise, and noise reduces signal quality rather than improving it.

For DIY install without the benefit of metering to look at Quality and Strength across the entire signal spectrum on site the active splitting is probably the simplest route. If you find that there's too much signal strength at a TV then it's possible possible to fit an attenuator to that TV and reduce it.

Cable. Don't waste your money on the cheap RG6 crap from the DIY stores. Buy Buy a reel of WF100. It's the best stuff to use and not expensive when you figure it will last twice as long or more outside.

 

[Sam Gangee]

More reading: http://www.satcure.co.uk/tech/cable.htm
and http://www.satcure.co.uk/tech/amps.htm

For more specific advice, please state the postcode and current type of aerial.

 

[winston1]

If you find that there's too much signal strength at a TV then it's possible possible to fit an attenuator to that TV and reduce it.

If the signal is too strong at a TV then it will be too strong at all of them and the amplifier may be overloading. Better to fit the attenuator before the amplifier, but in this scenario I would be replacing the amplifier with a passive splitter.

 

[Trowelblazer]

Thanks for the help. I appreciate the advice

 

[SimonH2]

I would suggest two places to go and look.

Wolfbane's reception predictor, that'll tell you want RF channels are in use now, and what you need to receive them.

UK Free TV info where you will find information not just one what you can get now, but what changes are planned. This has a big impact on what you install now. For example, where I am, I get Winter Hill using either a wideband or Group C/D aerial - but in a few years it looks likely that it'll be changing such that I;d need a Group A aerial.
So I have to decide - do I use a wideband (eg Log36), or a high gain Yagi and accept that I'll need to replace it in a few years. I'm leaning towards a Yagi myself as it's not too hard to get to (for a pro) - but if it would need scaffolding then you need to think long term.

But above all ... Get a good quality antenna, use good quality cable, wire it up properly, fix the cable properly, and use a good dose of corrosion inhibitor - I tend to smother everything (terminals, screw threads, everything) in vaseline as I assemble it. And throw away any "wing" nuts, and use decent nylock nuts instead that you can tighten with a spanner.

Another really really useful site is http://aerialsandtv.com (it's where i go for my aerials) - there's a wealth of information on there. Have a good read, especially the Cowboy's Locker pages which are good for a laugh

 

[Sam Gangee]

I've always used silicone grease, which is very water repellent and doesn't oxidise as Vaseline does (goes brown). And, again...

For more specific advice, please state the postcode and current type of aerial.

 

[ey143]

Cable. Don't waste your money on the cheap RG6 crap from the DIY stores. Buy Buy a reel of WF100. It's the best stuff to use and not expensive when you figure it will last twice as long or more outside.

I'm in a similar situation, gutting out house etc.
The WF100 cable that you refer to, is the tough cable that the likes of Virgin Media install? If so, how flexible is this cable to use inside the house between a amplified splitter in a loft room to say 5 or 6 other rooms around the house? Can it be used for all A/V devices?

 

[Sam Gangee]

Virgin does NOT use WF100 cable. They use something tougher that can be laid outdoors. WF100 is usually flexible enough but if you want really flexible cable, look for WF65 (twin) or WF65-1 (single) but bear in mind that it has double the signal loss of WF100. Choice of cable is always a trade-off. Both types of cable are OK up to more than 2 GHz so obviously they are fine for low frequency audio and video applications (wherever 75 Ohm cable is appropriate).
See my "More reading" link, above.

 

[Lucid]

I'm in a similar situation, gutting out house etc.
The WF100 cable that you refer to, is the tough cable that the likes of Virgin Media install? If so, how flexible is this cable to use inside the house between a amplified splitter in a loft room to say 5 or 6 other rooms around the house? Can it be used for all A/V devices?

The stuff Virgin Media uses is a triple shielded cable made by Webro. It is called HD100. The extra shielding and the cable's overall diameter is partly what makes it so inflexible.

WF100 coax is double shielded. It has a foil- and a braid- shield layer. This is more flexible than HD100 but a lot less flexible than simple and poorly shielded audio cables. Foil is used as a shield material because it is good at blocking interference at the high frequency (short wavelength) end of the radio spectrum. However, it isn't so effective with the longer wavelengths typical with audio. In fact, it's true to say that at those frequencies that foil is pretty much useless. A large part of the reason for that is the resistance of the foil. It is a poor conductor. This is an important point. The way shielding works is to divert the energy from interference and drain it away to earth. Foils don't do that so well because they're a much poorer conductor than braid. The material too is important. Cheap coax cables (e.g. RG6) use a plastic tape covered in a thin layer of aluminium as the shield. This is commonly known by the trade name of Mylar. Compared to copper, Mylar is more flexible (and a hell of a lot cheaper) but a far less effective shield material due to the much higher resistance. The braided wire shield does the job of earthing the cable to drain the interference. Once again the material choice has a big effect on the performance. Copper and Tinned Copper braids are significantly better conductors than aluminium because they have much lower resistance. Once one has dealt with the type of material it's then down to the effect of "how much" material. Just like fuse wires get thicker the more current they have to deal with, then braid becomes more effective at earthing the more dense the weave becomes. Very high density weave cables, especially those with a double layer of braid, are highly effective at dealing with interference across the video spectrum. The rub is weight and cost.

WF100 will be fine electrically for the video side of AV work for connections requiring composite video, Component and RGB. Mechanically though you might have to think carefully about cable routing and the length required to get a gentle enough radius to bend the cable without kinking it.

For audio interconnects there are better choices. This is very good because it has two layers overlapping of high density braid Link