The
coax cable route works well but is limited in resolution. It is standard definition (SD) and basic mono audio regardless of whether the signal from Sky is SD or high definition (HD).
Budget/cheap Wireless Video Senders are also limited to standard definition. The signal connection port for them is either SCART or the yellow, red and the white phono sockets. Budget wireless senders range in price from £30 - £70
HD wireless video senders are available. The connection port is a HDMI socket, so you'll need to split the output from a Sky box to feed the TV and the HD sender. Prices range from £150 and up. Results with wireless senders are variable. The same product can work brilliantly at one house and terrible in another. The only way to find out is to try it. Be prepared for lots of hassle and returns.
If the distance involved is under 15m then a
long HDMI cable will probably work. There are situations where I have run HDMI at 1080p longer than that, but I have used good cable and the signal hasn't been split at the source end. If you're working from a normal Sky HD box (not a Sky Q box at 4K) then the signal will be 1080i. That requires far less bandwidth than 1080p, so it's possible you might get it to travel 25m without too much issue. You may run in to problems though if you watch 3D movies via the On Demand service. That requires about the same bandwidth as 1080p. All bets are off if you're using a Sky Q box at 4K.
HDMI Cat Baluns are nothing to do with Ethernet. The fact that they use Cat5 or Cat6 cable is purely coincidental. The baluns do not convert the HDMI signal in to IP, so the signal cannot be sent via an Ethernet switch. Forget any ideas about cheaply sharing Sky's signal via inexpensive HDMI baluns and the Ethernet ports on your router.... it won't work.
Baluns convert the signal in to a more robust form that can travel down twisted pair Ethernet (Cat) cable. That's about it. There's a range of prices in baluns. Some of that difference is due to whether the baluns send the signal in uncompressed form; IOW better baluns give out what you put in so the resolution isn't affected. I have come across cheaper baluns that resample the signal (reduce the resolution) so that it will either travel further or will travel via a single Cat5 cable. You need to check that out before committing to buy. The rest of the price difference is to do with the range they'll support, and whether they include IR signal return, if they handle EDID memory, and then there's marketing. Some baluns are the same product sold under different brand names.
The advantage of baluns is range. A good running on a decent pair of Cat5 or Cat6 cables might work happily up to 50 or 75m. The same signal travelling by HDMI cable might struggle to do 20m.
HDbaseT baluns. These look like simple Cat cable baluns but there's a couple of really important differences. The first is that they're designed to work with simple Cat5 cabling, and often with just a single cable rather than a pair as with a lot of the basic HDMI Cat baluns. The second is that a lot of the decent HDbaseT baluns can be used with an Ethernet switch. That doen't mean you can mix these baluns with your internet connected devices through the same router. It is best practice to run a separate Ethernet switch for these AV devices and leave your wired and wireless connections to run in a separate system so that the two never come in to conflict. HDbaseT baluns used to be prohibitively expensive (£400+ per pair) but increasing competition and growing sales volumes is helping to push prices down.
Now let's talk about control....
All of the options listed above include variants that allow IR signals to be sent back down the wire to control the Sky box from the bedroom. With HDMI cable you can attach add-on IR Injectors which look like a little extension plug for each end.
If you have an Android or Apple iOS smart phone and your Sky box connected to your Wi-Fi router then you can use your phone to run the Sky+ App. This will let you control all the play/pause/rewind features of your Sky box.
What else do you need to know....
A big trap that people fall in to is buying cheap Ethernet cable. Unless you know what to look for it's easy to get stitched up with Copper Coated Aluminium (CCA) cable rather than the pure copper stuff. CCA is cheap because it uses an aluminium core with a thin anodised coating of copper. That's a problem because aluminium is a poor conductor compared to copper, so baluns won't have their advertised ranges. The second issue is that aluminium is fragile. It breaks easily if the cable is bent or pulled too hard or stood on. It also makes putting on the network plugs a complete PITA. It is possible to break a wire when crimping the plug, so you then have to start again.
CCA also rears it's ugly head in HDMI cables too. Have you ever wondered just how some Ebay seller or Amazon can sell a HDMI cable, pack it and pay for postage and still make a profit out of a £1.99 sale price? That's because what you're buying is
this stuff and not 100% copper conductors.
Hope that helped. Hit the Like button if it did, thanks.