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Connecting it all up

Why are there so many sorts of connecting cables? Find out with this quick guide.

Why are there so many sorts of connecting cables?  Find out wit
published on UK Free TV

Why are there so many sorts of connecting cables? Find out with this quick guide.

The connectors on each cable are called plugs (and are also called male) and they will usually fit only into one sort of socket (or female connector).

Most cables you will come across are male to male. Occasionally you will find leads with a socket on one end and a plug on the other, and these are called "extension cables".


The SCART cable is used to connect a set-top box to a television set, or to a video recorder. This can only be a short cable. The SCART cable carries all of these types of signal:

  • analogue stereo sound
  • a single RGB television picture
  • a single composite video picture
  • a single S-Video video picture
  • widescreen picture signal

As stereo sound, RGB picture and widescreen signal is the best possible combination for digital television viewing, it is vital to use a SCART lead between any set-top box and the main television.

The composite video picture with stereo sound is the best combination for a VHS video recorder. If your set-top box has two SCART sockets, it is likely that the one marked TV will carry RGB picture information and the other will not.

If your television has more than one SCART input, you may need to choose a special one (marked RGB) if you want to use RGB from the SCART cable.

On most set-top boxes it is possible to turn the RGB output on and off. This can be used to test the RGB input function on the television ? the picture quality appears blurred when it is disabled.

If have a DVD player, rather than a VHS recorder, you can attach this to the set-top boxes second SCART connector. The signal from the set-top box will normally be overridden by the DVD player when it is on, usually in high-quality RGB.

Some very cheap SCART cables do not have all the pins connected. They may not provide RGB and widescreen picture signals. SCART cables are normally no more than three metres in length.

UHF lead

The UHF lead is a lead that you would traditionally associate with television signals. They can carry:

  • up to 45 (but normally only five) analogue television channels
  • a single picture from a set-top box
  • around 50 analogue cable TV channels
  • mono sound
  • NICAM stereo sound
  • Teletext services (for example, Ceefax)

You can't avoid these cables if you are going to use Freeview, as these cables are the only ones that you can use to distribute Freeview signals around the house.

Where you have an integrated digital television (an idTV) you just need to get the signal from the aerial to the television with one of these cables.

If you are using a Freeview set-top box, you will need to get the signal from the aerial to the set-top box using this aerial lead, but for best results connect the TV to the box with a SCART cable.

You can also use a UHF lead to connect a set-top box to a television somewhere in the house. Your set-top box will require a RF (radio frequency) modulator. Note that "RF passthough" is another way of saying there is no modulator. You will be able to "tune" the second television into the picture showing on the set-top box.

Some boxes (all Sky boxes) have the ability to connect a remote control receiver to the second TV end of the interconnecting cable, so you can change channels.

The set-top boxes, whilst providing a reasonable quality picture to the second TV, will always provide only mono sound via a UHF lead.

The step-change in picture quality obtained by switching to RGB on a SCART is far greater than any obtained though spending any more on a gold-plated SCART cable.

Satellite or cable TV cable

These cables are usually very stiff, and have a very basic screw connector on the end. Usually they will provide an unbroken link to the satellite dish. At the dish end they plug into the device on the end of the arm, the LNB.

Don't try to disconnect these cables when the set-top box is on. Usually there is a small voltage that will cause dangerous sparks.

If the cable connects to a satellite dish, there is not much you can do with the cable. Each receiver in the set-top box needs it's own wire to the LNB. With a personal video recorder (such as Sky+), or a multi-room installations there are two cables to the four-output LNB on the dish. If you want more rooms, each will require it's own cable.

If the cable is providing cable TV, then it is possible to use inexpensive "Y connectors" to link the incoming signal to various set-top boxes, cable modems, or - via an adaptor - directly to the back of a TV.

Composite video cable

This is the most simple and basic video connection you can get. It carries:

  • a single picture from a set-top box

The picture will be in colour, and of comparable quality to a analogue broadcast station. However, there is no sound. For that reason this cable is often found joined to a stereo audio cable.

These signals are quite robust and can be carried for many metres. Often modern television sets have a single yellow photo input on their front input panel.

You also use an identical cable to carry digital stereo (SPDIF) sound.

Stereo audio cable

These cables carry the left and right channels of sound on two joined cables. They are usually required when a SCART cable is not being used, as the SCART cable already carries stereo sound.

If you are connecting your set-top box to an external stereo system, a separate stereo audio is used.

There is no real practicable limit to the length of these cables, but excessive length will degrade the quality of the signal.

S-video cable

The S-video standard is not well supported by most UK digital TV boxes, and very few have a S-video socket. If you need one for a particular analogue camcorder, use it, but avoid S-video with digital television. If you are using what appears to be a monochrome picture from a SCART lead, it will certainly by an incomplete S-Video signal and you should change to the RGB input.

VGA cable

This is the cable you will use to connect a computer to a old style monitor, and some modern LCD screen too. Most modern LCD TVs will have a VGA input too.

If you want to connect a set-top box to a LCD monitor, you can buy a conversion box from around 60. However this will not result in a better picture than using an existing SCART socket if there is one.

The only way to get higher than normal television resolution is to use a VGA in conjunction with a personal computer or modern games console.

DVI cable

If you want to get the very best out of a television or monitor use a digital video interconnect (DVI) cable.

This will be the only way for most televisions and monitors to receive high-definition pictures from a computer, and some set-top boxes.

If you can use either a VGA cable or a DVI cable, choose the DVI option.

HDMI cable

If you want to get the very best out of a television use a HDMI cable.

This will be the only way for most televisions to receive high-definition pictures from set-top boxes.

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Wednesday, 27 March 2013

8:55 PM

Jim - I sell TV's part time, and legacy equipment is one of out biggest bugbears.

As JB38 points out, check that your existing equipment had HDMI's (DVD recorders often do), and whether you will be upgrading to Sky HD or Freesat(which of course uses HDMI). VCR's are now obsolete, and I would generally advise people to think 5 years ahead, not 5 years behind. You can get switchers, convertors, etc, but they are often a pain, and the cost is often not much less than a cheap Blu-Ray player, etc.

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MikeB's 2,579 posts GB flag
Tuesday, 2 April 2013
7:06 PM

I have the Humax PVR-9300T conncected to an old analogue tv via a scart cable and am about to purchase a new Samsung digital freeview tv with an hdmi connector.
My questions are, once connected to the Samsung via hdmi should I include a splitter into my aerial cable to feed both the tv and the pvr to get freeview on both independently, and enable me to still record programmes via both tuners on the pvr whilst watching a third programme via the tv freeview tuner?

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Norrie's 1 post GB flag
Dave Lindsay

7:13 PM

Norrie: You should be able to daisy-chain the PVR; that is, put the incoming aerial lead into the PVR and then connect the PVR aerial out to the Samsung TV. Or, of course, you may be able to use a splitter and turn off the RF passthrough on the PVR which means that the PVR no longer supplies a signal from the aerial out (because you're not using it).

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Dave Lindsay's 5,724 posts GB flag

8:47 PM

Norrie - I hate to disagree with Dave, but thats exactly how I have my system set up, and frankly, it makes life a lot easier.

My Sony recorder has never taken well to being passed through to my freeview box/CRT TV, and a decent spliiter (my original was free from the ariel guy, but £5.99 from Maplin should be fine, the same is even less online) and a second ariel lead is all you should need, and set them up as you suggested - simply put the splitter into the wall and attach the two leads to the TV and the recorder.

In fact one of the Samsung reps made up one for me from F connectors (he was a former TV engineer and said that F connectors are far better than normal leads anyway), and it works very well. The power of the Freeview signal went up tenfold following switchover, and splitting makes no difference to the quality of my signal, but does help in solving any reception issues, because you can isolate a possible problem very quickly, and I can use two seperate tuners.

The Humax is very good (simply pop in the HDMI cable and take away the scart), as are the current Samsungs, but I suspect that now you are able to watch HD, recording will be your next target, and the Humax YouView had proved to be very popular. That said, if you bought a 5 series Samsung upwards, the TV smart functions now allow catchup from all four channels.

I admit this method might not be 'offical', but it seems to work.

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MikeB's 2,579 posts GB flag

9:08 PM

Norrie: And just to add to that said, success when using a non-powered splitter is totally dependant on whether or not you reside in a good signal area as splitters of that nature always have a slight attenuating effect on the signal, and should this happen resulting in picture glitching etc, then a powered type has to be used as they provide each of the output sockets with exactly the same level of signal.

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jb38's 7,179 posts GB flag
Wednesday, 3 April 2013
Neil Bell

6:11 PM

Norrie I'd go with Dave first. A short aerial lead is all you need to daisy chain and then you can see if it works with the PVR switched on and watching an HD channel on the TV at the same time. If everything works problem solved. If not then a simple splitter may well not work either and you may need an amplifier as well. In the days before analogue switch off I found that a daisy chained DVD recorder and HD ready TV worked fine on a single output from my aerial amplifier but when I bought a TV with an HD tuner I had to run a separate cable for the TV to be able to watch HD progs on the TV at the same time as the DVD recorder was switched on. Of course the digital signal is now stronger so you may well find daisy chaining works.

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Neil Bell's 106 posts CZ flag

10:51 PM

In theory, passing a freeview signal through another bit of equipment basically does much the same thing as using a seperate splitter. Either way, provided you've got a decent signal, you should be OK, but looping through is recommended by the manual and is a little neater. My splitter has a 4Db loss.

However, curious as to what the reality would be I actually did a test in the name of science. I looked at the strength of the signal on my cheap Goodmans digibox with my present setup - around 70% on strength and excellent quality, so fine. I then unplugged the Digibox from the splitter, and connected it into the digital output from the Sony PVR. Admittedly the lead I used was a decent but cheapish flylead rather than the high rated coax its usually connected to, but the picture seemed no different.

When I looked at the signal strength on the Digibox, I was surprised that the strength had fallen to about 60-65% - still OK but the bar was now a slightly sickly green/brown rather than the full green before. This is hardly conclusive (might try with proper coax), but I did put the original setup back!

My best suggestion would be 'whatever works' - but use the best connections you can from the ariel to your equipment - spend slightly more on good coax and you'll get a better signal.

If you go to 7 Day Shop, you can get very decent 1.4 HDMI cables for £3.99 or less each (cheaper still with a multi-deal),and that should be fine. Instead of spending a fortune on HDMI's, spending £3-12 on a decent flylead (and any other analouge connects) will be money well spent.

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MikeB's 2,579 posts GB flag
Thursday, 4 April 2013

1:19 PM

MikeB: Regarding the issue of signal level differences being seen on a TV between when its aerial has been connected directly into it compared to that after having passed via a loop through facility such as on a PVR or HDD recorder, because although obviously some of these thin lower cost jumper leads can lead to odd problems being experienced, however in most cases these differences in levels are not being caused by this but by the circuitry associated with the loop through sockets, and with the reason being as follows.

In most PVR or HDD recorders or indeed any device with a loop through socket facility, the signal path from the aerial input socket does not pass in an electrical fashion directly over to the output socket but goes through a transistor buffer stage located between the input and output sockets, this being the reason why that any device that is being looped through has always to be kept powered (a few exceptions exist) because if it isn't then the signal to the TV or anything else on the end of the loop through will either drop or vanish altogether when the buffer stage transistor loses its power supply, although in real life situations a really strong signal might still partially break through resulting in a somewhat glitchy picture being seen, whereas when feeding an analogue TV all it usually resulted in was to witness the picture fading into a grainy background and not vanishing altogether due to the fact that analogue reception is not subject to minimum threshold cut off levels.

Obviously this loop through problem was thought about in the design of more recent boxes incorporating "power management" or "power save" options, this being the reason for allowing the user the choice of switching the system off, the latter being advisable so as not to miss any software updates that might be in the offering.

By the way, the reason for the buffer stage was basically for purposes of isolating the box or whatever from being interfered with by anything connected into its output socket, such as a lead containing a short circuit.

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jb38's 7,179 posts GB flag
Monday, 8 April 2013
Alan Watt
10:53 AM

Cannot make connection using HDMI cable to Humax PVR from Smartsung Smart TV, the tv is not connected to the internet.

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Alan Watt's 1 post GB flag

8:59 PM

Alan - it does not matter if the TV or the Humax is connected to the internet.

I suspect that as long as you put the HDMI from the Humax into an HDMI input on the TV and have the PVR switched on, you can select that input (the TV will automatcially select the internal tuner first) by using the 'source' button on the Samsung remote. Check the manual first, and then check the HDMI cable/inputs are working.

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MikeB's 2,579 posts GB flag
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