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Freeview set-top aerials

Freesat Freeview euro tv skyThe best kit, The best programmes

2 What Satellite & Digital TV

Freeview set-top aerialsAs TV sets with only a digital terrestrial TV tuner become more popular and as analogue switch-off moves across the nation, the use of a simple set-top aerial for Freeview reception becomes critical

If you have any cravings for a half-decent TV picture (and as a reader of this magazine you

surely must) you would be foolish to rely on a set-top aerial for your main TV.

When it comes to other sets – in bedrooms, kitchens, and those temporarily used – you may not have access to a properly distributed signal from the main antenna. That’s when a set-top aerial is not the poor choice, but the only choice for Freeview reception.

What’s wrong with a set-top aerial?A set-top aerial works in the same

way as one in the loft or externally fitted

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– it has a conductor of the right size to actually pick up the signal and a number of guides and reflectors to enhance its sensitivity and/or directionality. The difference is that a set-top antenna is smaller and is usually inside the building.

As the signal spreads out from the transmitter, it is reduced in level. Any obstructions on the way to your home also reduce its level and the walls and windows of the building diminish the signal yet further, so an aerial inside is getting a much-weakened signal at the best of times.

Add in the low gain of the smaller antenna and you have a recipe for not

picking up enough signal to provide reliable Freeview reception.

Can a set-top aerial work for Freeview?

Set-top aerials can be used for Freeview if you are in a strong signal area. If the TV transmitter is nearby you’re getting a stronger signal and the reduction by the house walls won’t have such an effect on the signal level at your aerial.

You can get an idea of the likelihood of a set-top aerial working by consulting the Wolfbane DTT signal prediction website (www.wolfbane.com/cgi-bin/tvd.exe) and entering the postcode of your home.

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DigiTal recepTion

A simple Yagi aerial, although the lead may not reach a useful spot

The low gain of a set-top aerial and the reduction in signal strength by the home walls mean that while it may operate adequately near to the transmitter, far away it will not provide sufficient signal

An aerial with built-in amplifier, but it may just amplify the noise

Transmitter Near Home Far Home

Threshold Threshold

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What Satellite & Digital TV 3

ABC guide to... Discreet ‘flat’ aerials are popular but basic physics don’t bode well for the results you’ll get

Wolfbane displays the transmitters available and the expected signal levels at your home, along with a recommended aerial type.

If the recommended aerial is a set-top model then, of course, the chances of one working are good. You may also have some luck with a set-top aerial if the recommended type is a log periodic. It’s worth trying if the predicted field strength at your home is over 65dBµV/m, and you’ve got a very good chance of success if it’s over 75dBµV/m.

But bear in mind that if only some of the Freeview multiplexes reach your home at a sufficient strength for a set-top aerial, then it is only the channels on these multiplexes that you will be able to receive, and you will have to put up with an incomplete service, or fit a full-sized external aerial.

It’s also worth remembering that if switchover hasn’t yet reached your area the DTT signals are likely to be stronger when it does. You’re more likely to get Freeview (or all of Freeview) when the digital transmissions are switched to the more powerful transmitters after analogue has been switched off.

What sort of set-top aerial is best?Specifications given for set-top

aerials are frequently woefully vague or just downright misleading. Amplified aerials (with a built-in signal booster and powered from the mains) are often quoted as having a high gain – but only because of the booster; the aerial itself may be pathetically insensitive.

Size usually does matter for set-top aerials; the bigger, the better. However, the trend is for smaller, plain-looking aerials, so they are less obtrusive in the home. Go for a model that looks like, well, an aerial – a large, old-fashioned one.

If you can put up with it in the room, your best choice is probably a relatively small external aerial – just used indoors. Find out what works for near-neighbours

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glossary

AerialDevice to receive broadcast electromagnetic TV signals and convert them to electrical signals for processing by a receiver.

MultiplexTransmission at a single frequency containing a number of digitally encoded and compressed TV and/or radio channels. Freeview operates in six multiplexes (1 and 2 for the BBC and A-D for commercial broadcasters), each carrying up to about 12 full-time TV channels. One multiplex will be used for HD transmissions in the future.

Elegant Art Deco styling, but could reduce the potential gain

and follow suit. See if you can borrow one and try it at home – even if this is before your own personal switchover, a set-top aerial that performs well with analogue TV should be OK when you go digital.

Don’t spend a fortune on any model; it’s unlikely to serve any better than a cheap model. Many users have found the best option to be the cheapest set-top aerial they can find – even from a pound shop! Whatever the cost, before you buy it make sure you can return it for a full refund if it doesn’t work for you.

Will amplification help?Many of the more expensive set-top

aerials include a signal amplifier but this won’t necessarily improve your Freeview reception. The problem is that the amplifier can only boost what it receives and, for a set-top aerial in a low-signal area, what it receives is a small signal and a whole lot of noise.

Amplification is normally used to overcome losses over a long cable run to the TV or splitting the signal for multiple TVs. A set-top aerial feeds one TV, very close at hand. Sometimes, if the signal is ‘nearly there’ with the occasional drop out, then an amplified aerial can just tip the balance. However, it’s often the case that amplification in a set-top aerial is there only to disguise a very poor aerial.

How to set up a set-top aerialThe big disadvantage for set-top

aerials is that they are lower than external or even loft aerials, and the higher the aerial, the fewer obstructions to the transmitter and the farther from sources of interference on the street and in the home. Aligning a set-top aerial is fiddly and may need re-doing every so often.

The aerial needs to point at the best

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source of signal but because it’s inside, with lots of obstructions and reflections around, that may not mean pointing directly at the transmitter. Set-top aerials also don’t have to go on top of the TV.

You should experiment to find the best orientation and the optimum place for the aerial anywhere in the room within the constraints of the cable (on top of a nearby wardrobe often works!).

Most Freeview receivers and TVs include a screen that displays the signal strength and quality, and this should be used to position and align the aerial for the best reception.

Remember that you may need to position the aerial differently for the best reception from different channels, as they are coming from different transmitters. To make sure of all the multiplexes try reception of BBC One (mux1), ITV1 (mux2), CNN (muxA), BBC Four/CBeebies (muxB), Sky News (muxC), and Viva (muxD) n Geoff Bains