Digital TV with Analogue Antenna

Discussion in 'Freeview & YouView' started by Tatious, Jun 16, 2009.

  1. Tatious

    Tatious
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    Ok, this might sound like a really stupid question, but my current home has had a digital antenna installed since I started using Freeview, so it has never cropped up...

    I'm about to move in to student accomodation (in the next few months) in the UK, and the house I am moving in to has an analogue aerial... What issues will this create in terms of being able to use the freeview that is built in to my tv?

    Also, someone might be able to help me, theres a consideration fo going with SKY, am I correct in thinking I can get a completely separate second box? One that allows me to watch what I want without controlling both boxes? If so does anyone know how much this costs? Is it a one off fee or an additional monthly cost?

    Thanks
     
  2. hornydragon

    hornydragon
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    Depends on the aerial some older ones are fine for freeview some arent...

    Sky multiroom is an extra box which costs £9.75 ontop on main box a month and you get the same channels as main box package totally sperate control
     
  3. grahamlthompson

    grahamlthompson
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    There's no such thing as an analogue or digital aerial. UHF TV aerials are just that designed to recieive a range of frequencies in the UHF band. Whether the UHF carrier has one analogue station or a multiplex of digital channels is irrelevant, the aerial simply receives the signal and passes it on to a tuner which extracts the video and audio. Pre DSO DTT at the moment though is very low power and may need a better aerial to get better reception. The same better aerial will improve both analogue and digital reception.

    Read this

    Trading Standards warns of digital switchover aerial rip-off - 16 Oct 2008 - Computeractive
     
  4. Tatious

    Tatious
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    Oh thats good then, so all I would need to worry about is aerial quality and signal strength?? And I presume if it is good enough I could get a signal booster to help?
     
  5. maldonian

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    Hi Graham

    Like it or not, the term 'digital aerial' exists and is here to stay, for a while at least. Go into almost any store that sells TV aerials and there they are, digital aerials - wideband aerials in boxes labelled digital aerials. Likewise, set top aerials are often sold as digital set top aerials. And most aerial installers advertise that they install digital aerials.

    Just think of the term 'digital aerial' as being short for 'aerial that is suitable for digital reception'.

    There is a good technical reason for distinguishing between current aerials that are definitely suitable for digital reception, such as the CAI approved types, and a significant proportion of older (pre-digital) aerials that are not as suitable because they do not have baluns.

    Digital TV is much more susceptible to impulse interference than analogue TV. Impulse interference just produces white spots on an analogue picture but it wipes out digital reception until the interference stops. Many old aerials do not have baluns, and without a balun the outer of the coax feeder is effectively part of the aerial. Any impulse interference picked up on the coax outer from nearby mains wiring will be coupled to the coax inner if the unbalanced coax is connected directly to the balanced aerial. Adding a balun at the aerial connection blocks this path and stops the feeder pickup getting onto the signal. (Feeder pickup in a receiving aerial is the converse of radiation from the feeder when an unbalanced feeder is used to connect a transmitter to a balanced aerial without a balun. Amateur radio enthusiasts will be well aware of this.)

    Feeder pickup rejection is included in the DTG/CAI benchmark tests for aerials. The benchmarking guidelines state that it is unlikely that an aerial without a balun will pass.

    Some older aerials have baluns, some don't. If you're in a strong signal area this probably won't matter because the received signal will be stronger than all but the strongest interference. But if you are in an area with medium to weak digital signal strength and you are using an old 'analogue' aerial for digital reception, it would be worth checking if it has a balun, especially if you suffer from occasional picture break-up or freezing. Or you could just replace it with a new CAI approved aerial anyway - and replace the old cable while you're at it.

    It's not that simple. Digital reception is affected differently by reception conditions, and in particular by impulse interference. A short burst of impulse interference that causes a barely perceptible effect on an analogue picture can wipe out a digital picture until the start of the next GOP (Group Of Pictures). As explained above, the aerial design can affect how much impulse interference is picked up.

    I think it misses the point about feeder pickup rejection. Many old aerials (and cable) are much older than the 3 years quoted by the TS people posing as consumers. I should think most 3 year old outdoor aerials have baluns. The CAI aerial banchmarking scheme was launched 6 years ago.

    Quote from the CAI about their aerial benchmarking scheme:

    The basis of the scheme is to lay down minimum standards for the technical performance of UHF TV aerials based on the specific requirements for satisfactory DTT reception.

    Says it all really.

    Try it and see what you get.

    Many factors will influence how well it works, not least being whether the aerial group is suitable and whether the transmitter it's pointing at is a relay (many relays don't transmit Freeview).

    A booster can help if reception is marginal. A low noise masthead amplifier close to the aerial would be best.
     
  6. Geofbob

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    Thanks maldonian for the technical information. But surely the point grahamlthompson was making when he said There's no such thing as an analogue or digital aerial was about older installed aerials, not those on sale in shops. And you're more or less endorsing his point when you say to the OP Try it and see what you get.

    The fact is that many people out there think that they will definitely need a new aerial when analogue is switched off; and the aerial maufacturing/retailing/installing industry is not doing much to dispel that fallacy - for fairly obvious reasons!
     
    Last edited: Jun 17, 2009
  7. shoestring25

    shoestring25
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    my parents just got a new LCD with free view and had an old analogue aireal they get alot of Free view channel's fine but no ITV or CH4 so I'm thinking you might not get these either without a digital aireal
     
  8. grahamlthompson

    grahamlthompson
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    You are missing the point every single point you make about the performance of a so called digital aerial will improve the quality of an analogue signal, sometimes to the point where the picture quality exceeds that of a digital signal. Once a digital signal reaches the point where there is sufficient margin to the digital cliff improving the signal has no effect on picture quality. Analogue on the other hand continues to improve so that with the best signals it delivers better pictures. If you have an aerial that delivers really good analogue signals now and fails to give reasonable digital signals there is a massive chance that after dso power increases it will deliver a good digital picture. Trading Standards are now warning traders about this misleading adverising and I know of at least one case where they have threatened prosecution. All the types of aerial you describe were available long before digital TV was even thought off. My first yagi array, a wideband had a balun years before digital terrestrial TV became a reality

    At least one professional organisation agrees

    PARAS - Professional Aerial Riggers Against The Sharks

    PS At least one manafacturer is now attempting to improve on this myth, there range of aerials is now described as HD ready.
     
    Last edited: Jun 17, 2009
  9. kit1cat

    kit1cat
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    They could need a wideband aerial to pick up all the channels, nothing to do with aerial type. I had the same problem.
     
  10. grahamlthompson

    grahamlthompson
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    If the OP posts which transmitter they are using it's easy to check what type of aerial they need.

    If they also put in their post code here

    UK digital TV reception predictor

    and report what the aerial recommendation is that will help.
     
  11. maldonian

    maldonian
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    The term 'digital aerial' is relatively recent and it's usually only used to refer to new or recently installed aerials. I'm not sure when it was coined, but I suspect it was a consequence of the DTG/CAI aerial benchmarking scheme that was introduced specifically for aerials intended for digital reception about 6 years ago. Manufacturers started indicating which of their aerials were suitable for analogue TV (legacy models without baluns) and which were suitable for both analogue and digital TV (benchmarked aerials with baluns). It's only a short step to go from 'suitable for digital TV' to just a 'digital aerial'. 'Digital' is commonly used to mean 'digital TV' in other equipment (digital tuner, digital set top box).

    I understand the point, but it's also a fallacy that old aerials are just as suitable as a new aerial. Some may be, but there are several reasons why some may not be - damage, deterioration, wrong group, relay transmitter, and of course the missing balun issue. Also it is quite likely that the old cable could do with replacing. Some aerials have been up there for decades, not just a few years. Aerial installers that know their area will probably be able to judge from an address what sort of installation they are likely to find there and what is needed for digital reception. But they should still make a site inspection before definitely saying what, if anything, is needed.

    No, you're missing the point IMHO. In fact you don't seem to have understood what I said. I only mentioned one aspect of performance, feeder pickup rejection, and it has no significant bearing on the quality of an analogue signal.

    Perhaps I didn't make myself clear enough. Analogue reception is not the issue. Aerials without baluns are not as suitable for digital reception as aerials with baluns. You can receive Freeview using an old aerial that hasn't got a balun, but it will be more susceptible to impulsive interference than using a similar aerial with a balun. This will remain an issue after DSO because there will still be fringe areas with weak reception.

    You only need a tiny margin to be clear of random noise, and in the absence of interference the picture will then be as good as it can be. But you need a much larger margin to be unaffected by impulse interference. This second margin is vague, there's no cliff edge. The stronger the interfering signal, the stronger the signal has to be to be unaffected by it.

    You may not be able to tell whether impulse interference is likely to be a problem just by looking at the picture for a limited time because impulse interference doesn't happen all the time. Typical sources are light switches, thermostats and badly suppressed mains-powered electric motors (electric drills, food mixers, shredders, etc).

    After DSO the service areas will be larger, creating new fringe areas outside the current service areas. Meanwhile some people in current fringe aereas may not want to what till DSO.

    As I said, some old aerials have baluns, some don't. Ideally some form of balun should be used whenever a balanced aerial is connected to an unbalanced feeder. But in the days of analogue-only TV, baluns were left out of some aerials to keep costs low.

    To sum up:

    - An aerial with a balun is equally suitable for analogue and digital reception.

    - An aerial without a balun is not as suitable for digital reception as an otherwise equivalent aerial with a balun, because of the feeder pickup issue, which affects digital reception much more than analogue reception. How suitable or unsuitable it is will depend on the signal strength: the stronger the signal, the less it will be affected by interference picked up on the feeder.

    - All benchmarked aerials have baluns. Some old aerials do not have baluns.
     
  12. LV426

    LV426
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    Thank you (both) for enlightening us at length about the nuances of what is, or isn't a "digital aerial". I don't see any value in further comment, either way, on this issue. Therefore, please refrain from further debate. Thanks.
     

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