Type of external TV aerial for ground floor extension

Discussion in 'Audio Visual' started by Oddbod1, 11 Aug 2017.

  1. Oddbod1

    Oddbod1

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  3. Lucid

    Lucid

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    I wouldn't touch the second aerial with a barge pole. Go for a Log Periodic.

    Is there a specific reason why you've zeroed-in on the very short Log P aerial?
     
  4. Oddbod1

    Oddbod1

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    It's the first one that came up on amazon prime.

    Also we had our main 40 year old aerial on the chimney replaced about two years ago and was told by the installer we didn't need the spider x type aerials because we might get ghosting I think. We are in a good signal aerial and there wasn't a need for the other type pen longer log p type. 8 spokes or whatever's it's called was enough.
     
    Last edited: 14 Aug 2017
  5. Astra99

    Astra99

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    The main problem is that amazon neither know nor care what aerial group you require. That is why, for these suppliers, the favourite is always the wideband. If you are served by the Durris transmitter, (if the information from a Google search is still current), you will need a Group A aerial, as most of the channels you receive are in the 20s. My advice? Go to a local aerial installer and buy the aerial from him.
     
  6. Lucid

    Lucid

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    You asked "How does one decide?". There isn't a simple answer to that, especially for a novice making their own choice.

    Those of us in the trade who want to do it right spend time studying and use our field experience to validate what we learned. That helps build up some local knowledge of what aerials will and won't work in certain areas, and it also helps to sort the wheat from the chaff with all the aerial choices.

    The crunch point for me came after a couple of years running my own home cinema & audio visual installation business. Aerial installs was something I normally handed off to local installers, but often I'd find that corners were being cut that either affected the quality of my customer's signal or that made my job harder. That was when I decided enough was enough. I did some training, lots of reading, bought some proper test gear and really got to understand what the differences are between a good and a poor installation.

    That SLX aerial claims to be a 36 element rig. That's BS. They're counting the cross elements as 4 each when they're really just two at most, and counting other bits as multiples too. It's more like a 13 element aerial, but 36 looks a better number when someone who doesn't know any different is leafing through a catalogue. From experience I can see that the general construction of the elements uses thin bits of aluminium bent in to shapes that attempt to give then some strength. But you've only got to look at a few of your neighbours houses to see similar aerials where the fins have been bent by birds and then the aerial gets mangled by the weather.

    The next place people get ripped off is with cable. Good coax isn't expensive - we're talking a few tens of pence per metre, - so the cheap stuff isn't really that much cheaper yet it loses a load more signal, and does a crap job of keeping out interference, and the outer jacket weathers far quicker so it ends up causing a load of hassle with lost signal or letting water in to the back of electronics so you have to spend on the decent stuff and just hope that your telly or PVR isn't corroded to hell. That kit includes 10m of cable, and it's likely to be the cheap stuff. The difference in price netts out at a saving of £2-£3, that's all.

    Your recent aerial install on the roof is a short Log Periodic. Mounting up high makes a big difference to the amount of signal that an aerial will generate. The same aerial mounted just 3m from ground level might generate as little as 20% of the signal strength just from being closer to ground level. Power in itself isn't so important as quality. Background interference is always present; so if the aerial is generating less signal then the margin between the signal and the background noise will be reduced too. You can't regain that with amplification because the amp boosts the noise too and adds its own. This makes the signal to noise ration worse, not better. A larger aerial (a bigger Log Periodic aerial) can help redress the issue. If you have space to fit a full sized Log Periodic then do it.
     
  7. winston1

    winston1

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    The cross elements are one. The reflector is one. I make it a seven element aerial.
     
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  9. winston1

    winston1

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    The installer was lying. There is no ghosting with digital. However he was right to suggest a log periodic type.
     
  10. Oddbod1

    Oddbod1

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    Its quite possible I misquoted him. But he did say that I didnt need the other aerials that others houses had especially since the signal was now digital and didn't need to pick up the analogue signal.
     
  11. Lucid

    Lucid

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    There's a grain of truth somewhere is what you say he said; digital has its own problems, but happily, ghosting isn't one of them.

    The signal for digital TV works on a lot lower power than analogue TV did. This means the signal reaches further, or if your house is close to a transmitter then you won't need a large aerial to get decent reception. That being said, even in the strongest signal areas I still wouldn't install a compact Log (or any compact aerial) on the roof any multi-story home.

    While a high-mounted small Log would be perfectly fine feeding a single TV, there may come a time when the house owner wishes to distribute the signal to feed several TVs. If there's enough signal from the aerial then that could be done with a simple (and cheap!) passive splitter. The alternative is a powered splitter, but that introduces a bit of its own noise in to the signal chain. The point is that either solution relies on there being a healthy margin between the background noise (interference) and the signal level being generated as the aerial receives the transmissions. The smaller the aerial then the smaller too that margin.

    A full-sized Log wouldn't have been much different in price. I can tell you that from my national wholesaler that the difference is less than £2.00 at trade for the larger aerial. That translates to maybe a fiver to the end customer. Given the inaccessibility of a roof aerial then it's not an easy thing for the average house owner to change once they realise the implications of what's installed. This then either limits the scope of any future expansion or makes that expansion more costly than it would have been but for the sake of £5 during the first installation.

    For a ground floor install I would only choose a compact aerial (Log or otherwise) if the installer could show me his aerial meter displaying no less than 60 dBuV signal level from the weakest mux. If he couldn't, then I'd insist on a full sized Log.
     
  12. bernardgreen

    bernardgreen

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    Are you saying that with digital transmissions there are no multi-path problems ?
     
  13. winston1

    winston1

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    I disagree with that. It is measured in a different way that gives a smaller figure. Average carrier power as against peak vision carrier power.
     
  14. winston1

    winston1

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    No. We are saying there is no ghosting. With digital multipath signals add together to reinforce. Obviously there is a limit when it just drops out, but that limit is way beyond when multipath on analogue would be unusable.
     
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