need a new aerial...

Discussion in 'Freeview & YouView' started by muttyhc, Sep 16, 2007.

  1. muttyhc

    muttyhc

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    so i bought a topfield 5800 a few months ago, but my aerial is really poor for freeview. I cannot get channel 3 and 4 during the day (signal strength is too low) and channel 5 is beginning to play up, but during the night I can get them OK.

    My nearest transmitter is Sandy Heath but the wolfbane site says its in group E which doesn't recieve all channels? The next closest is woltham which I think is a much lower signal from me. It says I need an amplified extra high gain aerial. (any suggestions are welcomed)

    I'm looking at maplins but is there a better place to buy one from? Also how hard are these things to fit? Thanks.
     
  2. Mr_Fantastic

    Mr_Fantastic
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    Digital Aerials are quite difficult to fit compared to Analogue. The equipment to make a reasonable job of it would cost you anything from £150 to £200 for a basic meter, thousands to do it properly with bitrate error information.

    I would not waste time at maplins if you are determined to do it yourself and don't mind wasting money if it doesn't go right. A very good Aerial can be purchased for around £40. A group E Aerial covers quite a wide range of channels and a Group E is what Wolfbane says you require, it also recommends that for me but I went for a Wideband Aerial, your Muxes should be in it's range. Wolfbane will show what channels the 6 muxes are on and What channels a Group E covers. Finding a Group E Aerial will not be as easy as finding a Wideband Aerial. A Wideband Aerial would do the trick. People recommend different Aerials and some have different strengths and weaknesses. Check out the CAI recommended ones. Televes makes some decent Aerials and the DAT 45 is fairly popular.

    http://www.dtg.org.uk/retailer/benchmarking.html

    The wolfbane site does tend to overestimate the required Aerial, an Aerial like it suggests is not usually necessary.

    Putting up an Aerial will mean climbing onto the Roof, finding a suitable place to fix it, somewhere where it is sheltered from Wind, roads and other sources of interference. Fixing to Chimneys can mean the Chimney falling down etc etc. If you put it up and find it is not good enough, you may need a mast head amplifier and adjusting that without a meter will give unpredictable results. It is just not as easy as Analogue TV where you can see the TV picture quality that is why it is really a job for an experienced Aerial installer who knows his stuff (many do not).

    Information on what you have already would help people judge what is needed. If your current Aerial is a set top Aerial then that would explain why you are having trouble.
     
  3. muttyhc

    muttyhc

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    that dat 45 looks like it would do the trick and is reasonably priced too.

    I guess I'll go with a wideband one. So this placement of the aerial wouldn't be neccersarely near the analogue aerial? Am I not able to put it up and if its bad change the location of it?

    I will have a look at my aerial, but as far as I can remember it is an old one which got improved about a year after channel 5 came out to be able to recieve that channel properly.
     
  4. Mr_Fantastic

    Mr_Fantastic
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    Is it external? It is not in the loft is it? How many elements does it have?

    Discount Aerials do low prices on Aerials, they are on eBay but all their stuff is buy it now. You do not bid against other people. They have a phone number which you can order from rather than on the internet if you want to. I have ordered a lot from them, they are okay but their advice (if you ask for it) is not all that accurate and some of it is wrong. But for prices, they are good.

    You could replace the Analogue Aerial, that might be the easiest place for it, especially if it has a Mast. But remember that the Dat range are very directional, they do need pointing in the correct direction. A meter is the only way to get it pointing in the precise direction for maximum signal strength and they cost about £150+. It is a bit of guess work without one but should be possible as I have pointed mine without a meter when I could not be bothered taking the Aerial cable back out of the loft to allow connection of the meter. The location it needs to be pointing can be worked out, it is given on the wolfbane site but that is not a compass direction, it is relative to ordnance survey grid north which changes each year. A conversion needs to be done to get the exact compass direction and you would need to see an ordnance survey map to get the required info to work that out. You could see an ordnance survey map at your local library. Then with a compass, line up a distance object to the correct compass direction and point the Aerial at it.

    Have a look around at the houses in your road, maybe ask who has had an aerial professionally fitted. Then you can use that as a guide to sitting it and pointing in the correct direction. Then just point it in the same direction as a professionally fitted Aerial within a few houses of yours.

    There is a book available "The Freeview Bible" on the satcure site on, they sell pdf's and has lots of info on Aerials and fitting them and setting up Freeview.

    http://www.satcure.co.uk/freeview_bible.htm

    If you go for the DAT 45, it might be worth getting the MRD and PSU with it and maybe a variable Attenuator, that will allow you to reduce the signal so that your freeview box does not become overloaded by Analogue signal until the Analogue gets switched off. The MRD is meant to reduce impulse noise which can cause picture problems from car ignitions, electric motors (lawn mowers etc) and it also amplifies the signal like a Mast Head amplifier does.
     
  5. SamRadford

    SamRadford
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    Sandy Heath requires a Group E aerial, although a wideband ought to work OK. Multiplexes use UHF channels 40(C), 42, 43, 45, 46(D), 67.

    However, if you are anywhere near Dallington park transmitter, it could easily swamp your Freeview signal and cause the problems you've reported. In this case it's unlikely you'll get much improvement before analogue is switched off.

    But we need to know your postcode.
     
  6. muttyhc

    muttyhc

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    i live in northampton. How much would it cost to get a professional to come and fit my aerial just out of interest? I will do the rounds phoning around but if any of you have a rough guesstimate it'd help.

    also my current aerial isnt in the loft, its external. Ill have to check on the elements.

    Thanks for the replies too they are very helpful.

    Saying about having to turn analogue off, well only my room has freeview, if it were changed to digital aerial only would the other rooms still be able to recieve channels 1-5 without a problem?

    here is what wolfbane actually says for me,

    [​IMG]

    Thanks.
     
  7. LV426

    LV426
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    Yes, a "digital" aerial (which is, simply, a regular UHF aerial of the right type for your location/transmitter) will pick up analogue as well.

    There is no such thing, really, as a "digital" aerial. They are all fundamentally the same. Digital TV comes in the same (in the broadest sense) frequency range (i.e. UHF ch 21..68) as analogue TV. Any UHF aerial is equally capable of picking up both; provided that it is sensitive enough and of the right grouping - and this is because digital signals are typically of lower power, and may be in a different spread of frequencies within the UHF band. This last bit is the only reason why we may need to improve our aerials.
     
  8. SamRadford

    SamRadford
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    I think you misunderstood my mention of the analogue switch-off date, which will occur for you in April 2011.

    What is Wolfbane's analogue prediction? You need both in order to decide what will work best.
     
  9. maldonian

    maldonian
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    Hi Nigel

    There is another reason, and it's important. An older (pre-digital) aerial is unlikely to have a balun. An aerial intended for digital reception should have some form of balun.

    Here's why:

    Impulse interference can affect digital reception much more than analogue. It's typically produced by starting or stopping an electric current - light switches, thermostats, motor brushes - especially if there's some associated arcing, and it's carried around the house by the house wiring. One way it can get into the TV is by pickup in the outer of the TV downlead. Without a balun the outer of the coax effectively becomes part of the aerial because the unbalanced coax is connected directly to the balanced dipole. A balun (a balanced to unbalanced transformer) stops pickup in the coax outer from being transferred to the coax inner at the aerial terminals.

    This didn't matter in the pre-digital days because impulse inteference just produces white dots on analogue pictures. But impulse interference can wipe out digital reception briefly (light switch) or continuously (electric motor).

    Good feeder pickup rejection is one of the requirements of the CAI/DTG aerial benchmarks. Without a balun, an aerial is unlikely to pass.

    If you look at the Blake website, they show which of their aerial ranges are suitable for digital reception (see here, column 4). The ones that are have baluns. If some aerials are suitable for digital reception and some are not, and in some areas a wider aerial group is needed than previously, then it's understandable that aerials are sometimes referred to as "digital" aerials. (On the other hand, it's quite possible that some cheap "digital" aerials don't have baluns and shouldn't be called digital.)


    Edit: changed DTG to CAI/DTG
     
  10. SeanT

    SeanT
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    Sandy Heath is your only realistic choice there, get a big old (new, digital!) aerial that gains up at the higher end and you should be sorted, only add a masthead amp if you aren't putting a distribution amp in the loft anyway.
     
  11. mrfreeview

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    Firstly the analogue signals from Sandy Heath are in the range of a Group "A" antenna.

    The DVB-T signals are NOT in Group "A" but are spread from channel 40 through to channel 67 meaning that an Antenna designated Group "E" is required.

    So to receive both Analogue and DVB-T from Sandy Heath a wideband antenna is actually required.

    You should also note that at some time in the future as part of the digital switchover a number of the MUXs (not all) from Sandy Heath are to be moved so that they are within Group A.

    Forget Maplins, they sell junk! You really need to look at professional apparatus. The Televes DAT45 is a very good choice of antenna for Wideband www.televes.com and is not that expensive. You would need to complement this is a good quality screened Coaxial cable - Copper foil around the dielectic is the best.

    The DAT range of antenna from Televes allow the dipole to be replaced with what is termed a "margin raising device" basically an amplifier right behind the dipole.

    However for receving Sandy Heath DVB-T there are other "Tricks" that you can deploy that would allow you to apply much large amounts of amplification to the DVB-T signals without having problems of amplifier overload caused by the higher level of Analogue signals being present.

    I have a DAT 45 and then apply 24dB of amplification to my DVB-T from Sandy Heath, after removal of the analogue signals. PM me if you want to know more about how you can do this.

    I hope my post has been of use
    :)
     
  12. SeanT

    SeanT
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    Surely this is just a bandpass amp like the ones on satcure and not a top secret pm me device?
     
  13. mrfreeview

    mrfreeview
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    Nothing "TOP Secret here"!

    I offered the PM so that I didn't have to write anymore that perhaps nobody was intrested in take the option on...I think I had written enough!

    Which amplifer product sold by SATCURE are you refering? Any chance of posting a link?
     
  14. SeanT

    SeanT
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    I don't know, I've seen them, will take a look when I have a minute :)
     
  15. simon123

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    i am a CAI member and for a standard wideband rig charge £150 inc vat for the complete job. If you are looking at a large aerial eg dat 45 with mrd this will need to go on heavy duty mast and brackets and the price could rise to about £275.

    hope this gives you an idea.
     
  16. mrfreeview

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    If you feel competent to climb a ladder up to the side of your house then you can easily install by yourself.

    I fitted a Televes DAT45 without the MRD, just the standand dipole, onto a suitable mast secured to the side of the house with "Horse Shoe Brackets" (but you can use T&K) and all in all the price of the materials was <£100
     

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