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What polarisation

Discussion in 'Satellite TV, Sky TV & FreeSat' started by chris, Feb 11, 2003.

  1. chris

    chris
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    Hi all.....

    I am thinking of getting myself, one of them freeview boxes....

    But according to the web sites......
    One i tried, said that i cannot receive freeview, where another suggested i can recieve around 90% of them.

    My local transmitter would be Dover (Kent) and when i put my mates post code in, it says that he can receive them.
    He is in folkestone, so seeing as i am on the Romney Marsh, which is very flat and from the sea front, just down the road, i can see the transmitter......i would have thought that with an aerial upgrade and a pre-amp...i might be able to recieve them....but to give me a better chance, i was just wondering what polarisation they are transmitting in (horizontial or vertical).

    Been looking around for an aerial, but all i can find at the mo is:

    Argos do a 52 element, or maplins do a 48 element......are there any bigger ones i can buy.......
    Are these channels transmitted on 400-500 Mhz...?...as i might be able to get a second hand 88 element Multi beam, that was used for the 70cm's ametuer (sure that is spelt wrong) band..that seems to cover 400-500 Mhz.

    Any help please....just want something new to play with, as Ham radio has become boring to me now.
     
  2. Chris Muriel

    Chris Muriel
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    Only channels 21-24 are below 500 MHz. I reckon the 70 cms amateur antenna will be way off optimum gain & match for the rest of the UHF channels.
    The Dover analogue channels are around 50-56 i.e. 700-750 MHz.
    This needs a group C, D or E aerial. Find out what channels are used and then get an antenna for the correct group. It may help if you find out what local neighbours are (successfully) using - or ask your local independent TV shop or aerial rigger.

    Chris Muriel, Manchester.
     
  3. gaz.thomas

    gaz.thomas
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    Televes make a 75 element wideband aerial that kicks out about 19dB of gain - couple this with a good quality masthead amplifier and you should be able to receive the dtt signal OK.
    The bbc has a spreadsheet on its site detailing the polarity and transmission frequencies of both analogue and digital transmitters.
    Try http://www.dtg.org.uk as a starting point for further info - I think their postcode database is the most up to date.
    After that i'd just make sure everything was suitable screened and you should be away.

    Gaz
    -x-
     
  4. Fernsehman

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    I was reading an eBook "Piping TV Around the House" ( http://www.The-Cool-Book-Shop.com ) and it says that the more elements you have, the more critical the alignment. In addition, the wind loading increases with the number of elements. This means that a high gain aerial can suffer badly when it's windy. So don't use any more elements than you have to.

    The polarisation depends on your local transmitter. They are all listed on the BBC web site. (There's a link to it in the book but it's on my other PC). You can get high gain aerials from satcure by mail-order next-day delivery.

    Fman
     
  5. pop-blue

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    I install a lot of freeview boxes in the Dover area. Are you off the Hoffam transmitter and do you get good reception?
    You should be tuned in as follows
    Bbc1 Ch 50
    Bbc2 CH56
    Itv1 Ch66
    Ch 4 Ch 53
    If you tuned into these and getting good reception then give it a go...
    There is a transmitter round hythe area and i don't think that's a digital transmitter
     
  6. chris

    chris
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    Thanks for all the replys........

    I did not know there was a transmitter in hythe!!

    That might mess my theory up a bit.

    I thought all my channels came from the dover transmitter...........

    BBC are ok......ITV is ok most of the time, depending on the weather.
    Channel 4 is ok and only get channel 5, via sky.

    Maybe i will pop round the local TV shop and see if he has sold any digi boxes, to locals......
    I was in dixons today, looking at the boxes....i was thinking of, either the nokia or hauppage box......but the ol sales assistant says, "dont waste your money on that crap"......"you want the grundig one, we never have any returns with them ones".

    He also adds " it depends weather you can get freeview as well"

    So he sticks my postcode into the freeview website checker.....and of course it comes up with cannot recieve them.
    He then tells me, i would be better off getting sky, which i already have.

    Anyway.....thanks for all the info and suggestions....i might do a bit more reserch first, before i spend around £200, just to recieve nothing......evern if i do get them, i am still only spending the money to get the local news, with a better pic....as sky show the news for Portsmouth and Brighton....not the local news for my area.
     

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