interference between sky and terrestrial

Discussion in 'Sky Digital TV Forum' started by Eager Beaver, Mar 7, 2006.

  1. Eager Beaver

    Eager Beaver
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    I am getting interference between sky and terrestrial.
    Everything from sky comes out on rf2 and is fed into global distribution box in loft.Picture on the main tv is perfect as it comes via scart but on the other tv's the picture has lines in the backgound that move from left to right.
    If i remove the terrestrial aerial the sky picture is great and if i remove the connection from rf2 and join it to the incomming aerial thus bypassing the sky box then the picture is again great. How can i make both work together without losing picture quality ?

    Hope someone can help

    Eager Beaver
     
  2. JayCee

    JayCee
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    It sounds as though the Sky RF modulator is clashing with or too near another channel and needing adjusted.
    Press "Services", 4, 0, 1, "Select", "RF Outlets", "RF Channel no" and change to something else at least 3 channels apart from any of the analogue channels..."Save new settings" and "Backup" 3 times to exit. The default RF Chan is CH68...you will need to retune every TV fed from the distribution amp to the new RF channel.
    A bit of trial and error should see you sorted.
     
  3. Eager Beaver

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    Cheers for info but how do i know what other channels are set to?

    Eager Beaver
     
  4. JayCee

    JayCee
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    Just find out which transmitter serves your area and have a look at http://www.dtg.org.uk/retailer/transmitters.html and you can find the channels for each station.
     
  5. Heinz

    Heinz
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    Set the digibox to any UHF channels except the 5 used for analogue TV in your area, the 6 used for DTT multiplexes in your area, the channel you use for your VCR, +/- 1, +/- 5 and +/- 9 channels from any of those.
     
  6. Eager Beaver

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    Tried several different numbers and even removed scart cable and video connection and the picture is still the same.Any more ideas?

    Eager Beaver
     
  7. JayCee

    JayCee
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    What make/model no is the Sky digibox?
     
  8. Eager Beaver

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    It is a AMSTRAD DRX200

    Eager Beaver
     
  9. JayCee

    JayCee
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    Just as a quick test...do you get the same interference if you take the output to the distribution amp from RF1?
     
  10. Nick_UK

    Nick_UK
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    The terrestrial signal could be too strong - it might be causing intermodulation interference inside the distribution amp. Try an attenuator in the aerial cable to the box - you can get these from Maplin - part number BW59P for a 6dB attenuator, or W60Q for 12dB (both £4.99 each). Try the 6dB first.
     
  11. Eager Beaver

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    Still have the same problem

    Eager Beaver
     
  12. Heinz

    Heinz
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    Please list in your reply to this post the channel numbers of the 5 analogue channels in use in your area, the 6 channel numbers used for DTT (Freeview) in your area, the channel your VCR modulates on and the channel your digibox currently modulates on.

    Analogue BBC1 -
    Analogue BBC2 -
    Analogue ITV1 -
    Analogue Channel 4 -
    Analogue five -

    DTT Mux 1 -
    DTT Mux 2 -
    DTT Mux A -
    DTT Mux B -
    DTT Mux C -
    DTT Mux D -

    VCR -

    Sky digibox -

    I will then reply with a choice of channels to which you should change the digibox's output.
     
  13. Eager Beaver

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    Filled in all details but dont know how to tell what channel vcr is on.

    Eager Beaver
     
  14. Heinz

    Heinz
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    Knowing what UHF channel your VCR modulates on is vital to the whole setup but, if it is not considered, the following should be suitable for use as the RF output from the Sky digibox:

    21, 22, 23, 24, 25, 26, 27, 29, 30, 33, 62, 63, 64, 65, 66, 67 & 68 (I ignore 69 because it is not reserved as a TV channel in the UK and may be subject to broadcast interference).

    Personally, I'd set the VCR to 22 and the Sky digibox to 67 (I avoid 'bookend' channels so as to minimise possible breakthrough from adjacent PMR etc. services).
     
  15. Eager Beaver

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    Tried all channels suggested and still have same problem

    Eager Beaver
     
  16. Heinz

    Heinz
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    That suggests that the UHF channel on which your VCR is modulating is the problem so you need to find out how to change that.

    To check, take the VCR out of the RF loop completely (connect the incoming terrestrial aerial to the Sky digibox's RF in socket and from the digibox's RF1 socket to the TV only). The problem should then not be present.
     
  17. Eager Beaver

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    Still got same problem but i need to use rf2 to distribute picture and change channel in other rooms don't i ?

    Eager Beaver
     
  18. JayCee

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    Yes, but he only suggested this as an experiment to eliminate the VCR as the source of the interference.

    Did you try an attenuator?
     
  19. Eager Beaver

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    i had already removed the video from the equation when i did a similar test after your previous suggestions on the rf1 channel.

    I have tried a 16db attenuator cos i had one and if i put it before the sky box then the picture was crap but if i put it after the sky box on the rf2 then the picture was good but the sky link stopped working.
    Not had chance to get a 6db or 12db attenuator as suggested by NICK UK earlier in this thread.
    Would i not have been better using a poor quality aerial i wonder ?

    Eager Beaver
     
  20. Nick_UK

    Nick_UK
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    An attenuator could cause the Sky link to stop working. It would seem that your existing aerial has too high a gain for the signals in your area.
     
  21. Eager Beaver

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    How can i tell what gain i have and if i have the right aerial?

    Eager Beaver
     

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