A new aerial or an Attenuator ?

Discussion in 'Freeview & YouView' started by kcat, Sep 4, 2007.

  1. kcat

    kcat
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    Hi,
    We have a roof mounted group C/D contract aerial ( about 12 years old ) which feeds into a booster behind the main TV ( via Sky and a DVD player ) and then gets fed around the house. This works fine for analogue TV and Sky/DVD's. We pick up from the Oxford transmitter and I was told a very strong signal, the transmitter is about 12Km away and nearly line of sight from the aerial.
    We now have a freeview box which is having some problems picking up certain channels. Mux1 channels are fine even though they are broadcast outside the Group C/D (C34) but Mux2 stuff breaks up all the time. Some of MuxA channels are OK like Five US / Life but BidTV and Pricedrop have problems. The Freeview box only gives a Signal Level and this is around 85-90% for the Mux1 channels but 60-65% for the Mux2 stuff. BidTV on MuxA shows around 80% but still breaks up.
    Do I need a better aerial to increase the signal for Mux 2 /A or could our strong analogue signal be causing problems and should I try an attenuator - would a strong analogue signal also cause problems on the other Muxes or only on the weker ones ?.
    Any advice very welcome.
    Thanks.
     
  2. Chris Muriel

    Chris Muriel
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    An attenuator (in line with the Freeview feed) looks like a good option from the results you've outlined.
    The reason Mux1 works ok would be because that mux is outside the official bandwidth (frequency range) of the aerial and so there is less gain at the Mux 1 frequency - so you have "natural attenuation" by default.

    Chris Muriel, Manchester
     
  3. kcat

    kcat
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    But surely the analogue signal doesn't have 'natural attenuation' because of the aerial so Mux1 should be even worse ?.

    Opps, the analogue would be attenuated as well. silly me.
     
  4. kcat

    kcat
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    It must be a very fine line between working and not as Mux1 on C34 at 10,000w works great but I can't get anything on MuxD on C29 at 8,000w.
     
  5. SamRadford

    SamRadford
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    This is way too high. Although there's a lot of variation between Freeview box signal displays, you can pretty well bet that anything higher than 80% is going to cause problems. The reason is that the analogue signal is a lot stronger than the digital signal so if the digital is 80%, the analogue is likely to be 100% or more and will "blind" the tuner. I would recommend you try a good quality log-periodic aerial without an amplifier and check the signal. If it's still too high, fit an attenuator to the Freeview box aerial input. You really need to get it down to 60% or less.
     
  6. kcat

    kcat
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    I manually tuned Channel 29 and All the MuxD stations are being received fine now. Mux2 is the one with the big problems which is on Channel 68. Think I might just try an attenuator first before figuring out what to do about an aerial.
     

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