Aerial attenuation. How much is too much?

Discussion in 'Freeview & YouView' started by Toto Man, Sep 15, 2007.

  1. Toto Man

    Toto Man
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    I ventured under the floorboards today to explore how the tvs are all wired up in the house. We have a rooftop aerial, fitted by a rigger 5 yrs ago, which comes into an attenuator labelled 0-20dB. I presume this gadget is reducing the signal strength by 20dB. From this, coax runs into a two way splitter or should i say combiner (the RF output from our Virgin Media box also feeds into this). The coax output then goes into an 8-way powered splitter which feeds all the TVs in the house. On most our TVs, especially the 14-incher in the kitchen, the signal looks fine. Channel 5 is a little poorer than the rest, but expectedly so. However on my 48-inch TV the picture is notably awful with lots of speckles. I actually get a better feed if I just connect an indoor aerial directly to my TV! I was therefore wondering what would happen if I removed the 0-20dB attenuator from the circuit? Is this a dangerous move? Am I likely to fry all TVs in the house by doing this? I just think 20dB is a hell of a lot of attenuation. In Scotland, digital switchover is thankfully not until 2010 so I'll be enjoying analogue TV for another 3 years. I was also therefore wondering, will digital TV require a stronger feed than analogue? If the answer to this is yes then removing this attenuator could prove to be vital. All opinions welcome :)
     
  2. sbowler

    sbowler
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    Shouldnt do any damage to the TVs, depends how close you are to the transmitter. I removed a 10db one from our ariel and there was no noticeable improvement or degredation of the signal. It could be that because it feeds into the spliter box and this amplifies the signal then the attenuater is needed. Removing it could make the picture worse, I would try it and see. Although you do so at your own risk and I am not a qualified ariel installer, try googleing the problem and see if anyone else has tried this. Digital TV or freeview did require my antenna to be slightly better aligned with the transmitter. You may need to upgrade the ariel anyway for future Freeview reception.
     
  3. SamRadford

    SamRadford
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    The label "0-20dB" suggests that it's adjustable up to 20dB.

    Digital transmissions will undergo changes at the time of switchover so it's difficult to predict what you'll need - especially since you don't say which transmitter.
     
  4. Mr_Fantastic

    Mr_Fantastic
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    Variable Attenuators are difficult to record the position so be very careful before altering it or you might need to call out an Aerial installer to redo the work which will cost you money. Removing it might be the best option. But before doing so, make careful notes on how it is connected so it can be re-installed if things are worse afterwards. I doubt whether you have any signal meter so it would be a trial and error exercise, seeing if it improved things. Checking again at different times of day and in different weather conditions.
     

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