Sudbury Transmitter - polar diagram of ch 68 signal strength

Discussion in 'Freeview & YouView' started by revd dave, Apr 20, 2007.

  1. revd dave

    revd dave
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    I am having difficulty with a wideband antenna receiving any signal strength from Sudbury on ch 68. I am Using an Alba freeview box which reports a moderate strength on ch 48, poor on ch 56, but none on 68. According to http://www.dtg.org.uk/retailer/tx_ea.html the power of the Sudbury transmitter(s) on each channel is 5.0 kW, 1.1 kW and 8.1 kW respectively. If ch 68 is so much stronger, even if my antenna has a bit of gain droop at the top end, why do I register absolutely nothing? Is there a strong directional component so that there is no signal here in CO4 0JX, Colchester North? Is there a web site which can provide polar diagrams of signal strength?
     
  2. SamRadford

    SamRadford
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    I suspect you are on the wrong track. You are in a tricky location with a weak digital signal and a strong analogue signal. If your aerial system has more than 6dB gain for any of the analogue channels, you'll end up "deafening" your Freeview tuner.

    In addition, the precise position of the aerial can be critical. Is it well above the roof and chimney? Too high or too low, too far to one side or the other, and results could be as you describe. What equipment did you use to position it? How did you check the compass alignment?
     
  3. revd dave

    revd dave
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    Thanks Sam.

    The current situation is that after borrowing a wideband antenna, aligning it with a friend using a hiking compass, we got fed up with finding no signal, so now I'm back with the old one, probably a band B.

    But if there is a strong analogue signal, it has to be on one of channels 35, 41, 44, 47 or 51. How am i going to be able to filter out those and get 68? Do I need a narrow-band aerial just for digital on 68? I also need to be able to receive digital on 39, 48, 49, 50 and 54. This is beginning to sound like an impossible job!

    It is also confusing: if, as you suggest, the box is being deafened to 68, why is it not also deafened to 39, 48, 49 which I receive perfectly? it does not make any sense.
     
  4. SamRadford

    SamRadford
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    Did you take note of my comment about "the precise position of the aerial can be critical"? The compass alignment is sometimes the least critical. The actual position of the pole and the height of the aerial can make a big difference. There's an example of that here:
    http://www.satcure.co.uk/reviews/review103.htm#02
     
  5. Phil S

    Phil S
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    I've never been able to get Channel 68 from Sudbury but get all others OK. I don't understand it either.

    However someone on a forum some time ago suggested that Channel 68 Sudbury is unidirectional North and Westwards and that's why they have the B transmiter on Channel 56 at a lot less power. Something to do with cross transmitter interference.

    Whether this is correct or not I have no idea but it sounds feasable.

    I scanned my freeview box to Channel 61 which is the equivalent Dover Mux. Works most of the time except in very hot weather. Get Meridian (Kent) local news instead but not bothered.

    Definitely something wierd with Sudbury 68.
     

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