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ERP reduced from transmitters after DSO

jasonjimbobjasonjimbob Posts: 1,374
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in Technical #1
I know that DSO was completed over 4 years ago, but I have always wondered why the transmitters had their ERP reduced, For example my local relay is Mynydd Machen, before DSO it transmitted the 4 channels with a ERP of 2.5 Kw, now it gives out 400 Watts instead, my guess is that now most relays transmit only 3 channels instead of 4 that the power levels didn't need to be too high?

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    chrisychrisy Posts: 9,419
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    #2
    IIRC it's a combination of how the ERP is quoted, and that the power levels don't need to be as high because a digital signal is more robust against interference.
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    Dr.OliverTwichDr.OliverTwich Posts: 1,582
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    #3
    Analogue erp was quoted as the peak erp of the vision carrier... power is not equal throughout the 8MHz frequency channel bandwidth.

    DTT erp is a mean of the whole 8MHz bandwidth.

    The lower DTT erp provides slightly better signal coverage to the area compared to the analogue power from the same site.
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    Nigel GoodwinNigel Goodwin Posts: 58,524
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    #4
    jasonjimbob wrote: »
    I know that DSO was completed over 4 years ago, but I have always wondered why the transmitters had their ERP reduced?

    They didn't - transmitter powers are the same in the vast majority of cases - your confusion arises because of the totally different method of measuring digital and analogue output powers.
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    Justin AerialJustin Aerial Posts: 5,710
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    edited 31/03/17 - 09:18 #5
    Nigel Goodwin wrote: »
    jasonjimbob wrote: »
    I know that DSO was completed over 4 years ago, but I have always wondered why the transmitters had their ERP reduced?

    They didn't - transmitter powers are the same in the vast majority of cases - your confusion arises because of the totally different method of measuring digital and analogue output powers.

    The advertised transmission powers in ERP are down, but because digital doesn`t need such a high power to (theoretically) achieve the same reception result they actually went up. This table of received signals before and after DSO show it well. Purple is excessive signal. Before DSO on analogue, only Enmley gave excessive signal at the test site. After DSO, on digital, Emley, Bilsdale, Belmont, Waltham and Crosspool all did, despite their quoted transmission power being reduced by a factor of 5.
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