Freeview Signal Query...

Discussion in 'Freeview & YouView' started by Johndm, Jan 2, 2004.

  1. Johndm

    Johndm
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    How important is it to have the Freeview box FIRST in the RF chain?

    Just set up my new Pioneer box as follows:-

    New 10 element wideband aerial
    Old cabling used (thin brown)
    RF into DMRE60 first then FW box then TV

    Sandy Heath transmitter at 9 miles distance, aerial about 10 m high.

    Results

    ch 42,45, 43, 40, 46 all 73 to 90% signal at 100% quality

    ch 67 (MUX B) zero signal.

    Is it worth joining cable to reach FW box first, or just install another bigger aerial with better cable?

    regards
     
  2. LV426

    LV426
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    The important point to recognise here is that

    a) analog signals with some flaw, degrade 'gracefully'. In other words, you can often still see the channel in question, but it may suffer from some degradation - grain, shadowing (ghosting) etc.

    b) digital signals degrade disgracefully. Down to a point, you will see no effect on the picture; then suddenly (as the signal gets worse) you get either huge amounts of pixellation, blocking, freezing, break up or, indeed nothing.

    It is for this reason that wise counsel suggests giving the digibox the best possible chance of a clean signal - hence it should be first in the chain.

    A bigger, wideband aerial and a freshly installed cable (satellite cable with double screening is preferable) can and often do improve matters in marginal conditions.

    It is always possible that mux B (ch 67) is currently on reduced output for maintenance reasons. This happens more often than we realise. In the analog domain, the same thing may cause increased grain etc as above. In the digital domain this may drop the signal below the threshold needed for reception.
     
  3. Johndm

    Johndm
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    Thanks Nigel,

    Just checked transmitter info, and MUX's 1, 2, A, D, and C are from a 279m mast at 20kw ERP, but MUX B that I'm missing is from a lower 197m mast but still at 20kw.

    Will today just try putting box first in line, if no joy there, gonna wait until weather is better, then do cable and aerial.

    No too bothered, as I can get the missing channels via $ky.

    One other question, my present aerial is pointing towards a tree about 15m away, how much will the signal degrade when the leafs return in the spring?

    If Im gonna do the cable etc, maybe I need to get it higher.
    Its currently at gutter level (3 story building) but there's a nice chimney, although I ain't going up there without a parachute.

    regards
     
  4. Johndm

    Johndm
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    Just solved the problem, now have full 59 channels....

    It was so simple....my Panny DMRE60 DVD recorder was set to output RF channel 68, (although not even used), and it was interfering with the freeview signal, bearing in mind the recorder is first in the RF chain (due to short cable).

    Turned the E60 RF output to off, and got a signal on CH 67 straight away

    MUX B that I was missing is also transmitted from a lower height antenna than the other MUX's, so signal is slightly lower at 50% strength 100% quality

    Guess putting the FW box first would have acheived the same result (albeit with a join in the cable)?



    regards
     

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