Mux 1 - Oxford - channel dropout

Discussion in 'Freeview & YouView' started by foraminafera, Apr 18, 2007.

  1. foraminafera

    foraminafera
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    I get dropout of BBC channels (Thame - postcode OX9 3XQ) from Oxford - and on checking the DTG website I see a common factor - they are all on MUX 1.

    I've just got a decent Freeview box (Humax 9200PVR) and can see my signal strength is 60% typical and on some channels occasionally 25% - TV OK otherwise except for THESE channels that just vanish. The other channels don't show any drop off I can see when this happens and they are all on Oxford.

    Suggestions / recommendations? I have priced up an Antiference aerial, masthead amp and new cabling (3 drop leads) and it's not cheap. Am I barking up the right tree here? (and no - I am not climbing up to fit an aerial -do not even THINK of suggesting it...).

    If anyone can recommend an installer and suggest a guide price?
    1 x aerial
    1 x masthead amp (if recommended)
    1 x chimney lashing kit
    3 x drop leads - 2 x upstairs and 1 x downstairs.

    Thanks

    JJ
     
  2. SamRadford

    SamRadford
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    Wolbane http://www.wolfbane.com/cgi-bin/tvd.exe?DX=L&HT=10&OS=OX9+3XQ suggests you install a log-periodic aerial. Useful info here:
    http://www.satcure.co.uk/tech/logperiodic.htm
    That page also mentions a suitable masthead amp. You'll need suitable (double-screened) cable.

    BUT!
    Your predicted signal is 57dBuV/m for digital. Add another 8dB from the aerial and you have 65dBuV which is fine.
    The problem is that the analogue signal is strong - 73dBuV/m and adding 8dB aerial gain to this takes it to 81dBuV, which is on the limit of what most Freeview boxes will tolerate. If you further amplify this, you'll have to add an attenuator to each Freeview box to prevent overload (until analogue is switched off).
    Analogue: http://www.wolfbane.com/cgi-bin/tva.exe?DX=L&HT=10&OS=OX9+3XQ

    In fact I would suggest that you don't need an amplifier if the aerial is above the roof. And if you want to run more than one Freeview box you can use a good quality passive splitter.

    You'll find everything you need on the Satcure site.
     
  3. ittim

    ittim
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    Im wondering if the problem you describe is the cause of my biggest headache.

    We have freeview at my work place (ox44 7pf) - i'm actually from Thame myself.
    We have an aerial on top of the roof and there are no other buildings around, however i can only pick up about 15 channels on freeview. ( i need bbc news 24 and can't get it)
     
  4. SamRadford

    SamRadford
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    ittim your analogue signal is too high. You may need an attenuator. If you wish to discuss it further, please start your own discussion. Don't hijack this one.
     
  5. ittim

    ittim
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    I wasn't aware i was hijacking it, thought it might be relevant since the op is litereally a couple of miles down the road.
     
  6. foraminafera

    foraminafera
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    Well - to clarify - it's not just that they are all on MUX 1 - it is all of MUX 1 I lose.

    The PVR signal strrength indicator gives me under 25 -> 75 % (depending) - is this consistent with too strong a signal? The current aerial is a standard analogue (no frills) chimney mount - and the same model as most of those around. I had the cable checked a year or so ago (water penetration) - standard co-ax. The other non-Mux 1 signals are all fine.....

    Had a cheap and cheerful ASDA Freeview box before - same problem (so it's not the receiver). Also had a Samsung slimfit Freeview TV - same problem as well (for a short while - returned/refunded - SD input upscaling from VCR/DVD was abysmal on a good day [aretfacts]).

    It's going to cost me a fair packet for a new antenna -I need to be fairly sure I make a right choice.
     
  7. SamRadford

    SamRadford
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    1. You can't rely on ordinary "low-loss aerial cable" to give good results for digital.

    2. You can't rely on the signal indicator of a Freeview box. A low reading could easily be caused by signal overload, causing the tuner to wind down its AGC (automatic gain control).

    3. Problems can be caused by something as simple as the wall socket, or the "fly lead" connected to it, or by signal reflections from a nearby chimney, aerial or other structure.

    4. Your standard analogue aerial is probably a Group C/D type, which is designed NOT to receive lower channels, so the BBC mux on UHF channel 34 may well be received very badly. I really think you should go for a log-periodic, as recommended. Be sure to get an installer who knows what he's doing.
     

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