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Possible easy way of improving DTV reception.

Discussion in 'Satellite TV, Sky TV & FreeSat' started by Mr.D, Feb 25, 2003.

  1. Mr.D

    Mr.D
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    I was playing about with my nokia Gondigital box the other day and discovered something interesting.

    I'm not a mad fan of having RF output stages that you can't switch off if required. In these circumstances I always try and select an output RF frequency that is as far away as possible from any broadcast frequencies. My digibox was tuned to 67 initially as I figured this was miles away from anything.

    The other night I changed the RF output frequency to a different one ( can't remember exactly what but I decided I could get it further away from any possible frequency conflicts with reference to the crystal palace main frequencies. ( it was changed to somewhere in the 30s but away from the main broadcast frequencies).

    After doing this I discovered I could no longer recieve ITV and Ch.4 !
    Changing the RF frequency back to 67 gave me a worse picture on the rf input on the TV but lo and behold ITV and Ch4 came back no problem.

    When I initially bought the box I found replacing the uplink coax lead to the TV with a slightly better brown coax job I knocked up myself practically eliminated any glitching or breakup I'd get when two stroke engines or old bangers drove past the house ( handy indication the pizza had arrived though!)

    So in conjunction with my dabblings the other night I'm now convinced the rf output stages on these things are at least partially responsible for interfering with initial reception in the first place.

    So if you are getting some nasty reception try shifting the RF output frequency and get a better uplink kead than the one that came with the box.
     
  2. Costas

    Costas
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    I tend to agree with your findings. My Nokia 221T was preset on channel 69 (!). I moved it to 28 and I lost Channel 5 and ITV was breaking up. I moved to 43 (which is very close to frequencies transmitted here in the West country) and .... bingo the signal has never been as strong before!! Consider that I leave in an area where the post code check will tell you that is is unlikley to be able to receive digital terrestrial...
     
  3. Fernsehman

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    This isn't exactly rocket science. I read this in "Piping TV Around the House" last year. It explains how to decide which channel(s) to use without simply guessing between 21 and 69. Guessing becomes a bit tedious if you want to pipe your VCR, Freeview and Sky Digibox outputs to every TV set!
     
  4. Mr.D

    Mr.D
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    My point is that the uplink to the TV should not interfere with the initial downlink reception to the digibox in the first place.

    The fact that it obviously does ( even when its a frequency well away from the regional ones) means there is a severe amount of RF leakage from these things and many people who have initial reception problems might well be advised to replace the lead that connects the digibox to the TV and change the output frequency.

    I suggest this is even preferable to having it disconnected and thats even preferable to using the lead that comes with these things which seems to act more like an antenna than a shielded cable.

    This is not about having some manky UHF video senders and VCRs outputting signals that don't interfere with each other its about the output stages on these boxes interfering with the reception stage.

    I'd certainly agree that some shabby 8quid pamphlet is not necessary to explain the "intriquacies" of moving a video signal about the house (for which solution I wouldn't touch an RF solution with a proverbial bargepole)
     
  5. jim.rae

    jim.rae
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    Yuo can find out all about co channel interference and which channels to avoid (both analogue and digital) at www.rcru.rl.ac.uk/tvrec/vcr.htm.

    You'll see it's a lot more complicated than you might think and guessing channels is really not an option...
     
  6. Costas

    Costas
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    Thank you jim.rae for the good information
     
  7. Mr.D

    Mr.D
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    Once again I'll restate my point. The RF output stage on a digibox should not be so leaky that it interferes with the digibox initial reception.

    When I modified the RF frequency in the first place I did it with reference to the local transmitter frequencies. All my other RF outputting devices in the house are disabled as the manufacturers are obviously a bit smarter than Nokia.

    I don't need RF and on the digiboxes I strongly suspect its responsible in some cases for poor reception .
     
  8. Costas

    Costas
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    I agree with you. I simply thanked jim.rae because the link he provided provides good info when you need to have RF.
     
  9. jim.rae

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    I agree with both of you!
     

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