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Curious signal problem since London DSO

Discussion in 'Freeview' started by Chris Green, Apr 18, 2012.

  1. Chris Green

    Chris Green Member

    I've got 3 devices daisy-chained to my aerial pointing roughly south east towards CP from west London.

    The first, my Humax Fox-HDR T2 and the second, my Sony hard-disk recorder have re-tuned just fine (and yes, I did remember to back up the timers thanks to the custom software in the Hummy!).

    Oddly, the third and last device, my Panasonic 37" plasma set now gives me a slight problem that I never had before. Despite what appears to be both a 100% signal and 100% quality when viewing the Panny's tuning menu, I seem prone to picture break up when watching BBC1 (SD) and associated channels. For the first time ever, this set has also detected stray channels on this multiplex in the 800 range.

    Could it be that the Panasonic has the most sensitive tuner of the three items?

    I've seen somewhere that an over-strong signal can represent itself like a weak one, giving similar picture break-up.

    Does it sound like I need an attenuator fitted to this last stage of the aerial cable?
  2. gomezz

    gomezz Well-Known Member

    Are you sure it is not the channels in the 800 range which are the ones intended for you rather than the BBC1 etc channels in the normal range? If so you need to delete all the channels on the TV and do a manual scan of just those MUXes you need from your local preferred tranmitter.
  3. Scuttlebroom

    Scuttlebroom Member

    Hi Chris, if you look at ukfree.tv, they mention that if you get 100% signal, this is too much as you should get around 75% for it to be OK. Look at this page:


    Also it mentions that you need to do a complete first time install, I set my panny DVD Freeview recorder to shipping condition then did a first time set up, I don't get any channels in the 800 range and my signal strength is around 80% and I am in SW12, might be the problem you have?
  4. gomezz

    gomezz Well-Known Member

    Thanks for that reminder as there was a Power Up event on the Oxford transmitter overnight to go along with full DSO at Crystal Palace. I checked my signal strengths and they were all banging on 100% so removed one of my daisy-chained room end boosters and got the strength down to 70/80% across the MUXes with 99/100% quality reported.
  5. Chris Green

    Chris Green Member

    I wouldn't have thought so - the unwanted channels in the 800 range are all on channel 23 along with the correct ones, so even if I did a manual tune picking the multiplexes one at a time, I'd still capture them. They also have very low signal strength and 'iffy' quality %ages. I can only imagine that maybe the Panny's tuner is too sensitive for its own good and I'm also picking some other distant transmitter's channel 23 content too.
  6. Chris Green

    Chris Green Member

    It just got curiouser and curiouser. Realising that the channels in the 800 series appeared to be those that should on the channel 22 multiplex, not 23 where they kept showing up, I checked and found that 22 hadn't been tuned at all, and on attempting a manual tune of that frequency, my set's meters showed an appaling signal. This could also be the answer to a few of those "Where's Dave Gone?" queries.

    However, remembering what's been said about over-strong signals presenting as if they are poor signals, I tried a 6db attenuator which OnDigitial reckoned I needed in the first place all those years ago, and bingo. One retune later, I've got all the channels - still showing 100% 0f everything, strength and quality but now all fine. It would appear that channel 22 was perceived as being so strong that it couldn't be tuned properly and in some way was breaking through onto 23.

    Strangely enough, the Humax Fox- HDR T2, the first in line of the daisy chain is showing the ideals of 75% strength and 100% quality. I guess it's what I thought - the Panny tuner is too sensitive for its own good!

    As the 6db attenuator doesn't seem to be enough, I've ordered a variable 0-20db job off e-bay to see if I can get the strength down to the recommended 75%.
    Scuttlebroom likes this.