Strange DAB reception problem

Discussion in 'Hi-Fi Stereo Systems & Separates' started by Steveo82, Jan 3, 2018.

  1. Steveo82

    Steveo82
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    Strange DAB reception problem

    Hi there, first time posting so apologies if I've picked the wrong forum.

    I have a (admittedly quite old now) Cambridge Audio DAB 500 receiver. It has always been very reliable, but I am now getting a strange problem with reception that I don't really understand and think might be a fault that has developed after getting it out of storage and setting it up in my new place (which is a street away from my old place where it worked perfectly).

    The receiver picks up loads of stations when you auto tune (typically around 100), when you tune into pretty much any station and press the tune button to see the signal strength bargraph, it consistently shows a very high signal (usually right to the right hand side far past the minimum acceptable marker) however again consistently with every station if you then check the signal error rate it is always very high - typically around 70. Therefore all stations are completely garbled and inaudible due to this signal error (either silence or it just constantly pops). I don't understand how I can have such good signal strength and such bad signal quality across all stations? Wondered if this could point to a problem with the receiver?

    I've tried a number of different aerials (currently a DAB external aerial that is brand new with brand new cabling) and get the same problem with each I have tried? Also I have another cheap DAB kitchen radio (little thing) and that works perfectly in the same position with just a basic attached internal telescopic aerial. Any thoughts? It's got me a bit stumped? I figure it's probably just it's end of life but can't bring myself to chuck it out just yet!

    Many thanks in advance guys.
     
  2. JBA6

    JBA6
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    Steve, I know you say you've already tried different aerials but in case you haven't tried this one, it's cheap and works very well for me sited on our living room bay windowsill with both Arcam and Pioneer DAB tuners - the Vivanco TVA 200 which is just £7.95 in John Lewis.
    I was also amazed to find it worked very well with our Freeview TV which is normally fed by a proper loft mounted aerial.
    --
    JB
     
  3. HeadBanger

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    Does it pick up stations without an aerial plugged in? If so it’s possible that the DAB signal is too strong where you are now and it’s overloading the radio.

    An attenuator would fix it if you still needed to use an aerial.

    HB
     
  4. Steveo82

    Steveo82
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    Thanks for the responses guys.

    JB - for that price it is definitely worth a shot - cheers for the recommendation.

    HB - just tried it now and no stations are found with no aerial connected (also the scan completes very quickly). Guess that rules out overloading? Don't know anything about attenuators but I will look into this. Many thanks.
     
  5. Steveo82

    Steveo82
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    Hey HeadBanger - is this the sort of thing you were thinking might help me?https://www.amazon.co.uk/dp/B002KD7OPE/ref=cm_sw_r_cp_apa_2U.tAbJ1N2GEB

    Guess it's a bit odd that I didn't have these problems in my last place round the corner, but for a little over a fiver definitely worth a shot! Cheers
     
  6. HeadBanger

    HeadBanger
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    Yes, something like that although the non-variable types are generally better and don’t degrade the signal quality. Do check that the one you get attenuates the DAB broadcast frequency range.

    However, I don’t think that this is your issue. If you did have a really strong signal it would have picked up something without an aerial.

    Do you have somewhere else you could test it first, work or a friend’s house? If not I guess for £6 it’s worth a punt.

    Good luck!

    HB
     
  7. Steveo82

    Steveo82
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    The Attenuator didn't have the desired effect I'm afraid but was worth a punt as you say. I could see it doing it's job lowering the signal strength, unfortunately this just didn't make any difference to the signal error rate which stayed constant throughout.

    I’m going to try the unit out somewhere else nearer a transmitter, but am now fairly convinced it's just knackered - probably beyond economic repair given it's age.

    Unless anyone has any final thoughts think I'm going shopping for a new one. Although at least I will have a choice of four aerials now to use with my new unit :)
     
  8. Chris Muriel

    Chris Muriel
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    Try a complete reset of the receiver (if it has that facility in its menus).
    Also try a scan with no aerial connected followed by leaving it disconnected from the mains overnight.
     
  9. dannnielll

    dannnielll
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    At the frequencies that dab use, multi path interference from metal hoardings, metal on polyurethane foam wall insulation etc can cause interference, and the type of error rates you are experience.. good strength but unusable. So it could be fine in one room but hopeless in another. Sort of like the ghoasting we used to get on old analogue TV.
    The only solution will be a directional antenna preferably mounted in an attic, above, any metal foil., Pointed at your transmitter. You might need the attenuation in the downlead as directional Ariel's are high gain and signal power is not your problem.
     
  10. Steveo82

    Steveo82
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    Thanks for the suggestion Dan. I've already fitted an external dab aerial recently - admittedly not yet roof mounted, but even positioned far away from the house in a fairly open spot it didn't make any real difference (spent ages trying lots of different positions and orientations). Also another radio (a cheap little thing with a telescopic aerial) works perfectly in the same position as the problem unit which I would have thought would rule out interference from the house in that particular position?

    I contacted the manufacturer (Cambridge Audio) and they said the symptoms described suggest a hardware problem, after I went through the whole leaving it disconnected from the mains for 24 hours. Given it's age I think I plan on buying a replacement rather than spending anymore money on it. It would be £40 for the reseller (Richer Sounds) just to look at it and then cautioned they might not be able to fix it anyway due to discontinued parts (it is probably about ten years old thinking about it).

    At least I now have a collection of about 4 different aerials including the external one - surely my new unit will work with one of them (fingers crossed) :)

    Thanks for all your help/suggestions guys
     

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