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TETRA TV interference complaints

  • 10-04-2009 2:14pm
    #1
    Registered Users, Registered Users 2 Posts: 2,358 ✭✭✭


    Any of our posters from the north-east have more info on this story?

    Came across this:
    http://www.dundalkdemocrat.ie/dundalknews/New-Garda-mast-affecting-television.5150775.jp


    "
    New Garda mast affecting television reception in Dunleer

    Date: 08 April 2009
    By Tamara O'Connell
    ANGRY residents have lodged complaints with Dunleer Garda Station because a newly installed communications mast is interfering with their television reception.
    The mast was erected as part of a nationwide scheme to enable a new digital mobile radio service for use by the emergency services including An Garda Síochána.

    According to the Commission for Communications Regulation (Com Reg) the new service will allow communications within and between the emergency services to be more effective in areas which have poor reception.

    See this week's Dundalk Democrat for the full story


    "


Comments

  • Registered Users, Registered Users 2 Posts: 1,432 ✭✭✭pbirney


    ComReg have posted info here:

    http://www.askcomreg.ie/other/tetra_related_overload_of_television_masthead_amplifiers.327.LE.asp

    It seems that the onus is on the "end user" to ensure that filters are installed with masthead amps. to avoid such interference.


  • Registered Users, Registered Users 2 Posts: 820 ✭✭✭SRB


    It seems that the onus is on the "end user" to ensure that filters are installed with masthead amps. to avoid such interference.

    Yup, same in the UK, "been there done that" with OFCOM.


  • Registered Users, Registered Users 2 Posts: 967 ✭✭✭Rippy


    Tetra is starting to create problems here in Cork.
    System is similar to GSM cellular phone networks, but signal strength is much higher due to larger cells. Frequency is 393 MHZ here in Carrigaline and also Kinsale. Similar frequency used nationwide. Vertically polarized wideband aerials looking through the Tetra TX mast is the worst case scenerio.
    I measure 70 db @ 1 KM from mast in Carrigaline. This will overdrive many masthead amplifiers , creating problems at higher frequencies (eg UHF TV band)
    Some or all channels will be affected.
    Solution is to remove the amplifier if it is not raelly needed (many are not) .
    If it is needed a change to a variable gain amp with give out of band rejection normally does the trick.
    My current favourite is the Wolsey WFAV25.
    IN severe cases a Hi pass band filter installed before the amp should be used.
    In Kinsale the the problem was very severe and so many complaints were made , the Tetra TX was switched off.
    Theres no Tetra radios yet anyway!


  • Registered Users, Registered Users 2 Posts: 32,417 ✭✭✭✭watty


    DTT is also overloading mast amps as in many cases the Analogue signal power was far to low and the DTT is sensible power.


  • Closed Accounts Posts: 5,178 ✭✭✭STB


    TVi is nothing new. As far as I can remember, Back in the 90s NTL were fitting filters in areas to stop TVi (in main probably caused by kids with dirty txs). Bit strange the Tetra IF issue in Dundalk. Presumably mastheads at full whack pulling in Freeview from accross the border.

    As watty says turning down the power in the masthhead probably resolves these issues and DTT reception shouldnt need that much boosting


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  • Registered Users, Registered Users 2 Posts: 9,235 ✭✭✭lucernarian


    Dunleer is not Dundalk and virtually every TV installation would have a Group A masthead amp along with a group combiner (21-37/39-68 seems most common). By far the most common grp A amp would be the Fringe supreme masthead amp, with 30dB gain.

    A tetra mast nearby would hockey such an amp into overload. But good amps with low noise figures (the above seems to have only 1.9dB noise) are needed to pick up Divis in most areas south of the border.

    And the noise locals are kicking up over this will pale into comparison when RTÉ decide to broadcast 130W of DTT from the lourdes hospital in Drogheda on the same allocations as analogue Divis.


  • Registered Users, Registered Users 2 Posts: 2,399 ✭✭✭OFDM


    If you're going to use a wideband amplifier you MUST put a filter before it. Otherwise you're just leaving yourself open to problems. Most tv installers haven't even got third level qualifications so wouldn't have known to do this in the past. And if people just wanted Irish stations they wouldn't need amplifiers in the first place! :D


  • Registered Users, Registered Users 2 Posts: 32,417 ✭✭✭✭watty


    Not true. MANY populated areas need mast amps just for RTE. I'm only 13km from Woodcock Limerick and need it for analogue. Digital will likely work with a screwdriver as an aerial as it's a sensible power level.

    Many of the original sites chosen for roof top aerial Band I coverage with minimum number of sites and are poor for UHF.

    There are also many rubbish amps too.


  • Registered Users, Registered Users 2 Posts: 967 ✭✭✭Rippy


    OFDM wrote: »
    If you're going to use a wideband amplifier you MUST put a filter before it. Otherwise you're just leaving yourself open to problems. Most tv installers haven't even got third level qualifications so wouldn't have known to do this in the past. And if people just wanted Irish stations they wouldn't need amplifiers in the first place! :D

    Nonsense.
    In the context of TV masthead amplifiers 'wideband' refers to all of UHF band, 471 to 855 Mhz.
    Why MUST you put a filter in front of an amp to reject out of band reception?
    As Watty stated, most mastheads are rubbish and will amp a lot more than the UHF band.
    No experienced professional installer, regardless of his educational attainment, is going to use a filter on virtually every installation.
    He will use proper amplifiers with a low noise figure , good screening and good out-of band rejection, and use band-pass filters where necessary.
    Masthead amps are routinely needed to achieve a decent signal in MOST Irish homes away from immediate Metropolitan areas. Also a better way to amplify the signal for multi point distribution in the home than a distribution amplifier, which are either very expensive or completely crap.


  • Closed Accounts Posts: 5,178 ✭✭✭STB


    Most of these mathead amps are up full whack (for whatever reason) when installed. They need to be turned down by the installers.


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  • Moderators, Regional North West Moderators Posts: 19,158 Mod ✭✭✭✭byte
    byte


    On the topic of bad masthead amps, I've found Fringe Electronics to be one who offer amps that have little to no out-of-band rejection, including both wideband and grouped amps.


  • Closed Accounts Posts: 1,634 ✭✭✭Mayo Exile


    This isn't TETRA interference is it? (See picture)

    Its related to the thread I posted to the interference on my analogue UHF reception via a communal TV system. Grp A reception from Divis and grp C/D reception from Clermont Carn is affected. It seems to come and go without any regularity. Also DTT reception from Divis is wiped out altogether when this interference is occuring on analogue. If I didn't have the DTT engineering tests from CC I'd have no RTE/TV3 reception. Satellite reception also available via the shared TV system is not affected.

    Thread: http://www.boards.ie/vbulletin/showthread.php?t=2055506372&highlight=analogue+uhf


  • Closed Accounts Posts: 1 chieftain1


    i live in dundalk and have intermittant interferance. it is clearly down to tetra as when amp is removed and arial direct to tv irish stations are fine. does anyone know where to buy a decent filter or know of any makes i can get online


  • Registered Users, Registered Users 2 Posts: 32 B@ndit


    Tetra, dont think so, it looks like your TV is in a fish tank.


  • Closed Accounts Posts: 8,018 ✭✭✭Mike 1972


    Many of the original sites chosen for roof top aerial Band I coverage with minimum number of sites and are poor for UHF.

    Is that not a slight exaggeration given that only one of the original sites (and two relay sites) ever used Band 1.


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