back to article 4G interference will knock out Freeview

760,000 households risk losing Freeview when 4G telephony comes online, and even with mitigating techniques Ofcom reckons 30,000 households face a future without terrestrial broadcasting. The regulator reckons those 30,000 will have to switch to satellite or cable to get their TV broadcasts, as 4G telephony leaks into their …

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  1. Anonymous Coward
    Anonymous Coward

    Or....

    Build into the figures the cost of abandoning CH60 (i.e. paying for it carry no signals at all) and move everything on CH60 to other channels. If DTTV is so much more efficient then why can't CH60 simply be used as a signal air gap?

    1. Anonymous Coward
      Unhappy

      Re: abandoning CH60

      If you "abandon CH60", you can't just "move everything on CH60 to other channels". You have to accept that some people will lose some digital TV channels. There are various ways you can shuffle it around, to change which channels get lost and who loses them. But some people will be unhappy.

      Or we upgrade to better compression standards (MPEG4 and/or DVB-T2) and everyone with a non-HD Freeview box or TV suddenly needs to upgrade. That will make a lot of people very unhappy.

      "If DTTV is so much more efficient then why can't CH60 simply be used as a signal air gap"

      Well, DTTV is much more efficient, that's why CH61 and up were freed up. And it's why you get more than 5 channels on FreeView. And yet FreeView has comparable coverage to the old analogue service.

      If you really want a "signal air gap" without messing up FreeView, you can use CH61 for that. However, it seems that the mobile operators want to buy CH61 even if they have to pay to fix the interference - they obviously think it's a good deal.

  2. It wasnt me
    Thumb Down

    Or maybe.........

    .....the money grabbing pointless shites at Ofcom could not be so fucking greedy and put a guard band between the two different spectrum users. Like every one else has to. The problem is arising because spectrum has been sold which isnt technically available. They acknowledge that there is not a square roll of at the top of an allocated frequency, yet they have sold thte next available hertz anyway. Ofcom (or whoever licences the spectrum these days) should pay for the mitigating equipment, not one of the frequency users, who have after all licensed their respective frequencies in good faith.

    Money grabbing cocks.

    1. Anonymous Coward
      FAIL

      Totally agreed

      OfCom aren't doing their jobs correctly if two legally operating services on different bands are interfering with each other. When you pay for a block of frequency, you should be able to use that block of frequency- especially if it's going to be deployed across the country!

    2. Anonymous Coward
      FAIL

      Re: Ofcom should pay

      The 4G operators haven't licensed the frequencies yet. So Ofcom haven't "sold the next available hertz", but they're about to. And the buyer is not "licens[ing] their frequencies in good faith" expecting it to be interference-free; they will be buying it knowing about the interference. If the cost of fixing the interference is more than the spectrum's worth, they can choose not to buy it.

      The money's going to come from the 4G phone operator who gets channel 61. You're suggesting the 4G operator pays more and some of that money is used (by Ofcom) to fix the interference. Ofcom is suggesting the 4G operator pays less but have to fix the interference themselves. Either way, it costs the 4G operator the same amount of money, the same amount of money is used to fix the interference, and the same amount of money goes to taxpayers.

  3. Anonymous Coward
    Devil

    Another example...

    of why Ofcom is not fit-for-purpose!

    When will the coalition government wake up and get rid of this last bastion of NuLabour arrogance?

  4. Trollslayer Silver badge

    It's not difficult

    It is known as ACLR (Adjacent Channel Leakage Ratio) so just have a gap, say 2MHz and that will solve the problem.

    Even 1MHz would probably be more than enough.

  5. Anonymous Coward
    Thumb Down

    >"a £10 filter, which focuses the frequency received more accurately,"

    "focuses the frequency", does it? I don't suppose it also reverses the polarity of the neutron flow?

    That's a really mangled description of what a filter actually does. "Focus" != "restrict", and "frequency" very much != "bandwidth".

    This is supposed to be a technically-aware readership, you don't have supply Janet-and-John-level oversimplifications for us.

  6. Zimmer
    Flame

    Winter Hill?

    Perhaps this just affects us on the edge of the Winter Hill range. I believe the transmissions from there span Ch 54-62

    Anyone know the details for the transmitters in the South of England (eg London). I do not expect them to be affected :(

    1. Test Man
      Go

      Yep

      Yep, we'll be alright down here, as the range for both analogue and digital from the Crystal Palace transmitter is between 21 and 37 (Group A in other words), I believe.

    2. SImon Hobson Silver badge

      RE: Winter Hill

      Glad you brought that up. It talks about Ch 60 being at the top of the DTT band, while we go all the way up to 62 - heck, that's way better than going all the way to 11 instead of 10 !

      I think the bit about having a directional aerial is a red herring - I'm 40 miles from Winter Hill, so what's the chances of a base station ending up somewhere along that line of sight ? So there I am, with my high gain directional aerial - pointed right at a mobile base station.

      I look forward to hearing how they will deal with people who lose Freeview but aren't in a cabled area (which if most of the UK), and for various reasons cannot have a satellite dish.

      ANd as pointed out, if the regulator is basically saying "this will cause interference to other lawful users of spectrum, but we are still going to actively promote it and not just permit it" then that is one heck of a failure on their part to do their job !

    3. mittfh
      Holmes

      But surely...

      ...if there was no-one to regulate who can use which frequencies, it would be even more of a free-for-all than Ofcom's allowing at the moment. Ofcom are also who you complain to if you are offended by any programming content - although their rulings are little more than a slap on the wrist, if it was up to the broadcasters themselves, complaints would probably be filed in /dev/null. Oh, but according to Wiki, apparently the BBC has now been made responsible for dealing with interference to TV / radio signals...

      IMHO ideally, regulatory bodies should be non-profits completely independent of both the body they're regulating and the government. However, that does raise the tricky issue of how they should be financed...

    4. Mike Dimmick

      Retune coming

      Winter Hill does currently use C61 and C62 but these will be cleared in a later retune. Granada switched over when the plan was to release only C63 to C68, the Europe-wide agreement to clear C61 and C62 as well happened after the Granada switchover.

      The date of that retune has not yet been set. They're trying to integrate the necessary changes into the regions yet to switch over to minimize the overall number of retunes required, although largely only the changes to the relay transmitters, rather than the main transmitters, have been achieved.

      Your aerial will still have been designed to pick up signals in *at least* the C50 to C68 range, possibly C21 to C68 if you had a wideband aerial installed (though this was never necessary for Winter Hill). The additional signals picked up from the 4G phone transmissions are liable to overdrive the tuner in the set-top box and/or any boosters you might have - the key is the sum of all signals picked up by the aerial, not just the strength of the one frequency you're trying to decode.

      The following main transmitters in the Meridian and London regions also require Group C/D (C50 to C68), Group E (C35 to C68) or wideband before switchover:

      Hemel Hempstead (V)

      Reigate (V)

      Bluebell Hill (Medway towns)

      Dover

      Hannington (Reading/Basingstoke/Newbury)

      Hastings (V)

      Heathfield (East Sussex)

      Midhurst (West Sussex)

      Salisbury (V)

      Tunbridge Wells (V)

      Whitehawk Hill (Brighton) (V)

      Transmitters with a (V) transmit with vertical polarization.

      Many viewers outside these areas have fitted, or have had fitted, a wideband aerial. This is either because they were misinformed, were hedging their bets, or simply that the shop or fitter only stocked widebands.

      If Ofcom also flog off C31 to C38, as currently proposed (as '400MHz') people with widebands will also need a filter in the middle of the band.

    5. Anonymous Coward
      Anonymous Coward

      They are

      it's going to the EU.

      Then the gov will be told what to do...

  7. Adrian Challinor
    FAIL

    What a stupid idea

    We get everyone to switch over from analogue to digital TV (DTT). They get to change their sets or buy a freeview box. Once you get there, you find that the signal is corrupted because some mobile phone operator wants to sell the FanBoi's a report how many other FanBoi's are within shouting distance so that they can call them.

    Fantastic. Nice one, Ofcom. Just what is your purpose, because supporting customers sure ain't part of the job remit.

    So, what happens when I refuse to pay my TV license because I am no longer getting the serivice I used to get? Can we tell the TV Licensing authority to kindly ask Ofcom to hand it over?

    Or what happens when I complain that my signal has degraded? No-one can prove whether it has or it hasn't. But if I press my case, will the FanBoi mobile operator poney up for a new receiver or even a FreeSat dish?

    1. MrT

      In other interference cases...

      ... the operator of the source of interference has already paid for Freesat etc. Were I currently live, four wind turbines are roughly in line from most houses to the TV antenna about 2 miles away. Depending on the wind direction, and therefore the angle of rotation of the turbines, the TV signal breaks up even on the five main channels - some times Freeview loses ITV, Ch4 and Ch5, plus a bunch of the higher frequency ones, stuff like Dave, BBC4, 5*, some of the '+1' channels - can go from 60-odd channels to 29 on the programme guide. The RF generated by the turbines in enough to mess up terrestrial TV, so the operator in that case (IIRC it's EDF) sent a Freesat box to anyone who is affected. The deal stopped last year, but it gave existing residents back their TV service.

      Substitue the 4G operator in place of EDF and the result is the same - operator must pay for the remedy, and it's not always going to be a £10 filter.

    2. John Murgatroyd

      Well...

      given that the major land channels all have videostreaming of past programming....just watch it via iplayer etc....you do not need a tv licence if it is not live...

      1. Graham Dawson

        Or...

        just don't watch broadcast television at all. It's all shite anyway.

  8. Anonymous Coward
    Facepalm

    Great....

    So I can download angry birds in 10secs rather than 30secs, but I can't watch tv...Sound like a win to me!

    Seriously if someone can give me the address of the person responsible for this monumental cock up I have a clue stick here that has had way to much sunshine already.

  9. Eponymous Cowherd
    Devil

    DVB efficiency

    ***"DTT (Digital Terrestrial Transmission) is much more efficient, so can broadcast more channels in less space."***

    More like "DTT permits channels to be compressed to a barely acceptable quality, so can broadcast more channels in less space."

    As far as reception is concerned, it looks like I'm going to be completely fucked. Currently live right below the hill on which a major TV transmitter is perched. Can't get a thing from it, so I have to point my aerial at the next nearest, which is some 40 miles distant.

    A fuck-off big roof mounted aerial, mast-head amp and distribution amp give barely acceptable Freeview reception which drops out in poor weather and breaks up when any nearby mobile phone polls its base station.

    I *had* hoped, that come the analogue switch-off, the associated DVB power boost would improve things, but, given that its going to be almost certain that a 4G mast will spring up line-of-sight between me and the transmitter it looks like its likely I'm going to have to bin my Freeview kit and buy Freesat.

    1. Anonymous Coward
      Happy

      freesat?

      but... but... but ... there's no Dave on Freesat!

      /gibber

    2. John Murgatroyd

      get freesat

      the boxes are quite cheap and a sky dish and lnb work quite well....25 quid the lot..

      1. Gareth Gouldstone
        Stop

        I don't want a nasty satellite dish on my house ...

        already got a digital-capable aerial, thanks!

  10. Tegne
    Thumb Up

    Simple solution: Put SKY1* on channel 60 and everyone is happy.

    *Insert alternative channel peddling reruns & drivel.

    1. Lamont Cranston

      Reruns & drivel?

      That's pretty much everything, isn't it?

  11. Paul Shirley

    takes hard work to screw up this badly

    Bugger. After switchover I'll be using C29,54-59 and 61. So that's 7 multiplexes fucked in 1 go. Since the stupid sods packed 3 of them into adjacent channels last month I've had crap reception, now they'll throw in interference as well? Idiots.

    Also a little surprised, my transmitter is switching to use C61 in a couple of months. So assuming OFCOM aren't totally delusional there's going to be yet another channel shuffle after switchover, so none of us can even guess whether we'll be hit in 2013! OFCOM need a long time in the naughty corner.

    Still, I look forward to seeing just how much expense I can run up with whoever ends up liable for fixing my reception. With 2 PVR's, 8 Freeview tuners in use (and some spares), mast head distribution amp and they'll need to install a new rooftop aerial, it ain't going to be cheap.

    1. Mike Dimmick

      Waltham

      I'm guessing you're using the Waltham transmitter (it's pretty distinctive with just one mux out-of-group). The new frequencies for Mux 2 and A are not adjacent to any other transmissions from Waltham, so it's most likely that your boxes are picking up some services from Waltham and some from somewhere else. This happens if your box just stores the first version that it finds, rather than the best version. Check for any additional versions of the services in the programme guide, usually at around 800. If they're better, delete all channels and do a manual tune using the following frequencies: 29, 31, 33, 42, 45, 49.

      I'm using Crystal Palace, which currently has five out of six multiplexes adjacent to an analogue channel, and the other one is adjacent to one of those five. The HD mux (which I don't use, too far away) is between an analogue channel and another multiplex. There is no actual problem with being immediately adjacent if the levels are correct.

      You may find that with the increased levels now transmitted from Nottingham, that the combined level is either too much for your masthead amp to handle, or for the amplified output too much for the tuners to handle. When this occurs, the distortion adds weaker frequency-shifted copies of the signals (intermodulation products), which cause errors depending on how strong the signal is and how far the channels are apart - the closer they are, the more damage is done. Enough damage, and the redundancy in the transmission is all used up and the decoder can no longer recover the signal. Analogue signals were deliberately spaced three or four channels apart to reduce the damage this does, which appears as 'herringbone' patterns on the picture.

      Nothing will launch on C55 and C59 at switchover. They are tentative future assignments for local services.

      I'm hoping that Ofcom, the broadcasters and the transmitter operator Arqiva will pull their fingers out and sort out the final location for the BBC A multiplex before switchover actually happens at Waltham, but I wouldn't count on it. The current plan took about five years to develop to this stage. Ofcom basically seem to be letting the broadcasters figure it out, the data at www.digitaluk.co.uk is always more up-to-date than Ofcom's.

  12. Sartori

    Something I won't be worrying about

    Considering I can't get Freeview at all where I live anyway! Wrong side of a hill which nicely blocks out Winter Hill, which is a bit of a bugger

    1. Kevin Johnston

      Terminology

      "-which is a bit of a bugger-"

      I believe the correct phrase (by kind permission of HRH Sir Terry Pratchett esq) is 'a bit of an embuggerance'

  13. Peter Gathercole Silver badge
    Flame

    Eh?

    "But that 790MHz band butts right up against the top DTT band, known as Channel 60*"

    I know there is an asterisk against this (but I can't find the note that should go with it), but channel 60 is *not* the top TV band. TV bands go from channel 21 to channel 68, and on the Mendip transmitter, we currently have C61, C62 and C67 carrying terrestrial digital television. If we loose all channels above 60, we will loose all BBC channels, and many of the extra ITV and Channel 4 channels.

    Pointing the aerial the other way will give me Welsh television from Wenvoe. I don't understand Welsh (living in England) so this is no help to me for the channels I might loose.

    Also, I currently have a TV in several rooms in the house. I only have Sky on one of these. Are they going to pay for additional satellite boxes, together with a multi-channel LNB and all of the wiring in the house to maintain my current TV service?

    Also what do they mean by "and 5.7 million users who've plugged them into their own televisions"? Do they think that anybody who has *not* paid for a TV installer to plug it in are incompetent? I think the Electronics part of my degree probably means I understand more about transmission lines, aerials and the like than a TV installer who has probably done a one day course in how to read a compass and point the aerial in the correct direction!

    Admittedly, to do the job properly now there is no analog TV signal, you really need a signal strength meter to get the best signal, but there are ways and means if you don't have one.

    1. Peter Gathercole Silver badge

      Ahhh

      Answered my own question. On 28th September this year, users of Mendip have to re-tune our boxes again(!), presumably to have the channels shuffled down to lower frequencies. Can't find the exact details, but www.digitaluk.co.uk says that this needs to be done.

      1. Mike Dimmick

        Might be another subsequent retune

        http://www.digitaluk.co.uk/postcodechecker/main/traderegion/west shows the details of what's happening when. However, the BBC multiplex is still shown as C61 after the 28th, so there will have to be another retune to move this to somewhere else.

        You may still have to retune again next year, depending on how your box handles a mode change on an existing frequency.

    2. Anonymous Coward
      Trollface

      ...installers...

      ...don't use compasses, they point the aerial in the same direction as everyone else's...

  14. Anonymous Coward
    Anonymous Coward

    Big Business and Government

    'nuff Said! LOL!

  15. Giles Jones Gold badge

    Squarial

    Way to go Ofcom.

    Why don't they just kill DTT and use satellites anyway? The government in the 80s tried to create competition to Sky with BSB. Something similar is needed now that transplants Freeview to satellite without involving Sky.

    1. Mike Dimmick

      Freesat available, but ridiculously expensive to transition everyone

      Freesat already exists. All the traditional Public Service Broadcasting channels - that account for the majority of viewing - are broadcast free-to-air, do not require Sky equipment and do not require a decryption card. Freesat provides a free-to-air electronic programme guide on top of that, so that viewers only have to enter their postcode into the receiver rather than having to manually tune in every channel that is broadcast.

      There is a comparison of what's on Freesat vs what's on Freeview or Sky's 'free' service at http://www.ukfree.tv/compare11.php

      I reckon a lot of people are unnecessarily subscribing to Sky when they mostly watch stuff that is free-to-air.

      However, you are not going to get support for replacing every single TV installation in the country, particularly not second TVs in kids' rooms - certainly not straight after the transition to DTT.

  16. Robert E A Harvey
    Headmaster

    Oh?

    "£10 filter, which focuses the frequency received more accurately"

    Look, we are techies here. We know what bandpass and bandstop filters do. Not only don't you have to spoon feed us, I'd rather you didn't spoon feed us meaningless pap.

    "focuses the frequency" indeed. Been writing Dr Who scripts have we?

  17. Anonymous Coward
    Happy

    "replacing every single TV installation in the country"

    Maybe that would be too expensive (though it'd be a lot cheaper and better value for money than bailing out the banks or Greece and Ireland's bondholders) so here's a slightly cheaper idea (maybe).

    Offer the tiny percentage of the audience that regularly watches the +1 channels a bargain basement user-friendly PVR limited to +1 functionality. Close the shopping channels down and send anyone who cares the content on a weekly DVD (with a free DVD player if required; just imagine having your own in-home JML thingamajig).

    Maybe then there'd be enough bandwidth freed up to do something useful with.

    Ideally they'd use some of it for a different kind of programming in addition to what's already on offer, something actually watchable, but I'm not holding my

    breath.

  18. Herby Silver badge

    At one time...

    We had WIRED telephones, and WIRELESS television. Now we have WIRELESS telephones and WIRED (cable, etc) TELEVISION. Of course, one can also have point to point television using all the bandwidth to cover everyone's "instant gratification", instead of a broadcast medium, but that might be wasteful (so we should promote it for income streams).

    It is all silly. Most of the 4G crud is "broadcast" or streaming video anyway (big data hogs), and should be done as group addresses, but that would be too efficient. So everyone is happy that they can start THEIR TV program on a wireless connection at 7:03 PM, instead of 7:00 like everyone else.

    Do we need to be THAT connected?

  19. David 45

    Ofcom offal

    Sounds typical OFCOM these days. See the rumpus over power line internet distribution and the interference caused by same which they appear to be ignoring. Are they, or are they not, a regulatory authority? So..... REGULATE, like what you're supposed to, for goodness' sake!

    1. Anonymous Coward
      Anonymous Coward

      Their sole functions are

      Getting the cash in, denying any problems are their fault, and warming their arses ready for their impending move to either the EU or Big Biz

  20. Pyers

    Communal antennas

    Why is it stated that it is more complicated and expensive to fit filters to communal systems (CATV)? The filter goes between the antenna and input to any communal system (which normally consists of an amplifier driving a splitter where the amplifier gain should match the loss of the subsequent splitters). The level coming from the antenna in a CATV system will be similar to a home antenna so places no different needs of the filter whatsoever. If anything it will be cheaper as only one filter would be needed for each entire CATV system.

    Filtering is another question too, the top DVBT channel 60 ends at 790MHz and 4G will start within 1MHz or so above that. Filtering a signal as close as 10MHz let alone 1MHz next at a high frequency (it's the ratio of wanted/unwanted frequencies that is relevant) requires filters with a very high 'Q factor' (http://en.wikipedia.org/wiki/Q_factor) and multiple poles (stages) of filtering. In practise it means a relatively large physical size and silver plated cavity resonators, so it will be very expensive to implement . It will also have an increasing loss as the cutoff frequency is approached so will reduce signals in CH60 (and maybe lower).

  21. Anonymous Coward
    Happy

    "Do we need to be THAT connected?"

    No we don't (though some sheeple think they want to be), but where's the marketing opportunity in the old way?

  22. Anonymous Coward
    Anonymous Coward

    WInter Hill Panic

    This article started my alarm bells ringing as I am in The Winter Hill area. However, I have just found out, from one source, that

    "Channels 61 and 62 are to be withdrawn during 2013. Multiplexes using them are likely to be moved to 49 and 50 and those on 49 and 50 are likely to be moved to 39 and 40."

    Phew! So just another retune then. Panic over (I hope)

  23. Mike 137
    Stop

    The shape of things...

    "as radio transmissions are curved (not square)" - could a radio engineer explain this please?

    1. Richard 12 Silver badge
      Boffin

      It's a really, really, really bad way of saying that you can't have a 'perfect' filter*.

      So any RF transmission that is nominally at 400 MHz and 10MHz wide, actually does transmit power at 380MHz and 420MHz.

      How much depends on how good your filtering is.

      *Theoretically you could have a perfect filter, but it would take the signal an infinite length of time to traverse and require an infinite number of components. Apparently that's not desirable.

  24. BSmith

    Ofcom are not fit for purpose

    Stop being greedy!

    Get the phone operators to reuse some of their 2G or 3G bandwidth to offer 4G.

    From the digital switch over site "2013 final" shows that mendip will have the BBC A MUX on 61, right in mobile phone land and since there is a nice big phone transmitter on the hill, then I guess that will wipe out anything in coverage range of that hill.

    Brilliantly thought out guys, how much have you trousered to allow this to happen?

    Isn't part of your mandate to prevent frequencies being unusable due to this sort of thing?

    I personally don't see the need for 4G, but even if you do, it's still a bit of a joke to allow something everyone uses to be battered by an incremental step in something few have a real need for (if you accept that 2G and 3.5G do fine for phone and data on the move).

    Time to write to my MP about OFCOM being incompetent:

    http://www.writetothem.com/

  25. Anonymous Coward
    WTF?

    YES or NO: Ofcom couldnae organise a piss-up in a brewery

    Ofcom not fit for purpose - their brief, such as it is, has conflicts of interest that only seem to get resolved in favour of maximising income and disregarding basic technical issues like interference assessment and resolution. They cannot even keep to the Law of the land (e.g. EMC regulations)

    Oh wait - maybe they're not aware of basic technical issues given the drastic depletion of technically competent staff as retaining then would likely have cost 'too much money' and maybe they also consider themselves exempt from constraints of statute that allow them to operate in the first place.

    Well maybe it takes a pirate to catch a pirate

  26. Flossie
    FAIL

    No Satelite or Cable

    I can't get Cable (I tried, they won't extend the network by the 20 feet necessary to cover the last two buildings on my road) and the satellite signal is blocked by surrounding tall trees (again I tried), so DTT is all I can get. However, the signal is weak, I find a booster to be essential even though I have my own external ariel. This needs to be blocked,Offcom shouldn't allow new services which have the potential to degrade existing ones.

  27. Robert Forsyth

    Simple solution

    Just (re)broadcast the affected channels on 4G and give those affected a 4G set-top-box,

    oh wait...

  28. Graham Anderson
    Mushroom

    not another Granadaland retune??

    Granadaland has already had two DTT retunes. The first one I was able to talk my 80-year old parents through on the phone. The second screwed things up royally and my mother was left with the Welsh channels in one part of the house - the bit she actually uses. The house is big, so calling out an aerial engineer is a complete pain and an unwanted expense. My poor old Mum had to wait for me to come visit (from That London) and even as a reasonably techie person, looking up the correct channel groupings for Granada TV as opposed to Welsh was annoying and confusing. Add into this the Chinglish inspired set-top box UI for manually changing the channels and it was a nightmare. As it turned out, there was a problem with the box as well, but the process was so confusing that I didn't know if it was a mistake I'd made, or if the aerial was completely incapable of picking up Winter Hill.

    With a new set-top box, we worked out that it wasn't the aerial at fault, but then with the new Humax I had yet another designed-by-autistic-engineers-in-another-language interface to wrestle with in order to tell the stupid box to tune into Granada and not S4C.

    If they're going to screw around with the retuning again, I may as well save myself the £100 train fare back to Liverpool and get a satellite dish installed. Oh wait, I can't because they live in a conservation area...

    AAAAAAAAARGH!

    1. Gareth Gouldstone
      Happy

      Thank God (or the council) for conservation areas

      Otherwise whole areas start looking like a Large Array Radio Telescope

  29. Anonymous Coward
    Thumb Down

    RFI (Interference to you)

    Frankly it seems that the writer has no idea about radio. A proper band filter will chop out the signal at well less than 600hz, amateures do it all the time, just look at their repeater systems. Frankly if on a Frequency scope their transmissions should be stopped and them fined. I have to comply so why should not they and I go up to 12.5Kcs of my band edge. Sure if a TV antenna/ receiver has a poor filter, a filter will make a difference and sure if they were to live pretty much adjacent to the transmitter there may be a problem. But if they were to interefere with mine I would prosecute, maybe privately, one can still use the county courts, even for that.

    Interference is basically down to money, so you add the dots.

    1. Fr Barry

      Erm, no...

      "A proper band filter will chop out the signal at well less than 600hz, amateures do it all the time, just look at their repeater systems."

      The 144 MHz band uses 600kHz spacing but when you get up to 430 MHz we use 1.6 MHz spacing. At 1300 MHz this increases still further to 6MHz spacing. This is done with very expensive filters at the repeater site not at the "consumer" end of the link. The cost of installing cavity filters at thousands of homes would be astronomical plus, they will need regular retuning to maintain optimum filter shaping (dropping one will mistune it for example)

      Commercial operators use much wider frequency spacing because it is then possible to use cheaper filters (and they have the frequency allocations to do it.

  30. illiad

    Graham Anderson:

    WTH not invest in a decent cable system, or even a 'stealth' SAT system - many installers will paint on a 'brick effect' or similar, there is also a dish that is designed to look like a garden ornament, among others... surely they could help....

  31. illiad

    @Mike 137: clearer...

    a better way is ..

    a 'perfect' filter is a cliff, ie straight up!!

    most filters are a hill... the steepness depends on design and has other problems, like 'Pyers' said..

  32. illiad

    Peter Gathercole:

    I think he is saying "users who've plugged them into their own televisions" to to exclude those who have a box sitting doing nothing due to your brand new TV, or just not connected due to the freesat part only being used... there is a difference!!

  33. illiad

    what ofcom annouced *last week*...

    "C61, C62 clearange and the 4G broadband sale"

    http://www.ukfree.tv/fullstory.php?storyid=1107051813

    "Ofcom moves to protect Freeview interference from 4G mobile devices"

    http://www.ukfree.tv/fullstory.php?storyid=1107051834

    Oh, and tech heads please note that though the site has good info, the guys answering comments does not seem to do tech, hates links, and will ban anyone confusing him ... :(

    there is already a good forum here, and digitalspy.. :)

    http://forums.digitalspy.co.uk/showthread.php?t=1485127&highlight=4g

  34. reichert

    Free view failure

    I live in Blandford and we have our signal boosted from a transmitter on the isle of Wight for the last two months we have been unable to receive channels 3,4,5,6,13,14,28 we have retuned on a number of occasions and sometimes the channels disappear altogether I have talked to other households and they don't seem to have a problem we also get problems with high pressure and sometimes when its just sunny also we don't get a very good signal on Sundays which is pretty random can anybody explain this phenomenon.

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