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Freeview Issue

Discussion in 'Home Cinema & Hi-Fi' started by Wardyp, Feb 12, 2020.

  1. Wardyp

    Gangster

    Joined: Apr 8, 2008

    Posts: 377

    Location: Bratfud

    I've been getting messages on my TV all week about I would need to retune today as there is an update coming.

    I have retuned my TV's today and I have now lost all ITV/Ch4 channels and the HD ones too, anybody else had this problem today? It can't be signal related as they were fine yesterday and I can see the transmitter from my house.

    I'm in the Yorkshire region btw
     
  2. jpaul

    Capodecina

    Joined: Mar 1, 2010

    Posts: 10,904

    yesterday they have changed the channels for some of the stations .. so I retuned mine.

    if you know which transmitter you use, go to this site, find your transmitter, and it will tell you which channels you should be tuning in, and then tune then manually, via channel numbers site gives.
    https://ukfree.tv/transmitters/tv/Sandy_Heath#

    or, can go here too https://ukfree.tv/prediction and with your postcode it should tell you the expected transmitter
     
  3. lucid

    Soldato

    Joined: May 29, 2010

    Posts: 5,321

    Location: Cheshire

    Check first for dodgy wiring in any home made aerial plugs. Also, if you're using those thin coax flyleaf bought from supermarkets, DIY sheds and online retailers etc, then they can be a source of frustrating problems.

    You say it can't be the signal, but unless your aerial fell down or twisted overnight,or you found bad plugs/wires then the signal is exactly what the problem is. That's the thing that changed. It may be that the mux for the channels you lost is now at a frequency where your aerial sucks.

    More specifically, it's your aerials' ability to pick up the frequency relating to the mux (group of channels) that is now missing. This could either be because the aerial is a type that has a narrow channel range focus, or there may be a filter in place to block certain frequencies.
     
  4. Raggs

    Wise Guy

    Joined: Sep 5, 2008

    Posts: 1,325

    Location: Karazhan

    lost 9 hd channels in Sheffield on the 5th of feb :( this is due too technical changes to do with 5g roll-out plans.

    info i found on freeview.
    Unfortunately, it is no longer viable to broadcast some channels from Sheffield due to the complexity of the changes required to update TV signals.

    we still have channels 101-105 in hd tho. they chucked us a bone by saying the lost channels are still available in SD :rolleyes: lol i'd rather turn the tv off than watch something in sd on a 65 inch tv.
     
  5. Wardyp

    Gangster

    Joined: Apr 8, 2008

    Posts: 377

    Location: Bratfud

    I doubt it's a problem with the wiring as I installed it new 4 years ago (i'm an electrical engineer so hopefully I know what I'm doing :p ) and the transmitter is less than a mile from my house so that won't be an issue.

    I did notice that the TV is showing 100% Signal strength but the Signal Quality is pretty much non existent.
    I'm assuming they moved the signals to a band that either my aerial or distribution amp doesn't like, i'll have to do some more investigation.
     
  6. lucid

    Soldato

    Joined: May 29, 2010

    Posts: 5,321

    Location: Cheshire

    With respect, just because you're qualified in one aspect of electronics, it doesn't follow that you're also qualified to deal with aerials. I have been to plenty of installs done by qualified electricians where they've made a balls-up of it without realising; and I'm not talking about minor problems here. I've been doing this professionally for over 15 years, and there's still new stuff that I learn.

    You may have done a good job with your own installation at the time, but in this game experience counts for a lot too. Unless you've done a lot of installations and troubleshooting, you probably won't have encountered the quirks that crop up if your experience is based on just your own install.

    For example, sheath stretch (oo-er, sounds a bit rude, lol). This is where budget coax has a habit of the outer insulation stretching to a point where the inner insulation and core lose contact with the coax plug. Visually, the plug looks fine; but electrically the connection goes intermittent.

    This isn't the problem in your case. You've got lots of signal. This is just an example of things you come across after spending time in the field.

    You wrote that the transmitter is close and you've got 100% Signal strength but the Signal Quality is pretty much non-existent.

    To me that's an instant flag that suggests to look at overamplification.

    You might not be actively amplifying your signal, but using an amplified splitter in the form of a powered distribution amp does include 2-3dB of amplification per leg to help with cable losses on long runs.

    Where the local field strength is already generating a signal strength at the aerial that is close to the upper threshold for the tuner in your TV(s), and combined with the higher power of the public service (PSB) muxes, it's possible that the shift in frequencies has put a higher power PSB mux at a point where there aerial is more efficient and you've now got an overload. This is the effect of the digital cliff on the upper end of the signal threshold.

    The answer is a signal attenuator.

    Screwfix and Toolstation both have stores right across the country. They're open 7 days a week. Each sells 0-20dB variable attenuators. These are a great troubleshooting tool, and cheap! They cost about a fiver.

    Put one in line with the signal at the TV aerial socket. With the TV displaying Strength and Quality for the affected mux, increase the attenuation and watch the readings. As signal strength drops I would expect to see Quality increase.

    Let us know how you get on.
     
  7. Wardyp

    Gangster

    Joined: Apr 8, 2008

    Posts: 377

    Location: Bratfud

    I'll grab one from Tool station and see what occurs, thanks for your help.
     
  8. jpaul

    Capodecina

    Joined: Mar 1, 2010

    Posts: 10,904

    *warm boot*
    Are there any reliability disadvantages to the variable ones, versus a fixed, say 6db one ?

    I realise that with a fixed, if it is too much attenuation you could push out some muxes with poor reception, trying to fix the over-powered ones.

    perhaps I need to look at the response of my aeriel too, since the muxes that work, and, those that are pixellated(with > zero error rate) are all transmitted at 170KW according to freeview site.
     
  9. lucid

    Soldato

    Joined: May 29, 2010

    Posts: 5,321

    Location: Cheshire

    The obvious things are knocking the control so it gets turned up or down, and the percentage error at very low adjustment values.

    Fixed attenuators get around both issues, but as you say, if say 6dB is too much...

    TBH though, the 'acceptable signal level' window is massive. Way-way-way bigger than 6dB. The lower level is 45dB and the upper level is 65dB, so that's a 20dB gap immediately. These limits include safety margins too, so in reality you can expand both ends by another 5dB reasonably safely; so now you have 30dB to play with.

    The upshot of this is that in your case with 170kW across the board, the aerial would have to be something with an extreme gain curve, and combined a huge spread in signal range right across the channel spectrum, to get too much signal at one end that that when you fix that with some attention it then jeopardises reception on the main set for the lower-channel muxes.

    I can imagine problems for people when the signal then goes on to be split for other TVs in the house, or where the aerial is in the loft which means that the rain margin becomes a factor, or where there are deciduous trees in the direct line of sight to the aerial, or where some mules are very low powered compared to the main PSB ones. This is not an exhaustive list, but it highlights different scenarios.

    The bottom line here is that a variable attenuator is a very low cost diagnosis too, and a bloody useful gadget to boot.

    They're a fiver - or are at the time of writing - so even if you decide then to swap to a fixed attenuator, you won't have broken the bank with the variable one, and the chances are you'll have learned something about the way signals work by actively twiddling the little adjuster. That's got to be a good thing, don't you think?
     
  10. jpaul

    Capodecina

    Joined: Mar 1, 2010

    Posts: 10,904

    Thanks, OK I'll get a variable one ...
    indecision was partly that the variable ones are only a £1 more than fixed, so, were the £5 variables poor quality
     
  11. lucid

    Soldato

    Joined: May 29, 2010

    Posts: 5,321

    Location: Cheshire

    Not at all. There's a minimum cost to make, market, support and sell any product. In the case of the attenuators, fixed and variable, the base costs must be faily similar. For the fixed and variable attenuators I have, both styles look like there's siome hand assembly involved with soldering discrete resistors in place either inline or as a shut to earth on the variable potentiometer.
     
  12. jpaul

    Capodecina

    Joined: Mar 1, 2010

    Posts: 10,904

    seems to have improved situation ... leastaways, last night, anyway.
    on max attenuation, indeed, some channels broke up.

    couple of caveats I had seen before purchase ... these cheaper attenuators, have a specced minimum attenuation that may be 2db, and no dc passthrough.


    purchased from cpc , usually better prices than amazon too, when I rememember.
    [​IMG]
     
  13. varkanoid

    Sgarrista

    Joined: Dec 31, 2007

    Posts: 9,893

    Location: The TARDIS, Wakefield, UK

    thats the one I got when I had problems with HD 101-105 cost me £6. Fitted it then slowly tested it by going from 100% down and settled at 93% now no break ups on the HD channels. Think I have had it 2 years now and still going strong.
     
  14. lucid

    Soldato

    Joined: May 29, 2010

    Posts: 5,321

    Location: Cheshire

    There's an insertion loss whenever something is added in-line. That even extends to simple connectors. When calculating system levels it's usual to allow 0.5dB per joint for each F-type or coax connector, so 2dB insertion loss for what is two coax connections plus the PCB track of the attenuator sounds about right.

    The attenuator itself will still have a 0-20dB function plus the 2dB insertion loss. The crucial thing though is that it adds no noise.