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Will a 4G filter solve my interference problems

Discussion in 'Home Cinema & Hi-Fi' started by Taxboy, Feb 10, 2018.

  1. Taxboy

    Associate

    Joined: Jan 25, 2014

    Posts: 30

    Thanks for that. Unfortunately I don't have a suitable length of lead. I don't think its an amplifier problem as the TV upstairs is working well ...famous last words. I've just been notified the attenuator is on its way so will report back soon
     
  2. edGfaCTor

    Wise Guy

    Joined: Feb 27, 2009

    Posts: 1,117

    Location: Northamptonshire

    I wouldn't go back to that guy you have been using he sounds like from the way you have described it someone who is trying to make money of you it's cheeky to charge someone call out when they have had work done not long ago.

    Did he even go through the frequencies to check for signal in each location of your home?
     
  3. lucid

    Mobster

    Joined: May 29, 2010

    Posts: 4,247

    Location: Cheshire

    Thanks for the background info. Always useful.

    I am more reassured knowing he had a proper meter.Still slightly puzzled though why it wasn't used to do some diagnosis work. When metering at the TV points the target is 55dBuV, but anything from 45 to 65dBuV will generally work without issue.

    Your installer was right though, house builders nearly always seem to use the worst quality coax and aerial ancillaries for their builds. Maybe they figure what the eye don't see then the heart won't grieve over? It's stupid short-term thinking when the difference in price on a whole house install is less than £30. That's a drop in the ocean against the price of a new house.
     
  4. varkanoid

    Sgarrista

    Joined: Dec 31, 2007

    Posts: 7,857

    Location: The TARDIS, Wakefield, UK

    Just been reading this with interest. When you mean the TV is working well upstairs do you mean it has zero interference yet the TV downstairs has the interference ? If thats the case sounds more like the TV downstairs doesnt like the strong signals ?

    I have a BT TV UHD box and and BT TV HD box. On certain channels on the UHD box particularly on the HD channels I was getting breakup. However the BT HD box was fine. So I did a lot of googling and turns out the BT UHD box does not like strong signals. Sounds illogical doesnt it. It was at 100/100 (same as your 10/10). So I bought an attenuator from Maplin which has a variable gain on it so I can turn it up/down. I turned it down so my UHD box was registering 70/70 and the breakup disappeared. So I slowly turned it up as I was interested to see how high it would go before breakup. Around 92/93 it re-appears. So I turned it down to 90 and there it has stayed. I suspect you may have the same success.

    Although saying that it could end up being the age of the TV and if you buy a new one the problem will go away anyway.
     
  5. Taxboy

    Associate

    Joined: Jan 25, 2014

    Posts: 30

    Yarkanoid

    Thanks for your input. That's exactly what's happening so I'm hoping the attenuator I was recommended on here will sort out the issue.

    To get the purchase of a new TV past the senior financial controller I need to get this issue solved first. I have to agree with her that it doesn't really make sense to splash out a not inconsiderable sum on a new TV (plus new DVD player) if you can't even watch ITV. If I at least can get this working I can then move on to phase 2 which is moving the BT recording box downstairs, which I think will require the use of power line adapters..... but that's a whole new issue. Don't you just love technology ??!!!
     
  6. Taxboy

    Associate

    Joined: Jan 25, 2014

    Posts: 30

    Well having tested out the attenuator I am pleased to report it seems to have fixed the issue ;).

    I would like to thank those who have taken the time and effort to help me solve this issue. Great forum !!!
     
  7. Taxboy

    Associate

    Joined: Jan 25, 2014

    Posts: 30

    Just as you thought it was safe etc etc the interference has returned...... grr

    I have the variable attenuated on max so estimate signal strength about 8 with quality still at 10. The interference is now not so frequent or severe. Is there any other potentially cheap fix or will I have to get the aerial guy out ?
     
  8. jpaul

    Mobster

    Joined: Mar 1, 2010

    Posts: 4,470

    How frequently/times-of-day does the problem occur, and if you reduce the attenuation/remove-it do you get much more of the same type of interference ?

    which attenuator did you get ? (I had spec'd a constant one https://www.amazon.co.uk/gp/product/B003YKSRRG rather than a variable from an anonymous brand)

    ... you still need to eliminate the tv's .. so swapping the tv's would show whether lounge tv would have the same problem in the bedrooom and vice-versa
     
  9. Taxboy

    Associate

    Joined: Jan 25, 2014

    Posts: 30

    Thanks for your help I'll have a go at bringing the upstairs set down but may have to wait for the weekend.
    On my phone at the moment so will link to the attenuator I got when I get home.
    I don't watch TV during the day so have done limited testing at the weekend - there's only so much rerun of light entertainment I can stand ! However from a totally unscientific test the issue appears to get worse in the evenings say from 20:00 onwards
     
  10. lucid

    Mobster

    Joined: May 29, 2010

    Posts: 4,247

    Location: Cheshire

    Just a quick recap

    - You live somewhere in the Anglia TV region
    - Your main transmitter is Tacolneston
    - You have a loft aerial
    - There's a multi-way splitter fitted in the loft too
    - The house had aerial cable installed in-wall by the house builder, but you've had a new piece run by an aerial guy which did temporarily fix the interference issue [this could be coincidental]
    - The issue affects only the lounge TV
    - The issue affects only Mux c59 (PSB2 D3+4)
    - Signal strength and signal quality were both at 10 on the Panasonic TV's meter
    - You've done the postcode checker at 4G AT800 and it predicts no issue with mobile phone mast interference
    - Following advice here, you've bought and fitted a variable attenuator. It is set to max. Signal strength 8, Quality 10. This improved things for a while but now you've got some interference creeping in again
    - The issue is worse at night


    My gut reaction is you've still got too much signal coming off the aerial. Solution: Add a 10dB attenuator and turn down the variable until the problem stops. i.e you might need 22dB of attenuation, so the variable alone (if it's a 20dB attenuator) isn't quite enough. If you look at the sensitivity of a typical wideband high-gain aerial they have a rising hump (see the graph in post #6). That means they put out most signal strength at the upper-end of the channel range. Look at how that tallies with your experience: Your issue is with c59, but not 55 or any of the other lower channel numbers. But that's not the whole story.

    Adding a 10dB in-line attenuator is easy. However, you run the risk of fixing one problem and causing another elsewhere.

    Referring back to that sensitivity graph in post #6, you can see that the wideband high-gain aerial is poor at lower frequencies. Your family's main TV is already picking up on c45 and c42, but you seemed to be missing out on c39 before the attenuator was fitted. Throwing in yet more attenuation could put c42 & 45 at risk as well.

    With this in mind, and factoring in that over the next couple of year all the channel space from c49 to c60 will be cleared ready to be sold off to mobile phone companies, then the outlook for your current aerial isn't great. All the TV transmitters will eventually go to frequencies that are c48 and lower. It's ironic that it'll fix your c59 reception issue, and probably move those channels to somewhere you can't get a signal.

    The bottom line is that sooner or later, just like tens of thousands of other homes in the UK, a wideband high-gain aerial of the type being sold as a "universal aerial" for the last 20 years is going to become junk. A Log Periodic aerial is good for now and for the future when the channels all move to c48 or lower. Fitting a Log now will also fix the over-saturation at c59.


    There are two other areas I'd look at just to dot the I's and cross the T's.

    1) The aerial position in the loft. Ideally, move the aerial to outside. But if it has to be in the loft because of some covenant on the building then the installer must really spend some time measuring and mapping out the signal levels across the loft space. It's not enough to assume that the middle of the loft is the best place.

    2) House builders use cheap aerial gear. That goes for the wall socket plates as well as for cable. If you haven't already had it changed, swap out the wall plate for a shielded version.


    Finally, the time of day (or night) could indicate that your site is experiencing a phenomenon called tropospheric propagation. ("What?" I hear you say :D ) It's radio signals (and yes, TV is part of the radio spectrum) bouncing off a boundary layer within the atmosphere. Folk who listen to short-wave radio take advantage of this phenomenon all the time. Due to the curvature of the earth there's no direct line of sight to distance places such as Russia, and since radio signals only travel in straight lines then it shouldn't be possible to pick up from- or transmit to- places beyond the horizon. The surprising thing is that the horizon is much closer than you think. For a 6ft tall person at ground level it's only about 3 miles away. This is why transmitters are very tall and why getting the receiving aerial up high makes a difference.

    TV signals work at much longer wavelengths than SW radio, so this bouncing effect is far less pronounced. A lot of the signal just passes straight through the atmosphere on on eventually in to space. However, in the right conditions then the signal from distant transmitters can be detected, and the signal from local transmitters can become a little bit stronger. Night time is typically when this happens. The result; if your signal was already borderline 'too much' then this small boost could be enough to tip the balance.
     
  11. Taxboy

    Associate

    Joined: Jan 25, 2014

    Posts: 30

    Thanks for taking the time to explain all this. I do like to try an understand why things happen - try being the operative word. Just to correct a couple of points :

    The aerial is outside attached to our chimney the splitter an booster is in the loft

    The new aerial feed doesn't have a plate the cable comes in through the wall with a grommet to seal around d the hole inside.

    Based on what you have said I think I will get another attenuator - if it creates more problems than I can always run ITV through the digital recorder. It drops the quality a touch but on an old 720 TV I can live with that. If I get a new TV then I can budget for a new aerial as you suggest