Strange Freeview and analogue interference problem.

Discussion in 'Freeview & YouView' started by asdigi, Jun 12, 2008.

  1. asdigi

    asdigi
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    For a couple of years now I've been having interference issues with both analogue and digital freeview reception.

    On the analogue channels I get a very thin line of static flash up on all TV channels and anything else tuned in via RF. It is only about 1 or 2 mm thick and flashes up for a split second every 5 seconds or so and appears to circulate arround the TV screen. For example it will first flash at the top of the picture, then the middle, then the bottom, then just below the top, then just below the middle etc. etc. This happens most of the day, its very rare for it not to happen.

    I have put 2 TV's next to each other, one displaying an analogue channel and one with freeview. When this line of static flashes on the analogue channel it causes the freeview picture to break up or produce green and purple squares, also if i'm using one of the radio channels on freeview the sound makes a horrid crackle. The extent of the audio crackling or picture breaking up depends on how thick the line of interference is.

    This happens on all the TV's in the house and doesn't make any difference if I'm using the outdoor aerial or an indoor aerial.

    Any help much appreciated.
     
  2. LV426

    LV426
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    Firstly, the comparison of the effects of this on analogue and on digital are quite typical. The position of the flash on your analogue signal simply means that the timing of the cause, in relation to the image, varies each time.

    This seems like electrical interference. A frequency of once every 5 seconds would tend not to suggest a thermostat on some heating or refridgeration (which are common causes).

    I'm at a loss to imagine what might be switching itself every 5 seconds, but I guess you need to try and work it out. It may not be in your home; it could be in nearby premises. In any case, you should carefully consider anything of yours that might be the culprit. Turn things off at the mains one at a time to see if you can establish the source.

    Electrical interference like this is illegal; if the cause is yours, then you need to fix it. If it's someone else's (and they are awkward about it) you can have a fix enforced, I believe.
     
  3. bsuttie

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    You don't live close to an airport do you? I've seen similar from an airport radar system.

    regards

    Brian
     
  4. mrfreeview

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    Halogen or sodium lamp on a building nearby which is on 24/7

    Fish tank water pump?

    CCTV camera which is panning around all of the time?
     
  5. asdigi

    asdigi
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    Thanks for all the replies, very helpfull :) Over the weekend I will try to find if the interference is coming from in my house to start with.

    There is an airport near me but its about 15 miles away, but then the interference does vary each day and I understand that different weather conditions affect signals. When it is clear hear in the summer I can receive foreign channels on both analogue and digital tv but the interference is the same all year round.
     
  6. SamRadford

    SamRadford
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    If you can hear it on a detuned portable radio then it should be fairly easy to pinpoint the source (if local).
     
  7. scribbler101

    scribbler101
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    Don't know if it still applies, but you used to be able to get free investigation into apparent interference from the BBC as agents for the licensing authority.
     
  8. SamRadford

    SamRadford
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    BBC? Hee hee, you are showing your age. :)

    I recalled reading about this in a Satcure review. A quick search of their site for "interference" proved that my memory isn't so bad after all! This sums it up fairly well:
    http://www.satcure.com/reviews/review95.htm#01
     
  9. scribbler101

    scribbler101
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    I have a large, and increasing, amount of age to show. Lets put it this way - the first set top box I can remember was the one for ITV.

    Are you THE Sam Radford?

    The one quoted as saying "There ain't no such thing as a digital aerial"?

    If so, perhaps you can help me understand better. I realise that it is the signal that is digital not the antenna; but are there not particular types of antenna designed to receive particular digital transmissions? Aren't some horizontally and some vertically polarised for example?

    BTW; Nothing wrong with Yorkshiremen. Obviously they suffer a lifetime of angst at birth on t' wrong side o't hill; but if you can't be a Lancastrian it is a reasonable second best.
     
  10. fernandez

    fernandez
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    Sorry to jump on this....
    Yes, the poster AFAIK was THE Sam Radford.
    who runs this site
    http://www.sam-radford.me.uk/

    Both analogue and digital signals are transmitted with either vertical or horizontal polarisation. Aerials can be installed so that the elements are facing either way.
    Just as an aside......satellite signals can be vertical, horizontal or circular polarisation
     
    Last edited: Jun 20, 2008
  11. asdigi

    asdigi
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    For the past week or so I have had no interference :thumbsup: However I'm sure it will return and I will keep a log of when it appears again, thanks for the link below, I've bookmarked the ofcom link which I will probably use if when the interference returns I have proved it isn't coming from my house. :)

     
  12. asdigi

    asdigi
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    Well the interference has been back for a couple of weeks now and I have been unable to find whats causing it :( I can't hear anything on a radio, tuned in or not.

    How could I copy from a DVD to a file so i could then upload to photobucket? (If I put my DVD recorder on the VCR channel with the VCR in standby you can see the interference very clearly as the VCR outputs a black screen in standby on its RF channel) you might have a better idea of it if you could see it rather than just by my description. :)

    I have been reading about tetra filters so have purchased one of these Labgear amps with built in tetra filters to try. http://cgi.ebay.co.uk/2-WAY-PRO-AER...7102397QQcmdZViewItem?_trksid=p3286.m20.l1116 Thought its worth a go for only £15, if it doesn't work I'm sure it'll come in handy somewhere else if i need an extra aerial connection :)
     
    Last edited by a moderator: Jul 25, 2008
  13. radioredcat

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    Hi just a thought have you got any electricity powerlines near your house i had trouble back in 1980 when i was tv dxing and i got the post office to trace the interference as it affecting the local bbc 1 405 service the interferenc only affected band 1 did not affect radio services.The point is electrical interference can be frequency sensitive btw you have to pay to intference investigated by ofcom,ive just had another thought does anybody do any welding nearby like car repairs,you need to note times of the day to see if industrial or domestic also check all your plugs in the house.hope you get it sorted


    andy
     
  14. asdigi

    asdigi
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    Well the amplifier with built in tetra filters arrived yesterday and it has made no difference to the interference :(

    thats interesting thanks, there's nowhere nearby that does welding etc. however this has made me think about our electricity meter, we have had a few very high bills lately, 3 times what they normally are and I've been wondering if our electricity meter is not working correctly, its from 1967 and EDF said ideally they should be replaced every 20 years. I was thinking as it has dials that spin round all the time and that varies depending on how much electricity is being used, maybe when the dial spins round it arks causing the interference on the tv signal? or am i talking nonsense?
     
  15. Chris Muriel

    Chris Muriel
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    A standard ferraris disc electricity meter shouldn't cause any interference.
    Those old electromechanical meters are pretty simple.
    However, yours is long overdue a replacement - probably with an electronic one.

    Chris Muriel, Manchester
     
  16. scribbler101

    scribbler101
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    Were they "proper" bills based on usages, or payments derivd from estimates? Either way, record the meter reading daily and see if the wheel still turns with everything off.

    Cheers

    Steve
     
  17. radioredcat

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    Hi,chris is right about meters iv'e not heard of any causing interference,but if it is that old then it's likley that the cables and meter tails are past there sell by date.If there was a problem with the cables i think you would know about it eg lighs dimming badly when you put a kettle or shower on,but i doubt very much it has anything to do with the meter.Have you asked your neighbours if they are getting interference,in my last post i mentioned checking plugs because i have had interference from a loose wire in a plug the screws work loose over time the moulded plug type are ok in that respect.as for the electricity consumpion you need to check your readings i had a similar problem and i found that the freezer was responsible the thermostat had gone faulty and was stuck on making it run all the time.anyway keep us updated.

    andy
     
  18. asdigi

    asdigi
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    I had a breakthrough last night! [​IMG]

    Not sure what it is I've made but it seems to remove the interference and keeps the TV signal just as strong.

    I thought I would try an old indoor loop aerial on a length of coax and move it around the house to try and locate the interference, but I couldn't find anything, holding the aerial out the window near the outdoor aerial gave a good picture but still no interference, plugged the outdoor aerial back in and the interference was there, plugged the loop aerial in and no interference. So I then thought I would see how the aerial is constructed, at the loop end the wires are just joined to the loop but in the plug is was looks like a mini ferite? ring with the wires twisted round. Found out this is a balun. What i then did was take that off the lead and take another one off another loop aerial and joined the 2 together with some 2 core flex as they are 75 to 300 ohm plugs, connected this on the end of my aerial lead and connected to the freeview box. Hey presto the interference was gone and the tv signal was still strong [​IMG]

    This morning I put the tv on and the interference was nowhere to be seen [​IMG] took my homemade lead out and the interference was back!

    Here's a photo of what I made.

    http://s328.photobucket.com/albums/l324/asdigi/?action=view&current=DSCF1230.jpg

    I have another thread on the digitalspy forums regarding this problem and I have come to the conclusion my tv aerial doesn't have a balun which can help keep interference out, The new 32 element aerial I have ordered has a printed circuit balun so I'm hoping that will work without the need of my homemade lead! It should arrive today, will find out when I get home from work. I'm hoping I've solved the problem at last. :thumbsup: I've put up with it for long enough.
     
  19. radioredcat

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    Hi i think your getting somewhere now,that confirms you are getting rf interference i suspect you have made a crude highpass filter (passes high frequencies but attenuates the lower frequencies below the uhf band.if you put another aerial up it may not solve the problem as the coax will pickup the interferece the filter always has to be at reciever end,to confirm this theory is to try cb filter ideal if you know somebody that you borrow on off to save spending more money but they are easy to make.what i am suggesting is a to find out what cause is.If the interference is rf it looks like it could be (single sideband) which cb/radio hams use i am an ex cb enthusiast and i relied on nieghbours telling me that i causing interference.It could also be pmr/data interference aswell,and last there is a lot of wireless equipment around these days like older type doorbells/baby alarms ect they used vhf low band todays items use uhf.Hope this helps let us know how you get on and i'll my thinking cap on.

    andy
     
  20. mrfreeview

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    Actually I don't think you have solved the problem. I would suggest that the problem of interference is still "out there somewhere" what you have done is found a solution to mask it from your receiver.

    You could verywell find that when you fit your 32 element with balun that the problem will be back especially if the noise is being introduced into the down lead, saying that at least with an antenna with a balun you will have an impedance matched circuit.
     
  21. asdigi

    asdigi
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    You were right, I put the new aerial up at the weekend and the interference is still there :( The new aerial has helped though, the interference appears to be gone from analogue channels 1-4 and the channels looks perfect, never new an analogue channel could look so good, they were good before but not this good! ITV was a little fuzzy but now its perfect. However the interference is still visible on things tuned into the tv through rf such as a vcr or freeview box. Also on Freeview the interference is far less often so it hasn't been a complete waste of time purchasing and installing a new aerial. :)

    Also with having the aerial indoors for a while and not having any interference but with it outside I do get the interference I think It's safe to say the interference isn't from my house or from the mains supply.

    Thanks for that, I have purchased a CB filter to block TVI interference off ebay for £5 so I'll give that a go :)

    What sort or items would pmr/data interference come from?
     
  22. radioredcat

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    Hi pmr (Private mobile radio) meaning mobile radio communications services provided for non-public use, such as by emergency services,utility companies,pagers,taxi companies and transport companies also mobile phones.The frequencies used is vast covering vhf-uhf but i would have thought if your getting interference your nieghbours should be getting the same but i would wait now till you get the cb filter and hope it cures it.One thing i have just thought about is mobile phones the handset communictates with mast every so often because if i put my mobile phone near the tv i get lines across the screen on ch 4 uhf ch65 only just something else to think about.i'll wait to hear how you get on.

    andy
     
  23. Chris Muriel

    Chris Muriel
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    CB filters only work up to about 30 MHz (CB band is 27 MHz). One that attenuates everything below about 400 MHz would be more likely to cover the range. Many PMR systems are in bands between about 40 MHz and 200 MHz (certainly the older analogue ones).
    If you manage to find the actual interfering frequencies involved, a bandstop filter would be effective; the best ones have adjustable tuning (over a small range) so they can be optimised for maximum bandstop effect for the actual interference.
    I have in the past made these (to help clear blocking interference from my own amateur radio equipment at 432 and 144 MHz); helped a close neighbour out that way.

    Chris Muriel, Manchester
     
  24. radioredcat

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    Hi,your right chris about the cb filter but i should mention that i live only half a mile from a pmr/mod station and don't suffer tv interference but the amature bands are hopeless tones everywhere,i would say that the pmr station will take care on their transmissions,but some cb operators don't.I was also thinking along the lines of say a taxi firm or something like it which is operational most of the time,could do with some pics of this interference,asdigi08 did ask about pics this is the way i would do it record on dvd/copy that to the hdd/play with vlc which allows you to take snapshots/then convert it to jpeg,there maybe an easier way.

    andy
     
  25. asdigi

    asdigi
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    I remembered earlier I can take videos with my digital camera! :) I have recorded a video, its about a minute long showing my tv tuned to the vcr with it on standby where it outputs a black screen, you can clearly see the random lines of interference on there. The interference is the same accross all rf channels.

    http://s328.photobucket.com/albums/l324/asdigi/?action=view&current=DSCF1235.flv
     
  26. scribbler101

    scribbler101
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    I don't think it will win prizes, but it's a lot better than Big Brother
     
  27. radioredcat

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    Hi,that definitley looks like electrical interference iv'e seen enough of it when i was tv-dxing back in the eighties,that was at vhf fequencies but uhf is less susceptible to interference than vhf.from what you have said it looks like it's coming from outside your house.I know you said you tried a radio but i don't know what band you tried,what i'm going suggest now is to try an am=medium/long wave radio (but don't use fm) tuned to an unused frequency if possible connect the radio's aerial with a short piece of wire to the body of the tv aerial plug and see if you can hear the interference hopefully if you do pick it up you will know what it sounds like and then you need to go outside and possibly in the street.Is that interference there all the or is it sproradic.

    andy
     
  28. N.Dean

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    Perhaps you have made a "braid-breaker". This prevents any interference which is picked-up on the downlead from getting into the receiver.
     
  29. asdigi

    asdigi
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    Definately not CB interference then? I was hoping I would be able to sort it with a filter, oh well. I'll get the old portable radio out again and give that a try.

    Sam Radford did sugest buying a handheld tv but the trouble is the interference isn't very easy to spot on the normal analogue 1-4 channels, however its very clear on anything else tuned in via rf like a vcr.

    Lately the interference has been there most of the time, the only times i've seen it disapear in the past couple of weeks has been after the thunderstorm and when it rained the other night.

    I tried the little cable i made out of 2 75ohm to 300ohm plugs and some 2 core cable but whilst it doesn't weaken the signal too bad on analogue channels the signal is nearly half what it normally is on freeview.
     
  30. asdigi

    asdigi
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    If a braid-breaker is literally just not connecting the braid to the aerial plug, only the centre wire, then i did try that last night and the interference wasn't visible but the channels were weaker. Can you actually buy a braid breaker or are they only a diy item?
     

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