Phone connection with BT Infinity

Discussion in 'EMC Matters' started by moci718, Jan 4, 2018.

  1. moci718

    moci718 New Member

    When BT Infinity was installed a new overhead cable was put in. (Black round 4 wires). This comes to a junction connected directly to the old phone wire which runs through the loft and house to two BT phone points. (Grey flat 2 wire like 45 ohm feeder). At the junction the black cable continues to the broadband box which has a phone socket (unused). I presume the old phone wiring should have been connected to the broadband phone socket or a filter fitted to stop radiation from the old phone connection which I think is my problem.
  2. Ken G3SDW

    Ken G3SDW Moderator

    But you do not say what your problem is, could you share it with us please.

    As well as that could you share with the forum your name and perhaps your call sign.
  3. moci718

    moci718 New Member

    OK Ken. Jim King G5TA Ewell Surrey.
    A few months ago BT sent an email saying my broadband speed will increase. It did from about 25Mbps to 50+ on occasions. I have S8 of noise on 20m without the pre-amp in. I only operate on 10/15/20m with a vertical but below 20m seems just as bad. A portable receiver shows an increase of white noise approaching any mains wiring in my house and next door. So I do not know whether the noise is mains-borne only. Seems stongest near the broadband box. Next door also had a new overhead cable at the same time running parallel with mine and then on to their house.

    To complicate things I have a second problem:
    I have an Ignition-type noise that wipes-out the BBC World Service on frequencies 6195MHz, (12095 and 15575 not so bad.) and appears to peak around 17.55 MHz.
    I have been unable to trace the source in my house but it appears to be mains-borne and is the same near mains wiring in my neighbours house.
    Any clue as to likly source would help me trace this.
  4. Ken G3SDW

    Ken G3SDW Moderator

    Well if you go close to any mains wiring of phone lines then you will get much increased noise Jim.

    To be totally safe then you will need to turn off your mains supply and check to see if it is still there, if it is then ask your neighbour if they would not mind helping you to do the sane thing.

    Its obvious that you both have VDSL and for some time at the EMCC have been investigating problems concerning similar problems like yours.

    Does the noise go when you turn off your router, you also say that you feel that it is mains born, are you saying that when your antenna is disconnected then the problem is still there, if not then it is not mains born but simply conducted into the mains wiring and re-radiated, this being quite common with problems today.

    Get back to me if you could and we will see which way to go.
  5. Ken G3SDW

    Ken G3SDW Moderator

    No in most cases such as this it is because there are phone cables out of balance, mainly due to bad high resistance connection on drop wires, in your case they are both new so that will not be the problem, also multiple extensions within the home will also throw the system out of balance.

    By just turning off individual bits of kit will not totally prove anything so once the bread making and no doubt eating lol then turn off the mains and check on yu portable RX.

    The old wiring maybe, if there are any high resistance connections be a problem and the only way you can prove that is to have it replaced along with new boxes along the way.

    It is going to be a trial and error job Jim as the only way is to isolate the problem from either you or you neighbour.

    I can smell the bread from here so enjoy and let me know how you get on, always here to help at all times.
  6. Ken G3SDW

    Ken G3SDW Moderator

    Jim take a read of this, it may help you understand what problems VDSL can cause and a check to see if the frequencies involved are applicable to you.

    The EMC Committee is carrying out an investigation of the significance of interference to amateur radio from leakage from VDSL systems. The emissions from VDSL are continuous and indistinguishable from white noise and may go unnoticed.
    VDSL2 covers frequencies up 17.66MHz. The downstream and upstream bands alternate and the easiest way to detect VDSL is to look for the change in noise level at the band transitions. These are nominally 0.138MHz, 3.75MHz, 5.2 MHz, 8.5 MHz, 12MHz, and 17.66MHz. The band that predominates depends on distance of the house from the street cabinet. Most problems are seen when the connection to houses in the area is by overhead cables.
    The effect will be that received signals seem weak and the background S meter reading higher than expected. To check for VDSL emissions tune about 75kHz either side of the nominal transition frequencies. Ignore off air signals and local incidental noise. Tuning around these frequencies and listening while watching the S meter will show a noise step if there is VDSL interference. If an SDR is available the step will be clearly seen and the 4.3125kHz patterning of the VDSL signal may be visible on a waterfall display, but careful adjustment of the contrast may be required for this.
    If you want to see some examples look at the 2014 RSGB Convention paper http://rsgb.org/main/files/2013/10/2014-Convention-EMC-paper-emerging-threats-v5.pdfThere is also an item on VDSL emissions in in EMC Matters in RadCom December 2013.
  7. moci718

    moci718 New Member

    Thanks Ken. Noise level certainly higher around the frequencies mentioned. An hour ago 15 and 10m were s1-2 suddenly I now have s8+. 20m consistently s8 white noise (no pre-amp).
    Power turn-off made no perceptible difference in the shack (outside 15m from house). Walked to the pole in the street (70m away) some hash from the down feed but not much. This feeds mine and 2 other houses by overhead wires.
    The popping noise puzzles me (6-17 MHz). It is loud in the house till the power is switched-off but then it is detectable on the overhead cables to me and next door. The noise is being conducted into my sky-box and TV through the LAN cable. Power down the openreach box and the noise in the house goes but still on the outside cables.
    All I have found is a noisy motion-sensor security light.
    Power-down was a bit delayed as the wife had a sough-dough starter brewing which takes 26 hours in the machine!
    I am going to try disconnecting the phone feed which is connected directly across the overhead cable, as you say this may be unbalanced and radiating under the vertical.
    Jim.
  8. Ken G3SDW

    Ken G3SDW Moderator

    Yes Jim carry on as you are going in the right direction and make sure that you disconnect the phone line going to your sky box.

    I am assuming that when you say power off you mean totally off at the fuse box, the house being totally dead?
  9. moci718

    moci718 New Member

    Yes power totally off. Disconnected the branch to the telephone made no difference. I just have BT phone Sky box is for satellite only. Fair bit of hash around all broadband connected devices when close. Switching them all off makes no difference to reception in the shack. My vertical has tuned drooping radials with the base 20ft above and to the side of the overhead cables so I guess I am on a loser here unless I can re-site the aerial sytem. Popping sound on the BBC world service frequencies puzzles. At first I thought it was jamming but definitely from the broadband.
    73 Jim.
  10. Ken G3SDW

    Ken G3SDW Moderator

    OK Jim, not sure at this point regarding your popping noise on BBC world service but that must come second to me trying to help you regarding amateur bands, let us tackle one problem at a time.

    As i have said before going close to and devices that you have will always increase noise, they all generate it but should not radiate very far at all.

    I think now and as you have said that this only started since you have had your BT broadband speed increased and overhead drop wires replaced then you will need to contact John Rogers M0JAV who is the chairman of the EMCC who totally is involved with helping VDSL complaints, you can contact him at emc.chairman@rsgb.org.uk explain to him that you have talking to me on the Interference forum and give him as much info as you can, he will need you to do some specific tests.

    He is a very busy chap but will reply to you asap.
  11. moci718

    moci718 New Member

    Thanks Ken, have been in contact with John and tests for the survey done. Looks like the 20M problem arises because I am only 100M or so from the cabinet and the local feed is all overhead. Pity we don't copy the French with overhead fibre. I am informed they also run fibre through sewers!
    Jim.
  12. Ken G3SDW

    Ken G3SDW Moderator

    Thanks for letting the Forum know Jim, good luck mate.

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