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Even the DNO get it wrong sometimes.

Kelly Marie Angel

Just recently there's been a lot of clicks and buzzes on my mediumwave listening set up  I tried to trace the cause  checking my station earth an RF earth not mains my areal and all the mains connection but all seemed OK. Anyhow after a few days I found the DNO had dug a hole in the next street and replaced a straight through  joint. I was hoping it had cured the noises but sadly not. About a week later they dug another hole replaced 3 joints in a space of only 50 feet 2 straight through joint and 1 splitter joint I think that's the right name for it. Finally the noise was cured but do the DNO  really look for noise or are they detecting something else like heat or vibration??

Parents

  • You could well be right about RF levels around Orford Ness I seem to remember that the cobra mist radar radiated about 3 Megawatts at various HF frequencys so would of created  RF spark hazards  even a distance away. Reminds me if a story I heard that construction work on a new sports stadium in arabia  was hampered by RF sparks from a metal crane hook caused by pick up from  1200Kilowatt mediumwave transmitter about a mile away! I never heard downtown radio on 1026khz here because radio Jersey uses the same frequency at 1 kilowatt its around 90 miles from here but is mostly a sea path  so it come in here with a surprisingly strong signal

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  • You could well be right about RF levels around Orford Ness I seem to remember that the cobra mist radar radiated about 3 Megawatts at various HF frequencys so would of created  RF spark hazards  even a distance away. Reminds me if a story I heard that construction work on a new sports stadium in arabia  was hampered by RF sparks from a metal crane hook caused by pick up from  1200Kilowatt mediumwave transmitter about a mile away! I never heard downtown radio on 1026khz here because radio Jersey uses the same frequency at 1 kilowatt its around 90 miles from here but is mostly a sea path  so it come in here with a surprisingly strong signal

Children
  • in reply to Kelly Marie Angel

    One of the situations were RF can be an ignition hazard is where you have a conductive loop in the RF field, that has an internal length about 1/2 the wavelength of the RF (≈ 94 m - 283 m for the MW broadcast band) and that loop is then broken, potentially causing sparking at the break.

    I don't have a copy of BS 6656 here at the moment, but I do have a vague memory of a diagram in it showing exactly that situation with a crane lifting a load, part of the loop made up of the crane jib and lifting cable etc.

    I'm recalling all the above from memory, so no-one reading this should use it as the basis for any safety critical decisions! Slight smile

    Downtown Radio on 1026 kHz, as well as being relatively low power I think was also beamed towards the west / north-west to cover Belfast and beyond, which would also have reduced your chances of hearing it.

    - Ross

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