20 metre Intereferenc

Discussion in 'Interference Problems' started by Graham Allen, Jan 16, 2018.

  1. Graham Allen

    Graham Allen New Member

    Hi. Over the Christmas period I observed severe interference on 20 metres. I do have to admit that I only use this band once in a Sheffield flood. I have tracked the source of the interference down to my neighbours PLASMA LG television. He is a very amiable guy, so I said I would do some research to find out what part of the TV might be generating the interfetence, my guess would be the SMPS but I am no expert in this field. If it is the SMPS I guess the first thing to do would be to fit some type of ferrite core to the mains lead, just not sure what type & how many terms. I will attempt to attach a screen shot of the interference.
    Regards Graham. DFF71473-CCA4-439D-83E7-689602345B14.jpeg
    Ken G3SDW likes this.
  2. Ken G3SDW

    Ken G3SDW Moderator

    Sorry to be the giver of bad tidings Graham but this problem with Plasma TV no matter what make it is once it reaches a certain age is quite normal.

    It is not faulty but doing just more than it should as once it gets to a certain age , something like 2 years plus then the Plasma panel starts to drop in output and the drive to the panel is ramped up causing spillage from the glass seals around the edge of the panel.

    There sadly is no cure to stop this other than to replace the TV, i know this as many years ago in my position as an EMC adviser tackled the problem with the three manufacturers ie Samsung, Panasonic and LG, other than LG then the other two agreed to replace the TV with an LED type at no cost but sadly LG just did not want to get involved.

    This arrangement lasted for several years and manged to get replacements for a vast amount of amateurs some sets being there own and some who had two sets all with no problem at all.on a couple of case i managed to arrange for this to be done in Scandinavian and one in New Zealand.

    No amount of ferrites will stop this very bad noise you are getting so my advice to you and it is entirely up to you is to offer to go half way to purchasing a new TV for you neighbour.

    Sorry Graham i know this is not what you wanted to hear
    Last edited: Jan 17, 2018
  3. Graham Allen

    Graham Allen New Member

    Hello Ken

    Thank you very much for responding so quickly to my post.

    As I said it is not the end of the world for me if 20 metre band suffers from this interference from around 16.30 to 21.30 hrs, as if I am in the shack during that period, I would normally be playing with 2 mts, 70 cms & 23 cms. However it would still be nice to be rid of the interference, but going by your past experiences and many of them, then as you said I will have to live with it. What I don't understand is, I have been the owner from new (about 9 yrs old now) of a Panasonic 55" 3D Plasma TV which radiates very little EMC products and causes me very little interference, if I go close with my handheld it is loud, but move a few yards away and it significantly drops off, so as my neighbours TV set is some 10 metres away from me, then how come it can radiate much further than mine or is this radiation being picked up by the mains supply then radiated around. The three bungalows are fed from and overhead supply and when his TV is on and I go out to the electricity supply poll and hold my handheld about a metre away from the up feed cable before it splits 3 ways (to feed the 3 bungalows) the interference is very bad indeed. I have carried out this same test on all mains feeds entering the respective bungalows a get the same level of interference. So is there the slightest chance that the interference is being transmitted out of his TV via their mains cable. I rather suspect you are going to tell me that from the screen shot I sent you proves conclusively that it is being radiated by the screen and not a product of the SMPS coming back down his TV mains cable and thereby going to the trouble of using ferrite cores would be futile.

    There is a glimmer of hope as during the conversation with my neighbour I told him I was seriously considering buying an LG OLED TV (that remains to be seen after your comments about LG not being very helpful) which he replied that his Father-in-Law had recently purchased an OLED TV and that he was mightily impressed with it, so much so, he was considering changing. FINGERS CROSSED.

    Best Regards

    Graham G8LZG
  4. Ken G3SDW

    Ken G3SDW Moderator

    Well Graham you must have one of the very few Plasma TV`s that do not give a problem as 99% of them do, maybe it depends of how quickly the panel drops in output, your one obviously has not done so yet but it will.

    I must say the Panasonic and Samsung for that matter are by far better for radiating RFI than LG

    All that is happening is that when the panel seals break down then they do radiate and get conducted into the TV antenna and mains cable so they radiate as well.

    Lets hope your neighbour make the derision to upgrade to another TV and if i where him i would not go for LG, basically as if he had a problem under warranty then they are not very helpful at all, there are many other brilliant makes of the type of TV he is considering, and being before i retired was in the TV servicing trade for well over 50 years, and still actively watching trends of todays products, if i can be of any help then just shout, my email is OK on QRZ.com
    Last edited: Jan 17, 2018

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