EMC multi-carrier issue

Discussion in 'Interference Problems' started by Pete Steadman, Mar 28, 2019.

  1. Pete Steadman

    Pete Steadman New Member

    Calling all hams!! Was wondering if anyone could help me shed some light on my mystery "replying" carriers? They appear once I key up. They are more irritating than a nasty invasion of crabs (I imagen). The symptoms are that immediately after keying up - CW in the video, but SSB too - I get a "reply" of multiple carriers that lasts five to ten seconds. Not having notch filters on my rig, you can imagine how annoying they are. The time I key up for seems to have an effect on the amount of carriers that reply. Longer equals more carriers. Also, it appears to only effect the 20m band.

    I have provided a link for Vemo where I uploaded a short video of my SDR waterfall demonstrating the problem. I start with a short press and over three key ups, increase the time of TX.

    Description below video: "Unsure what the "replying" multiple carriers are. They are more numerous the longer I key. Tried two 20m antennas with the same result. They are present on my SDR's waterfall and my rig. They are operating as two separate systems. Therefore, I'm confident that it's not a gremlin within my equipment. I suspect that it is VDSL interference but unsure."

    If anyone could enlighten me to whats going on it would be much appreciated!

    See link for video, it allows you to enlarge the screen to view it better. Please note: I had to add a space after https to display the link. otherwise it would only show the media window.
    https ://vimeo.com/327023708

    73 Pete M6LUW



  2. Ken G3SDW

    Ken G3SDW Moderator

    Hi Pete, thanks for using this forum.

    The video you sent, 1. what mode was you using?2. what power was being used and 3. have you listened to the carriers in CW mode, if so are they clean or have they any data on board.

    Have you turned off your mains supply yet and done the test again using your radio on a battery supply, that will prove that it is not something within your house, this is a most import thing to do at this stage.
  3. Pete Steadman

    Pete Steadman New Member

    Thanks for your reply Ken.

    In the vid I'm using CW, TXing with 10w, as if I was tuning up with an ATU. investigating the carriers they seem just that, no data seems present. The rig is running off its battery supply in the vid. Been round the house turning off then on electrical items. No joy.

    I forgot to mention the issue is intermittent, experienced it before. It lasted about a day then ramped down to a level that was not really a problem. Today though, they are so strong that I was missing the start of overs during QSO's.
  4. Ken G3SDW

    Ken G3SDW Moderator

    No dont go round the house turning off items you must power the house down completely or you will just be chasing your tail.

    From the details given and its a bit odd to be only on 20m as it may well be a newly installed VDSL system close to you going into its training, the symptoms are quite classic mode, it does this until it finds the bast way to operate for the end user then the symptoms disappear, this is quite normal.

    Things to do are 1. turn off your mains supply first and test again, if it is still there then 2. check for the same symptoms on 30m and tune to 10.104Mhz and try again.
  5. Pete Steadman

    Pete Steadman New Member

    Ok, going to power down in a moment and check 30 and 10.104Mhz. In all honesty, I didn't check thirty, just 40, 20 the main bands I use and 80 too. There is a pole about 15m away form my house, it looks to have around 12 to 13 properties hooked up to it. Fingers crossed!
  6. Ken G3SDW

    Ken G3SDW Moderator

    If it is that then it will be someone who has recently had VDSL installed
  7. Pete Steadman

    Pete Steadman New Member

    Just completed the power down test on 20 etc. and checked 10.104Mhz with and without power and there was no difference.
    30 is slightly different to 20. displayed in the picture of my waterfall there is a light band of noise shooting horizontally across the screen. This happens immediately after letting go of the PTT key. within it you can see four carriers, they are not normally present. Also, there is I pic of the pole outside mine.



    [​IMG] [​IMG]
  8. Pete Steadman

    Pete Steadman New Member

  9. Ken G3SDW

    Ken G3SDW Moderator

    Cannot open the images but for sure it is VDSL in its learning stages.

    As long as the owner of the system does not keep turning it off, which i think is why it went away and came back again, then it will disappear on its own.
  10. Pete Steadman

    Pete Steadman New Member

    Thank you for your help Ken. Fingers crossed they'll stay away from that power button. Hoping they're not eco nuts!! If I could find them, I'll ask to build them a solar panel for their modem.... wait a min, whats this new interference. lol have a great weekend Ken :D
  11. Ken G3SDW

    Ken G3SDW Moderator

    OK Pete, see if you can find out if anyone close to you has recently had a new system installed.

    As for Solar then as long as it is installed correctly with well dressed cables and to the correct standards then there will not be a problem on HF

    Good week end your self.
    Pete Steadman likes this.
  12. Pete Steadman

    Pete Steadman New Member

    one more quick question. would my assumptions be correct in thinking: due to being able to hear these carriers. Is my station likely to have a higher than normal noise floor, drowning out weak signals on some bands due to VDSL garbage?
  13. Ken G3SDW

    Ken G3SDW Moderator

    Not necessarily so Pete, the biggest VDSL problem is 1. overhead drop wires with poor joints in the distribution box, like the one at the top of that pole, and 2.multiple extensions to the land line in the house which in both cases put the system in an unbalanced state.

    New up to date face plates are normally installed with a new installation but if self install is done then old out of date and maybe faulty ones can sometimes be responsible for excess noise.
  14. Ken G3SDW

    Ken G3SDW Moderator

  15. Pete Steadman

    Pete Steadman New Member

    Few, that's a relief! I'm going to have to look in to this more. fascinating subject!

    Cheers Ken
    73's
  16. Ken G3SDW

    Ken G3SDW Moderator

    Enjoy the hobby Pete just like i have for the last 56 years, i am always hear at all times to help if ever you have a problem.
  17. Pete Steadman

    Pete Steadman New Member

    oh it's VDSL, I recognise the distinctive shape of the guard bands (contained within the EMC leaflet) from my spectrum analyser screen. I was thinking that it was caused by antenna gain or front end filtering within my SDR. that's that mystery solved. off to see if playing with the earth can improve it.

    to digress a little, I hate when ham radio is referred to as a hobby. It seems to trivialise it like a collection of tea pots. The way it envelops you, its more like a chosen way of life or a chosen path of education. I know its an activity, but you wouldn't call veganism a hobby lol.

    Thanks again Ken, top bloke!
    73
  18. Ken G3SDW

    Ken G3SDW Moderator

    I must agree with your completely Pete, yes not like a hobby, more of a way of life, it has been for me since i was 12 years old, licence at 16 and now a ripe old 72 but still think as i did when i was 12 lol

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