[Not] Living with 6m/50MHz interference!

s6 wide-band hash (Christmas 2010)

December 2010: It's a funny thing noise. Well, it is for me anyway. You hear a noise and think that it's just started, however, in most instances it's actually been there for many months but you have only just registered it.

In this instance I was undertaking some EME activity and turned the antenna to 240 degrees and there it was - an s6 hash wiping out everything in that direction. Surely I would have noticed this before I asked myself?

Maybe I did, maybe I didn't, but here it was anyway.

There is only one house close to me on that alignment and it is just over the road. I have come to the conclusion that most cases of interference originate from quite close. I took my trusty FY-847 and HB9CV antenna across the road and walked up and down outside for a couple of minutes (in the dark I might say!.

Yes, it was clear, the noise definitely originated in that house.

I knew the family quite well as 20 years ago I rebuilt their TV antenna and added a mast head preamp that would not overload. Why did I do this? Well, I was wiping their TV picture out - indeed I even wrote about it then!

This problem has exactly the same noise characteristics as occurred with another neighbour and described here. I suspect it's another 'rogue' television.

Tomorrow I will knock on the door and find out!

Which I did and arranged to go back the next day with my loop and 847 and try to find the offending equipment.

These are the steps I had to follow with my wife listening to noise and telling whether the noise disappeared at any point.

  1. I thought is was the main TV so we turned it off - no change!
  2. We turned off ALL the audio equipment in the downstairs rooms by unplugging all the power plugs - no change!
  3. We went into the other downstairs living rooms and unplugged all the audio and TV equipment in that room - no change!
  4. We unplugged all the equipment in the kitchen - no change!
  5. There was no other electrical equipment downstairs so it must be the computers upstairs! The owner went upstairs and unplugged all the computer equipment and peripherals  - no change!
  6. So, I was confused as surely the noise should have disappeared by now but it hadn't?
  7. I asked whether I could turn all the electricity in the house off at the switch box? The owner agreed. Wow, the noise disappeared according to my wife in the shack!
  8. We put the power back on and the noise reappeared so we went round the whole house pulling out all the power plugs in each room  - the noise was still there!
  9. So what was causing the problem? Not the security alarm - not the boiler! All that was left in the house were bed-side alarms and bed-side lamps in two of the bedrooms so they were unplugged. By this time I had already disconnected with my wife on the mobile phone as I thought. I went back to my house only to find the noise had disappeared! Confusion reigns!
  10. Tearing my hair out I went back to the house suspecting the two bedside lamps or clocks.
  11. We plugged those back in and there was still no noise - everything in the house was now turned on again but there was no noise!


It looks like the problem turned out to be an arcing mains plug - it could be that the plug was not properly pushed into the socket. It might have corrected itself in time if someone touched it, however it might not, and the noise would have continued for days or weeks. Anyway, it's gone for the time being and that is all that matters! If it reoccurs I know where to go.

Wrong, wrong, wrong!

I was wrong. The noise came back the next day.

I went back to house and went upstairs to the mains socket that I thought was causing the problem and started pulling out plugs. The last plug was connected to a laptop and as soon as I unplugged this the hash disappeared. The owner's brother had brought home a Toshiba laptop from work and had unplugged it while I doing my investigation yesterday. It was the 65W 19V AC adapter which of course is a switching PSU. I have ordered a replacement from Ebay so I hope that this particular problem has bee put to bed! The offending PSU can be seen in the picture on the right.

The lesson? Do not let people unplug items while you are not there to see the effect!

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