Amateur Radio - HF Interference

[G7CNF]

BT is recalling ALL the PLT adapters they supplied made by Comtrend, citing a safety issue. The recall appeared only three days after the ITU Recommendation on PLT interference maximum levels... The adapters BT are using to replace them hide the pollution until the adapters are used, Lee Talbot of BT Vision Complaints wrote, "While customers are watching video-on-demand services the adaptors will be in normal power mode and emissions will be the same as the earlier models of Comtrend adaptor."

[battlestarone]

you have everything in there,plt,power line noise,and plasma noise...best of luck

[WinterWeatherII]

power line adapters should be outlawed

[SmashlytheBassGod]

Hi,

I would like to sample a part of this for an introduction to a song I'm working on. Would this be ok?

Ta,

Smashley

[MrJoshuaUK]

Hey,

Of course - Make sure you send me a copy when it's done please, I'd love to hear what it sounds like!

Cheers

Josh

[superarticulation]

@SmashlytheBassGod Good point!

[trifidsagitarius]

@SmashlytheBassGod

LOL Exactly what I was thinking. At one point I thought I was listening to the beginning of the WHO's Baba O'Riley.

[MrJoshuaUK]

Oh and as an update to my previous posts, I replaced my neighbour's Switch Mode Power Supply (for her TFT monitor) and have had no problems since.

[knikk77]

is there a cellular mast around there, it sounds very much like cellphone base antenna. Or a wireless phone base station.

[scidept]

I would like to burn this to a DVD for use within our KS4 science lessons - communication systems and interference - Can I have your permission? Chris - Sci Tech

GD7ELF

[MrJoshuaUK]

Hi Chris - No problem at all. In fact, instead of upscaling a mushy YouTube video to DVD, I could do you a proper copy on DVD with a better explanation of what's happening if you'd like? Email me "josh at tigerstyle . co . uk" if you're interested? Cheers - Josh

[mikesndbs]

Hello, I would like to use part of your video and sound track in a update to the UKQRM video.

Would this be ok please?

Mike UKQRM

[MrJoshuaUK]

Hi Mike

No problem, if it helps other people out!

Cheers

Josh

[MrJoshuaUK]

(continued)... I spoke to my neighbour and gave her the HT and asked her to walk around her house with it, watching the meter to see where the noise was strongest. It turned out to be her 17" TFT monitor on her computer. I was invited in and the monitor has a cheap Chinese SMPC (12V 4.16A). Turn the monitor off and the noise totally goes away! So, I'm either going to buy a new power supply for the monitor (hopefully better filtered) or buy her a decent 2nd hand monitor!

[MrJoshuaUK]

WOOOOHOOOO! Well, tonight, the neighbour with the BT Vision Power-Line Adapters told me he was going to get rid of the BT Vision system because he wasn't using it much. He unplugged the adapters and the digital noise went straight away. I then concentrated on the power type noise. I turned our power off at the breaker, then walked around the neighbourhood with my Kenwood TH-F7 tuned to 17MHz AM (on the internal bar antenna) and found the signal strongest at my immediate neighbour's house...

[MrJoshuaUK]

Hi, it's an Icom IC-7000... It's a lovely radio, you'd be very happy with one (so long as you don't have local QRM!! :)

[jiggawoo]

what model radio is that ?

its really nice id like to get one :P

[jeffpicks]

Does it disappear when it rains ? If so, suspect the powerlines as stated in earlier comments.

Or, maybe it's aliens trying to have a QSO ?

[MrJoshuaUK]

I've kind of given up with it recently but I'll check next time it rains. Thank you!

[countryeugene]

There can be many sources:

- switching supplies - PCs, TV and even cell phone chargers - some cheap supplies don't have filters;

- brush motors that produce big sparks;

- DSL modems - low quality cables, bad twisted/shielded;

- home automation and alarm systems that use the power system for data transmission.

In some points it sounds more like data transmission than switching supply or motor.

[MrJoshuaUK]

Hi, Thanks for the comments - The noise above 16MHz has been proven to be caused by some BT Vision powerline ethernet adapters - This noise is obviously data transmission as you mentioned. I think the noise below 16MHz does sound more like arching or some other sort of electrical "noise".

[Proghartedo]

Look for arcing powerline insulators. Go out at night and look at the power poles and you will hear and maybe even see one arcing. Thats what it sounds like to me. And of course, a bad door bell transformer, or recently installed electric fence could do it as well.

[MrJoshuaUK]

I do have some power lines behind the house, about 100m away, but they are just lines on wooden poles rather than big pylons. I'll have to go for a walk one night to see if I can spot any arching. Thanks!

[theBTman]

Contact OFCOM. Interference should nto be tolerated, neither does it have to be.

[MrJoshuaUK]

Hi, I did contact OFCOM and they told me to get my neighbour with the BT Vision Powerline adapters to sort those out before they'd look at the noise below 16MHz (as we'd proven that the noise above 16MHz was caused by these devices). Just a shame my neighbour isn't helping out by contacting BT to get them swapped out :(

[g0tmx]

The QRM below 16Mhz sounds very much like a switched mode PSU somewhere close by. I experienced the same thing. A SM/PSU was powering my PCR2500.. cheap nasty little power supply which when replaced with a better one totally eliminated the interference. If not in your house, perhaps a near neighbour is using one?

[MrJoshuaUK]

I think the problem is that if the lower frequency noise IS a switch mode power supply, it'll be very hard to find which one of my neighbours is causing the issue as there must be a LOT of these power supplies on my street! But thank you for your comments :)