Interference identification?

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DanubeBCL
Posts: 160
Joined: Sat Jul 02, 2016 12:39 pm

Re: Interference identification?

Postby DanubeBCL » Sun Mar 12, 2017 12:15 pm

CaptainNemo wrote:If I understand well, jpsa posted an image of an idle modem,
I am not yet sure. That depends on the distance to your neighbour, the infrastructure in his house (wire resonances and line attenuation, distance between his two PLC-wallplugs a.s.o).

For me it is a modem in normal operation being a bit further away. Idle modems do indeed a sort of "ping" periodically. These pings of my neighbours (if I can discriminate them, when they are all on I have no chance in that mess to discriminate single modems) take place irregularly appr. every 1 or 2 seconds. This sounds like a short lightning stroke. This alone is very nasty.

I have found an older image from my WiNRADiO G33DDC of my neighbour's PLC (40 m away) and an image from a friend wo had even more trouble (Perseus screenshot). In his case the modems were only 7 m away from his antenna. Looking at my image you can see that only the strongest radio stations in the 49 m band come through. I have marked the notches green. Considering that the noisefloor here in the ham bands is about -125 to -130 dBm and the PLC noise is up to -100 dBm you can imagine that this is a big problem. (On higher frequencies there is even more noise!)

In the meantime I have given up making screenshots and recordings: It is all useless! I hate to deal with the subject and switch off the receivers when I am nerved, you understand.

There is an article of a German magazine, unfortunately in German, but in some images taken from an Elad receiver you can see what PLC means in real life (pages 2 and 3). Maybe google translate can bring a bit clearing when you are interested in the details. https://www.teltarif.de/powerline-devol ... 59169.html
Especially this image: https://www.teltarif.de/arch/2015/kw13/ ... est-6l.jpg You see the ham band notch and left and right the PLC mess.

73, Heinrich
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CaptainNemo
Posts: 114
Joined: Mon Jan 05, 2015 1:22 pm
Location: Genoa - Italy

Re: Interference identification?

Postby CaptainNemo » Sun Mar 12, 2017 12:41 pm

Thank you very much.

It seems that I have this sort of noise but fortunately it is not so strong.
That's probably the reason I never realized this was caused by a powerline modem. I just archived that as due to thunderstorm around.

In fact I have more noise from other "local" sources: lcd/plasma television set for example and the elevator's inverter (I live in a block).

Thank you all: another bit of knowledge has come.

Bye
Gio

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DanubeBCL
Posts: 160
Joined: Sat Jul 02, 2016 12:39 pm

Re: Interference identification?

Postby DanubeBCL » Sun Mar 12, 2017 12:47 pm

Yes, PLC is the biggest jammer, but there are more: Switched power supplies, monitors, lcd and plasma tellies, lawn mowing robots, photovoltaic inverters, LED bulbs, "smart" (?) homes, VDSL spectrums, electric pasture fences, even welding devices in car service stations ... The chain is too long for enumeration.
Difficult to fight them as the law is mostly on their side (missing or very generous electromagnetic compliance handling).
73, Heinrich

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CaptainNemo
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Location: Genoa - Italy

Re: Interference identification?

Postby CaptainNemo » Sun Mar 12, 2017 2:47 pm

Could it be a PLC/PLT modem?

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DanubeBCL
Posts: 160
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Re: Interference identification?

Postby DanubeBCL » Sun Mar 12, 2017 4:03 pm

CaptainNemo wrote:Could it be a PLC/PLT modem?
The ham notch of the 20 m band should be seen a bit clearer. And the waterfall lines should be interrupted rhythmically (unless the modem is in full streaming mode). See jpsa's examples! It could be, but then it is fortunately a weaker, more distance one.
Have a look at other ham bands. Often the higher frequencies show more PLC/PLT interference because the length of the powerline wires in the houses better matches these frequencies and they radiate more energy. Often, but of course not always. Depends on the infrastructure of the house.
73, Heinrich

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PG3
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Joined: Mon Nov 14, 2016 6:04 am

Re: Interference identification?

Postby PG3 » Mon Mar 13, 2017 6:14 am

Are these PLC modems susceptible to any kind of interference that would make them inoperative?

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DanubeBCL
Posts: 160
Joined: Sat Jul 02, 2016 12:39 pm

Re: Interference identification?

Postby DanubeBCL » Mon Mar 13, 2017 8:32 am

PG3 wrote:Are these PLC modems susceptible to any kind of interference that would make them inoperative?
Partly. Transmitting with appr. 100...300 W on a ham band in the vicinity (appr. 20 m) of such PLC makes them inoperative. But they are very insensitive. They work with signals af around 175 mV and you have to infiltrate high levels of energy into the power lines of your neighbour to block them. They also have technologies to avoid single carriers and you should work with high level broadband noise from 1.6 to 68 MHz to interfere. There are fairytales on the web saying you can block them with noise from "choppers" (like old doorbells) producing sparks. But according to my experience this only works when the PLC is in your own house. Normally the jammers are appr. 200...300 m away from your house and it is difficult to inject enough energy even from a ham transmitter with appr. 750 W.

Then there is another problem:
When you transmit you block your own receiver and you cannot hear the radio stations you would like to hear. As soon as you stop transmitting the PLCs resume operation. The neighbour normally is not so clever to understand that his PLCs are the culprit. He simply waits until the internet is back and does his internet shopping an hour later. You would have to transmit 24/7 to make him think.
I know what I am talking about. I tried to block the PLC of my neighbour by transmitting on the ham bands. He simply kept his PLC running and did not change the technology. As soon as I stopped transmission his PLC came back and I again could not listen to the radio. Every effort of mine was in vain. And, as I said, you cannot block the deaf dumb PLC which is 300 m away. But it can block weaks signals on your sensitive SW receiver. I have evidence that I disabled the PLC of my western neighbour (20 m from my TX antenna) with 300 W. (His wife once slipped on the tongue at the garden fence complaining about internet problems.) But I also have evidence that I could not interfere the PLC of the neighbour in the Southeast 35 m away. Interfering PLC is not as easy as some web pages make believe.
73, Heinrich

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PG3
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Re: Interference identification?

Postby PG3 » Mon Mar 13, 2017 9:09 am

Might be time to construct a monster Tesla Coil :P

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DanubeBCL
Posts: 160
Joined: Sat Jul 02, 2016 12:39 pm

Re: Interference identification?

Postby DanubeBCL » Mon Mar 13, 2017 9:58 am

Might be time that some rich man/woman complains at the Eropean court of human rights because of offending free access to broadcast listening and media.
But even the German amateur radio club could not do anything against the latest German law about electromagnetic compliance from September 2016 which practically frees the national spectrum supervisors from pursuing interferences in broadcast and(!) ham radio reception. Main argument of the parliament: The number of reported radio interferences has drastically decreased over the last years. It is not appropriate to maintain the stuff on a level as in the past. On the contrary: The personnel is reduced.
Two petitions (I am aware of) to the European Parliament against PLC (which only appr. 8000 people signed Europe wide) failed (of course). I myself practised my right as citizen of the European Community and appealed to the Parliament as an individual. But I knew that this effort was ridiculous, of course.
73, Heinrich

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13dka
Posts: 125
Joined: Sun Feb 14, 2016 8:40 am

Re: Interference identification?

Postby 13dka » Mon Mar 13, 2017 7:54 pm

Well this thread must be jinxed...I enjoyed mostly unharmed reception until this weekend but now... :(

...exact 1 second pulses from 0 to 10 MHz and some dense muck between 2 and 3 MHz...

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...level-wise centered at 5 MHz (check the faint peak hold line on the spectrum to see how loud the pulses are)...

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... and it looks like it's on 24/7. Doesn"t look like PLC but the name of the animal doesn't mean anything. The only thing I care about is "will it go away?". Like I wrote before, it's a dangerous time to invest serious amounts of money into ham radio or SWLing.

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