DCC causing broadband interference

[gilbo2]

I have noticed that even without any locos physically on my layout, that my DCC system (using eLink) causes interefernce on my broadband, shown by high CRC errors as below when it was powered up from around 19:30 to 23:00.

I have checked all wiring and all seems good.

I suspect it has allways been like this its just I have only now started to monitor the broadband.

Does anyone know of any supression that can be fitted without killing the DCC signals?

/media/tinymce_upload/a6ab665e22f4a913bbd6b9d260c827c0.png

[Chrissaf]

You could try fitting a snubber RC filter, even if it doesn't fix your BB errors. Your DCC signal quality will benefit from it. The 100 Ohm resistor will get very warm if you use a 1/2W rating. I recommend using at least a 1W rated resistor and ideally a 2W one. My 2W resistors only get warm to the touch as opposed to getting hot enough to take the skin off one's fingers. The 0.1uF capacitor is of the ceramic disc type and should be rated at 50V AC or better.

/media/tinymce_upload/171d4a9e829f4ef963e9119376f160f6.jpg

Image pasted from a previous reply.

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PS - Have you done the same BB monitoring test but WITHOUT firing up your DCC layout. The reason I ask, is because 19:30 to 23:00 is the peak BB usage period of the day and BB data errors can be expected to rise during this time period normally. I would be more convinced if you did exactly the same test again, but this time you turned off your DCC between say 21:00 and 22:00 and your graph showed a corresponding dip for that time period.

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Also, since you stated eLink. Then this means a PC is involved. If it is a Laptop (not running on batteries) then there will be a 'Switch Mode Power Supply'. These power supplies can also be a source of radio frequency noise. So also do your test with the eLink powered but without the PC powered up.

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In other words, don't just assume that it is the DCC data signal on the track that is causing your BB errors.

 

[96RAF]

Hi

As well as your CRC errors have you got the associated SNRMargin graph.

 

Does this trend also show if you have the track loaded with locos, they don’t need to be running, merely on track.

 

There are other things you can check like swap out the ADSL filters if they are not built into your wall socket and maybe run a QL test.

 

In addition is this an isolated event purely when DCC is live or is it a time of day event and what other kit do you have in the house that could maybe cause it, like a central heating pump or fridge/freezer, etc running coincidentally with the DCC.

 

Any and all info will help no matter how vague.

 

I will download the app onto my main and train PCs and see how it affects my broadband when DCC is on and if both PCs show the same errors at the same time. I can also monitor stuff using a scope if necessary.

 

Rob

[Triumph Owner]

How are you connecting to your Broadband? WiFi or Cat5 cable?

 

Paul

[2e0dtoeric]

Also - how are you spreading the broadband around the house? If you are using those wall-wart PLT things that BT supply, using the house wiring instead of running cat5, they also radiate masses of radio noise. They have been proved to slow down telephone line broadband by increasing the error noise, wipe out DAB radio, HF broadcast radio, and up to and includng Air Traffic radio!

As Chrissaf put, a lot of wall-wart power supplies have been built being VERY economical on the suppression components (ie for but not with!), and all kinds of domestic equipment uses them, from your computer, to your electric toothbrush!

It doesn't even have to be in your house, but any one of your neighbours on the same phase of the main power supply could be the culprit.

Plasma tv's also are terrible for radiated noise, and as the screen ages, they get noisier.

Next time you see this interference, go around, turning one thing off at a time, until you can isolate it at source.

[96RAF]

The simplest check I can think of is to tune a cheap transistor radio to 612kHz AM and move it around the house. As you near a source of REIN or SHINE you will hear the radio protest. Use this as a guide as to what may be causing your dropout event. You often find it is not the ‘box’ that is the root cause but the power supply, especially cheap replacement wall wart PSUs With inferior components as inferred earlier.

Anything electrical in your house or as stated your neighbours houses could be a noise generator enough to ‘kill‘ your BB connection. Maybe the dropout coincides with your neighbour doing the washing or running on their treadmill.

Rob

[gilbo2]

Thank you @Chrissaf, I will give the snubber circuit a try.

 

Yes, I have tried having DCC powered up at diferent times during the day which aligns exactly with the rise in BB errors. I have even tried applying a short circuit to the rails to "switch off" elink and this will cause the errors to disappear until elink powers the rails back up again.

[gilbo2]

Sorry, forgot the quirks of the forum to not quote the message replying to :-(

 

@RAF96 below is the SNRM plot for the duration when DCC was powered up. There is a slight drop aligned to the period 19:30 to 23:00 when I was using the layout. The BB errors do not change higher or lower if locos are running or stationary, not that I can measure anyway.

/media/tinymce_upload/89355c4a4963eb8af92fafa96d0c8b6c.png

 

I have done the quiet line test on 17070 and thats good, nothing at all. I will try another ADSL filter though, currently its the type built into the BT socket.

 

I can guarantee its when my DCC track is powered up the errors occur. I have tried a number of times switching it on and off for a few minutes and it then mirrors onto the error plots. During these times I only disconnect elink, all the power supplies, lights etc remain on.

[gilbo2]

@RAF96, I have just replied to your post, thanks. I attached the SNRM chart so its gone off for moderation again :-(

 

During the time when DCC is on, there is a slight SNRM drop but my post, when it appears, contains more feedback.

[gilbo2]

@triumph Owner, thanks for the reply. My home network is a combination of both wi-fi and ethernet cable connections. The errors though are before this stage unless noise is getting picked up through the ethernet cables and finding there way onto the DSL side?

[gilbo2]

@2e0dtoeric, thanks also. My router is connected to the BT master socket and there are no other extensions or phone sockets in our property, so the phone line wiring itsself is quite short and straight forward, from my side at least.

 

I can "stop" the BB errors simply by disconnecting the elink track output, eg by a short circuit. I could post a plot when I do this a couple of times and you would see what I mean, but that would mean another image for moderation :-)

[2e0dtoeric]

Dgilbert - please do NOT use the blue button with the arrow, it is not a reply button, but repeats all the previous post.

Scroll down to the empty white box, type there, and use the GREEN button with 'reply' in it.

Everyone falls into that trap!

[gilbo2]

@2e0dtoeric, apologies its been sometime now since I'd replied to a post and forgot to use the green button. All subsequent posts remembered though  😀

[Chrissaf]

I'm impressed.......you certainly seem to be right up to speed in understanding the technicalities of BB and understanding the meaning of the graphs your monitoring software is generating.....you are the first person I have ever come across who was aware of the 17070 quiet line test........now if I could get my hands on a BT engineers 17070 access code then I could access more tests than just the quiet line one.

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For other's who are interested and have BT provided PSTN lines. Dialling 17070 from your phone gives you access to an automated line tester. However to access the in-depth testing you have to input a BT engineers code. The quiet line test allows you to listen to the line for any noise that might be affecting your BB speed. Other tests you can perform without the engineers access code is 'Ring Back' test and 'What is my number'. TIP: use a corded phone for the quiet line test, a wireless DECT phone will generate its own noise and gives a false impression about the actual line silence.

[gilbo2]

@Chrissaf, thank you for your comment  😀

 

I have learnt over the years what the graphs are reporting and its very rare to pin-point, as in this case ,the route cause.

 

The problem now is, how (and if) I can fix this. I have tried the snubber circuit this morning but there is no measurable difference to the BB errors. I then realised when I did this, that when a first wired up the layout a number of years ago, I had fitted "snubbers" to the ends of my system. I just tried one at the beginning for good measure as per your diagram, but no success.

 

I guess the trouble is that all the work we put into the DCC ring bus and all the rails themselves are making a really good antenna. Do you or anyone else have another suggestions to try please?

[Triumph Owner]

A big drastic step, but do you have access to another provider that does not use the BT lines? I have never been a fan of ADSL, which basically uses a quirk of physics to allow two different signals to travel in the same cable.

 

Paul

[gilbo2]

@triumph Owner, yes, I could go cable with VM but stuck into a contract at the moment and they are quite a bit more expensive.

 

This issue here does not really impact my BB service, it just causes "interleave" to kick in which drops my line speed by around 5 Mbps to correct the errors. I know some people get very paranoid about "chasing" BB speed numbers and I'm not into that game, I just want to try and fix something that I know where the issue is coming from.

[96RAF]

Thanks for the extra feedback dg2.

 

Re your line filter - if it is built into the socket adding a dongle type may screw things up so I wouldn't bother adding one.

 

I have been busy this morning on Cyprus admin tasks, etc - thus didn't get round to carrying out my own testing yet, but I think the end game will be a noisy eLink power supply unit, especially if its the 1-amp wall wart variety. I have two 4-amps and a couple of 1-amp units I can listen to this afternoon. Probably nothnig much you can do about it if this is the rogue, except selective choice of units. It may be the 4-amp unit is quieter. If it is a noisy eLink then Hornby may have to look at an EMC fix.

 

I'll be back in around 3 - 4 hours.

Rob

 

Rob

[2e0dtoeric]

If you suspect that your BUS is acting as an antenna, what you could do, if you have the equipment to hand, or can borrow it from a local (to you) radio ham, is work out what the resonant frequency of the BUS is, with the controller-end of the feed wire disconnected, and make an open-circuit choke for it (a measured quarter-wave length of coax cable with the inner soldered to one side of the bus, and the outer to the other side), and leave the far end open-circuit.

That will stop the accidental antenna from working on that frequency. I don't think that would affect the DCC data.

(edit to add a comment)

[96RAF]

We have had a serious thunderstorm induced power outage all afternoon and evening so I  achieved absolutely nothing in the way of testing. Maybe tomorrow, but it looks like things are progressing on the forum by way of further suggestions, whilst I was dark.

Rob

[gilbo2]

@RAF96, thank you for looking at the testing from your side as any help on this is appreciated. Sorry about the storm!

[Chrissaf]

Was this the storm now to the North East of you.

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/media/tinymce_upload/d408ae4bf931fe329104950ab268e5d4.jpg

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Image taken from this website showing world wide global lighting strikes in real time.

https://www.lightningmaps.org

[96RAF]

Could well have been Chris. When we get them they are usually nasty and prone to taking home electrics out. We seem to be more fortunate in that we have our own sub-station. So far in nearly ten years I have not lost any kit, apart from isolated and unrelated failures like wallwart PSUs or powerline adapters. Maybe the 3-phase supply is more tolerant of power surges. Normally ts the local,power station falling over. Its never been right after the local Navy Base munitions explosion killed it a few years back.

Rob

[96RAF]

I have downloaded DSLStats app onto both my main PC which is wired to the router and also to my Train-PC which connects to the internet via a Powerline adaptor into the ring main.

 

My ZTE ZXDSL932v11 router is listed in the app as requiring special login and it will start recording but so far the graphs and stats on both PCs are showing absolutely no line activity after a couple of hours even with the graph Y Axis on autoscale.

 

The AM radio test on around 612kHz however is a different story - there is an audible increase in 'shshsh' noise when the train controllers (Elite, Select W/About and eLink) are switched on and when a Select with a 1-amp PSU is located near the radio the noise is extremely loud, thus proving definitely that 'noise' is being generated by the train kit.

 

Whether this is having any real effect on my broadband connection and quality I cannot tell as the only stats I can generate are from the router homepage as below. After several page refreshes since start of this test the numbers in the screen grab below have not changed and these are obviously fairly meaningless as they are cummulative from last router reset and not zeroable from my chair.

 

I don't know what else I can do to help as the DSLStats app although having accepted my router type and settings is apparently recording but not producing any meaningful data, not even connection speeds.

 

/media/tinymce_upload/d9ce65ae1cbfa0912721269af3680fa0.png

Rob

[2e0dtoeric]

AARGH! Powerline adaptors are PLT = radio transmitters! THEY could be causing the noise!

https://www.ban-plt.org.uk/