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Forums › New Zealand Broadband › How to reduce TV interference with DSL


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Master Geek
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Topic # 201372 16-Aug-2016 00:04
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Hi,

 

 

 

Everytime i turn my TV on (plasma), my VDSL sync speed drops about 20% to maintain a 9db SNR margin.  When i turn the TV off, speed stays down and margin rises to 11.

 

Are there any defences commonly employed? wrapping the modem in tinfoil?  Would a run of twisted pair instead of regular phone cable be immune?

 

Dan.

 

 

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  Reply # 1612257 16-Aug-2016 00:04
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Hello... Our robot found some keywords in your post, so here is an automated reply with some important things to note regarding broadband speeds.

 

If you are posting regarding DSL speeds please check that

 

  • you have reset your modem and router 
  • your PC (or other PCs in your LAN) is not downloading large files when you are testing - you are not being throttled by your ISP due to going over the monthly cap 
  • your tests are always done on an ethernet connection to the router - do not use wireless for testing 
  • you read this topic and follow the instructions there.

Make sure you provide information for other users to help you. If you have not already done it, please EDIT your post and add this now:

 

  • Your ISP and plan 
  • Type of connection (ADSL, ADSL2, VDSL) 
  • Your modem DSL stats (do not worry about posting Speedtest, we need sync rate, attenuation and noise margin) 
  • Your general location (or street) 
  • If you are rural or urban 
  • If you know your connection is to an exchange, cabinet or conklin 
  • If your connection is to a ULL or wholesale service 
  • If you have done an isolation test as per the link above 

Most of the problems with speed are likely to be related to internal wiring issues. Read this discussion to find out more about this. Your ISP is not intentionally slowing you down today (unless you are on a managed plan). Also if this is the school holidays it's likely you will notice slower than usual speed due to more users online.

 

A master splitter is required for VDSL2 and in most cases will improve speeds on DSL connections. Regular disconnections can be a monitored alarm or a set top box trying to connect. If there's an alarm connected to your line even if you don't have an alarm contract it may still try to connect so it's worth checking.

 

I recommend you read these two blog posts:

 




I am the Geekzone Robot and I am here to help. I am from the Internet. I do not interact. Do not expect other replies from me.

Mr Snotty
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  Reply # 1612272 16-Aug-2016 01:28
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Wow your Plasma must be spewing out RF interference for that to happen. Replace the plasma? ;)

 

Jokes aside move your router away from your plasma (assuming that is its location) to a more suitable spot without interference might be the best idea.




Michael Murphy | https://murfy.nz
A quick guide to picking the right ISP | The Router Guide | Community UniFi Cloud Controller | Ubiquiti Edgerouter Tutorial

 
 
 
 




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Master Geek
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  Reply # 1612311 16-Aug-2016 08:41
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Problem with moving it is it's in the middle of the house, so if i move it to the other side of the house, then the WiFi reception wont be so great in the lounge.  It's already on the other side of the room to the TV.  I'm gonna move it a couple more meters into the next room and see if that makes a difference.  But if it's actually the telephone wires in the wall etc picking up the signal then i guess that wont make a difference?

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  Reply # 1612317 16-Aug-2016 08:55
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if its already a few meters from the TV I think its time to get a new TV

Mr Snotty
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  Reply # 1612443 16-Aug-2016 13:04
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If the telephone cables are in the wall by the TV then doing the following could help:

 

1) Ensuring you've got a master filter installed.
2) Replacing the cable from the standard cat4 untwisted to something a bit better like cat5e shielded.




Michael Murphy | https://murfy.nz
A quick guide to picking the right ISP | The Router Guide | Community UniFi Cloud Controller | Ubiquiti Edgerouter Tutorial

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  Reply # 1612444 16-Aug-2016 13:10
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PeterReader: "Ensure you've got a master filter installed."

 

 

 

One can see a standard response coming whenever the characters DSL are in an email.




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  Reply # 1612828 16-Aug-2016 21:31
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Try wrapping the phone cable around a ferrite near the modem.

 

Image result for ferrite dsl

 

 

 

If you can get your hands on a few I'd experiment also with router and TV power leads etc.

 

 

 

 

Image result for ferrite dsl

 

 

 

Image result for ferrite dsl

 

http://www.jaycar.co.nz/u15-ferrite-voltage-spike-protectors-noise-suppressors-pk-2/p/LF1294

 

http://www.jaycar.co.nz/l15-35x21x13mm-toroid-or-ring-cores-pk-2/p/LO1238

 

 

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  Reply # 1612953 17-Aug-2016 07:48
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I would have thought adding a ferrite core would have quite the opposite affect, attenuating any RF through given cable allowing DC to pass and resulting in a slower sync speed?

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  Reply # 1612960 17-Aug-2016 07:54
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They attenuate common mode signals, anything that is going both ways thru it like a ballanced phone or network signal will be uneffected. The common mode crap will couple across into other parts of the circuit once inside it.

 

Those ferrites are really common on cables for things to help them pass emissions testing, but they work both ways.




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  Reply # 1617084 24-Aug-2016 22:49
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dantheperson:

 

Hi,

 

 

 

Everytime i turn my TV on (plasma), my VDSL sync speed drops about 20% to maintain a 9db SNR margin.  When i turn the TV off, speed stays down and margin rises to 11.

 

Are there any defences commonly employed? wrapping the modem in tinfoil?  Would a run of twisted pair instead of regular phone cable be immune?

 

Dan.

 

 

I think ADSL is sensitive to HF radio frequencies, but the modem is probably not the problem. Twisted pair from the building entry point to the DSL jack would help if you also put in a master filter at the entry point. The filter blocks interferance on the untwisted wires from being fed though to the dedicated (and twisted) DSL wire. The existing cable might be running through the wall directly behind the TV...




Qualified in business, certified in fibre, stuck in copper, have to keep going  ^_^



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  Reply # 1617107 24-Aug-2016 23:55
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yeah DSL signal is in the same range.  Trick i found is to tune an AM radio to about 600kHz and walk around with it turning things on and off. Looks like 600kHz is about the middle of the ADSL2 frequency range.  TV makes massive noise for quite a distance.  WiFi router also puts out allot of noise but at quite short range, i.e. you can't pick it up more than a meter away, though the router is normally right next to it.

 

Gonna try and pickup some of those ferite coil things from Jaycar on the weekend.  The stock TV power cable already has a pretty big one on it.

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  Reply # 1617112 25-Aug-2016 00:57
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Another possibility, the TV has a faulty power supply. Meaning the RF interference is getting back fed out of it's power cable. If so then every single mains cable in your house will be spewing out RF interference whenever the TV is on.

 

 

 

Would still recommend a master filter. And relocate the VDSL modem as close as possible to where the phone cable enters your house. And get a proper Wifi AP as well. Then you can put each device in the best locations for their operation. Instead of having to compromise.





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  Reply # 1625201 7-Sep-2016 17:22
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dantheperson:

 

Gonna try and pickup some of those ferite coil things from Jaycar on the weekend.  The stock TV power cable already has a pretty big one on it.

 

 

How'd you get on with this? I'm interested to know as there's varying reports of success online.



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Master Geek
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  Reply # 1625285 7-Sep-2016 21:55
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solutionz:

 

How'd you get on with this? I'm interested to know as there's varying reports of success online.

 

 

I didn't manage to make it to JayCar the other weekend so haven't tried the magnets yet.  I did unplug all the cords except for the powercord (which has a built in magnet) and it didn't make a difference.  Wondered if the HDMI and Audio cables might have been acting as transmitters.  I moved the modem into the next room, only about 3 meters further away, but it's made a significant improvement.  As part of the move i also moved the phone socket into the next room, so that't's also 3-4 meters of phone cord along the skirting board that is further away and picking up less interference.

 

There is another socket in the next room on the other side to the modem. That's less than a meter away, probably worth disconnecting that one.... no wait that's one of the ones that's on the half of the wiring behind a 'master' filter, so should be ok?

 

So anyways SNR now hovers around 7-8 when the TV is on. Some days it even hits 6 for half a minute, but it's not enough to force it to retrain at a slower sync speed. Before the rearrangement it would retrain within a minute of turning the TV on.  When TV is off, SNR jumps back up to 10.  Stays pretty constant on 10, though last night it did have some very brief jumps to higher SNRs.  These logs show when any stats change.

 


Sep 6 21:09:45 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 6 21:10:13 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=10 Atten=26 ] <-- TV off
Sep 6 23:42:59 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=10 Atten=26 ]
Sep 6 23:43:26 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=14 Atten=26 ]
Sep 6 23:43:53 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=13 Atten=26 ]
Sep 6 23:44:21 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=10 Atten=26 ]
Sep 7 01:21:04 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=14 Atten=26 ]
Sep 7 01:21:31 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=10 Atten=26 ]
Sep 7 09:32:51 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=11 Atten=26 ]
Sep 7 09:33:18 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=10 Atten=26 ]
Sep 7 18:50:10 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ] <-- TV On
Sep 7 18:50:37 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 18:55:08 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 18:55:35 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 18:56:02 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 18:58:45 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 18:59:12 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 18:59:39 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 19:00:06 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 19:01:28 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 19:02:49 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 19:03:16 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 19:04:38 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 19:05:05 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 19:06:26 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 19:06:53 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 19:07:20 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 19:07:47 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 19:08:15 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 19:08:42 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 19:11:24 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 19:11:51 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 19:15:28 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 19:15:56 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 19:16:23 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 19:16:50 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 19:17:17 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=7 Atten=26 ]
Sep 7 19:17:44 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=8 Atten=26 ]
Sep 7 19:24:58 192.168.0.1 local5 Vigor: ADSL_Status:[Mode=8B States=SHOWTIME UpSpeed=1476000 DownSpeed=17592000 SNR=10 Atten=26 ] <- TV off

 

 

'That VDSL Cat'
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  Reply # 1625287 7-Sep-2016 22:03
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on a clean line 6dB snr should be okay.




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Any comments made are personal opinion and do not reflect directly on the position my current or past employers may have.

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