Kitz Forum
Broadband Related => ADSL Issues => Topic started by: sheddyian on February 18, 2013, 04:54:20 PM
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I thought I'd post this for interest to others, and because I'm open to suggestions.
Whilst trying to work out where the intermittently high error seconds and occasional loss of synch were coming from, I wandered around the house with an AM radio.
At around 700Khz I found a VERY loud buzzing sound. Now and again it would rhythmically drop out with an almost morse-like pulsing. dit dit dit dit.
Yesterday I blamed the bargain NAS and it's PSU, which I got off ebay and has caused me varying degrees of woe ever since, so I disconnected it.
But today I found the noise louder than ever.
Unplugging my gigabit switch made the sound decrease drastically in intensity, and the pulsing disappeared.
Aha! Switch or PSU faulty / bad design.
Except, wandering around the house, the noise came back. I could detect it everywhere in the house.
I went outside, and it was a lot quieter, but holding the radio to the house wall, I could hear it very clearly.
Up to the shed, it was very loud there too.
Near the phone line, I could hear the usual hiss of ADSL, but no buzz.
It seems that the noise is being radiated throughout the house ring main, and up to the shed via the mains cables, because isolating the shed from the mains made the radio fall silent. (not because the radio went off - it's battery :lol: But the loud buzz was replaced with a faint hiss when the mains was disconnected from the house).
Definitely mains bourne.
And network related, since I could quieten it by disconnecting a network switch.
Near the downstairs PC, the noise was very loud, disconnecting the gigabit switch there made it al but fall silent. Aha! So it's that! :graduate:
Replaced switch with a 100mbit one I had spare, only faint noise. But gets louder. So not the switch then >:(
Unplug PC (which was "soft" off anyway). Silence.
Plug PC in again - noise.
Power up PC, noise back but reduced.
Switching it on and off causes the noise to vary on the radio in a different room, and as I'm typing it's just started buzzing very loudly again, even though the PC in question is "soft" off.
I've now unplugged the suspect PC, and 700Khz is pretty much silent now.
So, I'm assuming here that the PC PSU is at fault. Radiating noise into the mains and into the network wiring via the NIC.
Fair assumption, or did I miss anything?
Ian
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Something to consider:= If it is mains borne then a power line filter as close to it as possible should see that route off. Possibly an internal one is dying ? I think it is possible to buy external filters (from Maplin?) without breaking the bank, which could reduce if not eliminate the problem. ( Some people swear by ferrite cores but which grade of ferrite ?)
The problem with a transistor radio is that it is quite difficult to tell relative strengths as it's AGC levels them out, you could supress the conducted component but the receiver still pick up direct radiation from the PSU at close range.
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Something to consider:= If it is mains borne then a power line filter as close to it as possible should see that route off. Possibly an internal one is dying ? I think it is possible to buy external filters (from Maplin?) without breaking the bank, which could reduce if not eliminate the problem. ( Some people swear by ferrite cores but which grade of ferrite ?)
The problem with a transistor radio is that it is quite difficult to tell relative strengths as it's AGC levels them out, you could supress the conducted component but the receiver still pick up direct radiation from the PSU at close range.
If it's the PC's internal ATX PSU (which it seems to be) then I'll get a replacement one. The noise could be heard on the radio all over the house, on both floors, and up the shed! That's not good.
I'm currently listening to the radio, still tuned to the frequency the noise was heard on. Earlier it was a gentle hiss, now the sun has gone down there are distant foreign stations breaking through now and again. But no interference. So does seem that it was the PC.
Just wait and see if the modem loses synch this evening.
Ian
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"I could detect it everywhere in the house".
Firstly, I personally would set the frequency to 612Khz as recommended by our Chief Engineers Office. Not sure what else you may be picking up at 700Khz ?? It would appear 'everything' ?? :)
'Noise' is obviously all around us, it's whether it's 'service affecting' noise !! You may well just be picking up normal noise' ?? I've been on a few cases whereby our 444B REIN tester screams at you 'It's here, it's here', when put next to a PSU or a baby monitor etc etc, when in reality it isn't actually a real-life 'Noise' issue.
The only true way to find out if you have REIN, is to test the spectral density across your circuit, to indeed see if the 'noise' is drowning the signal out. Also, you could have a poor MPF (pair of wires from Exchange to premises) showing a low AC Balance ?? This would mean that 'normal noise' would have an effect on your circuits stability.
I'm not trying to play down your efforts here, just making sure you don't throw out every PSU you have in the house for no reason. ;) :)
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Firstly, I personally would set the frequency to 612Khz as recommended by our Chief Engineers Office. Not sure what else you may be picking up at 700Khz ?? It would appear 'everything' ?? :)
Thanks for your reply, and I bow to your knowledge, sir :baby:
"around 700Khz" was because I stood next to the modem and slowly moved the dial from the low end upwards. And at around 700 got a very strong, loud buzzing noise, which I was suspicious of.
'Noise' is obviously all around us, it's whether it's 'service affecting' noise !! You may well just be picking up normal noise' ?? I've been on a few cases whereby our 444B REIN tester screams at you 'It's here, it's here', when put next to a PSU or a baby monitor etc etc, when in reality it isn't actually a real-life 'Noise' issue.
Ah now, that's the question. The symptom is high errored seconds and losing synch in the evening, sometimes repeatedly. Resynch after this is 2 - 3 K lower than usual.
The only true way to find out if you have REIN, is to test the spectral density across your circuit, to indeed see if the 'noise' is drowning the signal out. Also, you could have a poor MPF (pair of wires from Exchange to premises) showing a low AC Balance ?? This would mean that 'normal noise' would have an effect on your circuits stability.
I have absolutely no idea there - except that, up until this point, I've had a fast synching (20 - 21k) very reliable connection for over a year. So line condition (& AC Balance?) is/was OK ?
I'm not trying to play down your efforts here, just making sure you don't throw out every PSU you have in the house for no reason. ;) :)
No, not at all - that's why I posted here, to see if I was doing the right thing and leave it open to suggestions!
Maybe the meaning was lost a bit in my rambling post - I'd suspected several PSU's along the way, then ruled them out when the noise came back. But for the last 3 hours with the rogue PC disconnected, the noise has not returned. That one, then, is probably the source of the noise.
So, with the rogue PC switched off, I'm waiting to see what happens to the modem stability :)
Ian
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The trick is to leave it set to 612Khz, and then go looking for a 'Buzzing noise'. Bearing in mind 'false positives'. You are doing absolutely fabulously from your comments, and it would seem like you might have found a particular noise source ?
It really is a dark art, tracking REIN.
As an aside, and this may have been covered already ?? We have had issues with 21CN circuits dropping below 3dB SNR especially as night sets in. This causes problems with errors and L.O.S. events (Loss of service). I don't know which ISP you are with, what package you are on, or whether you are subject to DLM ?? Just thought it worth mentioning. :)
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As an aside, and this may have been covered already ?? We have had issues with 21CN circuits dropping below 3dB SNR especially as night sets in. This causes problems with errors and L.O.S. events (Loss of service). I don't know which ISP you are with, what package you are on, or whether you are subject to DLM ?? Just thought it worth mentioning. :)
I'm with TalkTalk, and it's a 21CN LLU circuit. Prior to this problem, I've not had any problems with LOS or high errors - I get a good synch around 20 - 21K. The reported noise margin rarely moves away from 6db, and if it does, not by much and not for long.
I believe there is DLM, as yet I've not seen it permanently increase the noise margin.
Out of interest, what's a good/bad figure for total error seconds? (this modem only reports an overall total). Currently it's showing 115 errors since I rebooted 3 1/4 hours ago. Good, bad, ok, mediocre?
Ian
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Hmmm ?? The £64 million dollar question !!!
Various ISP's used to allow between 10-20 Errored Seconds (or, CRC's) per minute. From an engineering perspective, I consider any kind of steady incrementation as a potential fault. Of course, it comes down to the almighty dollar, and we are to a degree, responsible to the ISP (not the EU), as they are paying our wages and it is their circuit. If the deem 15 ES's a minute to be ok, then who are 'we' to argue.
Long and short of it, I'm, no expert on what is good, bad or indifferent when it comes down to historical data. I tend to work on the 'Here and now' when faulting, I'm afraid. I'm sure some of the others will have a better line of input on this ??
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I'm with TalkTalk, and it's a 21CN LLU circuit.
All of us TT-ites in 'the know' will request the setting of a 6 dB target SNRM with the (TT) DLM disabled. Then, if required, adjustments of the DS target SNRM is made manually by tweaking with a Broadcom chip-based modem . . .
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Hmmm ?? The £64 million dollar question !!!
Various ISP's used to allow between 10-20 Errored Seconds (or, CRC's) per minute.
Well, that's a starting figure to consider.
Currently I still have synch, and have 128 total error seconds after 5 hours. Which I work out to be 0.42 per minute, if I'm doing the maths and understanding it correctly. So doesn't seem too bad?
From an engineering perspective, I consider any kind of steady incrementation as a potential fault.
Completely agree. I've got a record of sorts of different readings of error seconds and also noted how long it had been running for, so maybe I'll see if it's got better or worse.
But so far it's looking like the PC with the noisy PSU has been the cause of the problem.
Ian
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All of us TT-ites in 'the know' will request the setting of a 6 dB target SNRM with the (TT) DLM disabled. Then, if required, adjustments of the DS target SNRM is made manually by tweaking with a Broadcom chip-based modem . . .
I keep meaning to get TT to switch DLM off, and never get around to it.
That said, so far it's not caused me any problems, and if I was having reliability issues I think I might want DLM to try and improve things at a cost of lower synch speed, at least in the short term.
Also, nether of my current modems have the ability to have their target SNRM tweaked, as far as I can work out. :(
The TalkTalk one definitely doesn't; the room-heating TP-Link one does have some commands, that didn't seem to do anything when I tinkered, but haven't had a proper look yet.
Ian
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. . . nether of my current modems have the ability to have their target SNRM tweaked, as far as I can work out. :(
The TalkTalk one definitely doesn't; the room-heating TP-Link one does have some commands, that didn't seem to do anything when I tinkered, but haven't had a proper look yet.
Eric has very conveniently complied a list (http://wiki.kitz.co.uk/index.php?title=BCM_routers) of modem/routers which have Broadcom xDSL chipsets.
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Eric has very conveniently complied a list (http://wiki.kitz.co.uk/index.php?title=BCM_routers) of modem/routers which have Broadcom xDSL chipsets.
Ah yes, I'd had a look at that list the other day, a worthwhile resource. Sadly, my modem isn't on it.
The main chip on the modem has a weedy little heatsink stuck firmly to it, so I can't see the manufacturer. However, several other chips nearby have "Trend" printed on them, so that's probably a giveaway.
If I do go back to using this TP-Link modem, at the very least it's getting a much bigger heatsink, though I'm seriously considering a little fan. It gets worryingly hot. In my view, if you can't hold your finger on it for more than a few seconds, it's too hot.
Ian
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" The trick is to leave it set to 612Khz, and then go looking for a 'Buzzing noise'. Bearing in mind 'false positives'.
It really is a dark art, tracking REIN."
What is so special about 612 kHz ?
If it is IMPULSE noise, then it will have a wide spectrum ( Car ignition interference used to stretch all the way to Band I TV at 40 + MHz) and the more important point is to avoid confusion with a strong broadcast station. Yes it will have peaks but spark transmitters have been illegal since 1928 ! or is someone still commemeorating the Titanic ?!!!!
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It's not 'special', it's just the frequency our Chief Engineers Office recommend. I believe it's due to there not being much else around that particular frequency to cause disruption. However, one can hear a (I think it is) French radio station until approx. 0830 in a morning.
I'm no expert on the science, but I'm quite good in practice at finding REIN at 612Khz .............. not 700Khz, or 40Mhz, just 612Khz. ;) :)
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If you look at MW channels in the UK (http://www.mediumwaveradio.com/uk.php) you can see that 612kHz is fairly well removed from any UK transmitter frequencies. I guess that there's a degree of arbitrariness in the choice of that particular frequency, but it's not a bad choice.
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" It's not 'special', it's just the frequency our Chief Engineers Office recommend. I believe it's due to there not being much else around that particular frequency to cause disruption. However, one can hear a (I think it is) French radio station until approx. 0830 in a morning."
OK. I agree it is quite a good choice, but the general impression is that there IS something special, which suggests that ADSL works in some unique way. As to "Chief Engineers Office recommend", someone once told me of a Chief Engineers Office approved design which involved drilling a 1" diameter hole in a 1/2" strip !
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It seems to me that the choice of 612kHz as a frequency to detect REIN on is a bit arbitrary, given that ADSL uses frequencies from 25kHz up to 2200kHz.
In it's favour are (as pointed out) it's a generally quiet frequency with no UK stations on, and it's at the lower end of the spectrum where everyone will have some ADSL signal, regardless of line length or ADSL technology.
Maybe it's also got some harmonics further up that are relevant too?
I'm not disagreeing with the choice, if you've got to have a "standard", that one seems good. And now I know what it is, I'll be using it in future. Yesterday I just had a vague remembering that it was the lower end of the MW scale that was important, hence tuning around that end until I found noise, and trying to find where it came from.
And, interestingly, my radio dial appears to be misaligned a fair bit... I tried a different radio earlier, which has a quite basic digital display of the frequency. And discovered that I'd tuned my original radio far nearer to 612kHz than the 700kHz I thought it was on! :D
Update on the original problem : with the 'rogue' PC unplugged since early evening, I've had no ADSL disconnections or resynchs since, and the error seconds are currently showing as 375 after 18 1/4 hours of uptime, which I make as an average of 0.34 errors per minute.
Sadly the modem doesn't tell me error seconds in last hour or other divisions, just an overall total.
I've now ordered a new PSU for the PC ;)
Ian
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" It's not 'special', it's just the frequency our Chief Engineers Office recommend. I believe it's due to there not being much else around that particular frequency to cause disruption. However, one can hear a (I think it is) French radio station until approx. 0830 in a morning."
OK. I agree it is quite a good choice, but the general impression is that there IS something special, which suggests that ADSL works in some unique way. As to "Chief Engineers Office recommend", someone once told me of a Chief Engineers Office approved design which involved drilling a 1" diameter hole in a 1/2" strip !
Life's full of misquoted urban myths, JGO. Someone once told me that their Uncles deceased pet dog, contacted them to say Elvis was indeed driving a red London bus, on the moon. As regards this particular 'ChEO' advice, it's listed in all our official documents and compiled by people with lots of letters after their name, who spend all their time working on these issues.
I'd say it's more than just "a good choice". ;) ;D
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If thats the same French station I always picked up then it's at 624kHz It can be handy as a rough calibration for your radio.
612kHz is the next harmonic up from the key frequency near 300khz from which DSL has its foundation. Interfere with that and you'll really upset your DSL signal.
(MW radios don't go down as far as 306Khz so you make do with the next harmonic)
Each harmonic up has an effect although the magnitude reduces the further away from. It works much like musical notes; harmonics, semi tones etc. Be it sound, light, or electro magnetic.
Using the 444b is like using a radio, but the 444b broadcasts a wide range of radio frquencies all at the same time, unlike a typical radio where you concentrate on one (with a little bit of signal either side)
But tracking down a noise at a different frequency you are opening up yourself to chasing red herrings. Yes what you pick up @ 700kHz could well be having an effect on your DSL. ALthough the type of noise makes a difference as well. It's like having a conversation with some one and there is backround noise. Some noises are really distracting and throw your conversation off completely. Some noises seem to have little distraction. Although it would still be a little easyer without it.
DSL is the same, if the noise is similar to the digital signal of dsl then it has a greater effect on your speeds. This is why dsl still works dispite so much emf around us.
If it back feeds down the mains then you tend to get the noise popping up everywhere. The source could be anywhere in the noisy reigion, not just the centre. Switching fuses off on your consumerboard one by one may help in working out which group of items could be the suspect
Looks like you are finding out what locating a REIN fault is like. And why most engineers seem to run from tackling REIN. The 444b seems to be looked apon like a poison chalace.
You have to think back to your old school physics days, think about how magnatism forms around wires (hence radio waves) Think about the type of noise signal, in comparison to a dsl signal (the hissing noise you heard, Hold the radio by the router or phone cable to get an idea what it sounds like. Tune your car radio to 612kHz and you'll hear it each time you drive under a drop wire with DSL)
And think of all this EMF like an orchestra. Harmonies, but in electronics harmonies can be the opposite of making good music.
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Great info, Ezz. :)
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A few quick comments from The Cattery:
- The 2Wire 2700HGV and 2701HG-C devices actually quote the Downstream attenuation at 300 kHz: X.Y dB on their statistics pages.
- I use an ICOM IC-R5 as my receiver of choice for REIN investigations. With the squelch wide open, I will first check on 612 kHz and then repeat the sweep on 300 kHz.
- The noisiest switching mode PSUs that I have ever discovered are the white-cased, BT-branded ones that come with the Huawei HG612 modems, type 3B, supplied by Openreach as the active CPE for their GEA product!
- The quietest switching mode PSUs of the many that I have examined are the genuine 2Wire devices for the 2700HGV modem/routers. (A.k.a. the type 1 & type 2 BT Business Hub, Version 2.)
(Edited to insert the forgotten parameter that the 2Wire devices report -- having just powered one up to check. ;) )
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All fascinating, thank you :)
Quick update : since disconnecting the noisy PC, I've had 42 hours of uninterrupted connection, with a total of 811 errored seconds. During the peak of the fault, it would usually lose synch several times in an evening, so this is looking good.
burakkucat : I've used a very ordinary MW radio before to detect interference, and found various switch mode PSUs making noise, but only in their near vicinity. This noise was something else entirely, to be heard at the same level anywhere in the house as I walked around with the radio, only fading when I went outside, then increasing again as I went into the shed.
Given that unplugging LAN cables from switches would partially silence it, and I could also silence it in the shed by disconnecting the mains feed to that building, it seems it was being radiated through the LAN and the ring main.
Wonder if it was affecting the neighbour's ADSL ? :-[
I tried to make a recording of the noise on my phone, but I've not checked if it worked yet. If it did, I'll upload a recording later, if anyone might want to hear it :D
Ian
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Given that unplugging LAN cables from switches would partially silence it, and I could also silence it in the shed by disconnecting the mains feed to that building, it seems it was being radiated through the LAN and the ring main.
Yes, I agree. It clearly had two methods to propogate.
Wonder if it was affecting the neighbour's ADSL ? :-[
Well, it isn't, now! :-X
I tried to make a recording of the noise on my phone, but I've not checked if it worked yet. If it did, I'll upload a recording later, if anyone might want to hear it :D
Yes, please.
I just wish I had some means of recording the noise radiated from that Beattie branded PSU. It was quite distinctive, pulsing at approximately 2 Hz.
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Okay, I have recordings!
The first one was recorded whilst I was still trying to determine where the noise was coming from. I set the radio on the other side of the room to one of my Gigabit Ethernet switches.
The noise was to be found across a reasonable sweep of the bottom end of the AM radio dial. I believed the peak to be around 700kHz but now realise the dial is inaccurate, and it's a lot nearer to the magic 612kHz than I first thought.
The noise was very loud, tuning the radio to a pop music station, the music was quieter than the interference.
The pulsing sound you hear coincides with activity lights flashing on the switch, this is why I at first thought the switch or it's own PSU was to blame.
The pulsing is actually a dropping away of the noise, which is otherwise constant.
As you listen to the recording, you'll hear the pulsing stop - this is because I am at this point unplugging the Ethernet cables from the switch. I then try powering down the switch, but the noise remains constant.
There is one point where the sound fades away, this was either me retuning the radio or moving the mobile phone I was using to record the radio as I repositioned it.
I eventually tracked the noise down to a rogue Dell PC downstairs, which was switched off but plugged in to the mains, so the PSU was still "live".
The second recording is one I have just made, to show how that same frequency sounds with the rogue PC unplugged from the mains. Although it sounds as loud as the first, in actual fact I have turned the radio volume up full as I was concerned the sounds wouldn't be heard, they are MUCH quieter than the interference was. To me this now just sounds like typical AM static.
http://sheddyian.hopto.org/interference1.mp3 (http://sheddyian.hopto.org/interference1.mp3) < Interference 1 (This was heard all around the house)
http://sheddyian.hopto.org/interference2.mp3 (http://sheddyian.hopto.org/interference2.mp3) < Interference 2 (AM silence once the rogue PC was disconnected!)
Ian
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The first one I've heard before and yes I would say DSL would be affected.
Similar to the noise from some flat screen monitors (one of the most common culprits I found) But usually continuos. The stuttering... I've heard this exact noise before, but its driving me mad as to where and what it was. :wall:
You're right about REIN greatest hits. This tune is the type that is in your head and you go mad trying to remember the artist
Sounds like some appliance plugged into the mains thats back feeding the noise into a ring all right.
I would look to switch each ring off at the consumer board one at a time to see which causes the noise to stop then go along each item connected to that ring one by one, switching off and disconnecting.
The second noise is a bit hit and miss as to wether it would effect DSl. I've often heard similar without it making any difference.
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The first one I've heard before and yes I would say DSL would be affected.
Similar to the noise from some flat screen monitors (one of the most common culprits I found) But usually continuos. The stuttering... I've heard this exact noise before, but its driving me mad as to where and what it was. :wall:
You're right about REIN greatest hits. This tune is the type that is in your head and you go mad trying to remember the artist
Sounds like some appliance plugged into the mains thats back feeding the noise into a ring all right.
I would look to switch each ring off at the consumer board one at a time to see which causes the noise to stop then go along each item connected to that ring one by one, switching off and disconnecting.
The second noise is a bit hit and miss as to wether it would effect DSl. I've often heard similar without it making any difference.
The pulsing noise corresponded to the activity lights on the ethernet switch, so I think that was somehow modulating the interference. Disconnecting the switch from the mains stopped the pulsing, and the noise became continuous.
The source of the noise is a Dell Dimension 5100, when it's unplugged from the mains, the noise goes away. This is repeatable, so I'm confident it's the problem. I've ordered a new PSU for it now.
The second "noise" isn't really noise as far as I'm concerned, it's just a loud recording of AM background static really - I recorded it only to demonstrate a "before" and "after". Now that the Dell PC is disconnected (but everything else is powered as before, including the Ethernet switch that had been modulating the sound), the loud noise has gone away and the ADSL has remained in synch for 47 hours and counting.
Ian
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Thank you, Now I remember, it was a Netgear ethernet switch, 16 ports I think. Noise and stuttering. Once you mentioned the ethernet ports it came back. I'm sure it was that one.
Been going round East Anglia in my mind trying to remember
Now what's that 1982-83 tune is that that Lilly Allen lifted ? :hmm:
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Okay, I have recordings!
<snip>
http://sheddyian.hopto.org/interference1.mp3 (http://sheddyian.hopto.org/interference1.mp3) < Interference 1 (This was heard all around the house)
http://sheddyian.hopto.org/interference2.mp3 (http://sheddyian.hopto.org/interference2.mp3) < Interference 2 (AM silence once the rogue PC was disconnected!)
Very interesting to hear. Thank you. I must admit that I have never come across 'modulated' REIN, as in your first example, so that is something new for me to remember.
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Quick follow-up :
New ATX PSU arrived today, fitted it to the rogue PC.
PC working fine (though it was never exhibiting any problems itself), but more importantly.. radio tuned to 612kHz AM just gives me occasional distant foreign station fading in and out. Tuning up to 700kHz is equally noise free.
Sorted!
Anyone want to buy a used ATX PSU? Working order, many hidden features, sold as seen ;D
Ian
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Surely you will now open up that old PSU and take a look-see, just in case it could be repaired for use in your shed? ::)
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Surely you will now open up that old PSU and take a look-see, just in case it could be repaired for use in your shed? ::)
I'm certainly not throwing it away just yet! :D
I'm curious to see if there's anything obvious - bulging capacitors or something burnt out, but otherwise I'll salvage the fan, possibly the heatsink, and the rest can go to recycling.
I'll probably drop it in the small electronic appliance recycle bin in Sainsbury's car park. I'm sure they'll find a use for it :D
Ian
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Surely you will now open up that old PSU and take a look-see, just in case it could be repaired for use in your shed? ::)
I'm certainly not throwing it away just yet! :D
Ah ha! A fellow 'seasoned' adventurer, I do detect. ;)
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"It's baaaaaaaaaack!" >:(
Well, something is.
On Monday 18th I found the apparent cause of my high error seconds count and repeated disconnections during the evening - the Dell PSU which was radiating a lot of RF noise, detectable all over the house and in the shed, as already documented at length, above..
Since then I've had that computer disconnected from the mains, then I replaced the PSU. All has been well, no more disconnects, error seconds lower if not perfect. No problems with web pages not loading.
Then about an hour ago, web pages weren't loading. Modem still in synch. Logged in to modem and saw the error seconds climbing as I watched, then the modem lost synch.
Put the AM radio on, and heard this around 612kHz :
http://sheddyian.hopto.org/interference3.mp3 (http://sheddyian.hopto.org/interference3.mp3)
That wasn't there the other day!
It's not the original interference I heard, which sounded like this http://sheddyian.hopto.org/interference1.mp3 (http://sheddyian.hopto.org/interference1.mp3)
And after I'd isolated the PC causing that noise, the same frequency sounded like this
http://sheddyian.hopto.org/interference2.mp3 (http://sheddyian.hopto.org/interference2.mp3)
Which proves that noise wasn't there a few days ago.
I can hear it at varying levels from 522kHz up to 700+ kHz, peak seems to be just under 612Khz.
This time, switching off all computers, central heating, CFLs, TVs etc doesn't silence it. And unlike last time, I can detect it in the garden, and a little way up and down the road. At the very back of the garden it seems to be fading away.
>:(
Not sure what to do now. I lost synch, and resynched around 2 meg lower than expected.
This is different interference to before, and isn't coming from the PC that caused the original noise.
Did it cause my loss of synch? Is it causing my drop in synch speed?
I've had 6 days of trouble-free connection, but haven't listened to 612kHz for about 5 days, so can't be sure when the noise actually appeared. Naturally I'm assuming the noise has just started, and that's why I just lost synch but I can't know that for certain.
Thoughts?
Ian :rain:
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Oh dear. That doesn't sound too good. :(
Just to confirm -- with your incoming mains supply isolated by the 'big switch' being set to off, there is absolutely no change in the observed RFI?
I suspect you are now going to have to print out a scale map of your environs and then, from three physically separate locations measure the bearing for the minima (more accurate), thus the maximum will be +90 degrees of your reading. Plot those three bearings on your map and it should indicate the general area in which to search.
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Just to confirm -- with your incoming mains supply isolated by the 'big switch' being set to off, there is absolutely no change in the observed RFI?
Haven't done that yet - might wait until others don't need electricity :D
But I have tried individual things that are known for noise - anything with a switch mode PSU, TVs, digiboxes etc. That made no difference.
It does seem to be mains-borne, up to a point - I've just been up the shed, and found that isolating the power from the shed makes the noise quieter on the radio, but doesn't silence it.
Will try some more things later
Ian
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Well, I just happened to switch the radio back on, and the interference is gone. IN it's place is background hiss / slight static and a very distant foreign station occasionally breaking through.
Earlier, the interference was so strong it was causing the radio's "tuned" light to come on!
So, with the interference gone, I rebooted the modem - and got back my missing speed. All is well again.
For now :(
Between me wandering around trying to locate the source of the noise, and me discovering it had gone away by itself, nothing obvious has been switched on or off that I hadn't already tried.
Aren't intermittent problems the absolute worst ???
Ian
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Between me wandering around trying to locate the source of the noise, and me discovering it had gone away by itself, nothing obvious has been switched on or off that I hadn't already tried.
Aren't intermittent problems the absolute worst ???
Indeed they are. ;)
Just a thought. Could it have been due to a street light which had been energised but failed to light properly? After irritating you, it finally lit and the RFI disappeared (for now)? :-\
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Just a thought. Could it have been due to a street light which had been energised but failed to light properly? After irritating you, it finally lit and the RFI disappeared (for now)? :-\
That crossed my mind, which is why I took the radio for a walk up and down the road, but the interference fairly quickly fades out, and doesn't seem as strong at the roadside as it is in the house. Likewise, at the far back of the garden, where there are more street lights nearby, the interference is practically silent, so I don't think it's street lights. And I did look to see if any were flickering or unlit, all that I could seel seemed to be working ok
Meanwhile...
Since the last post, the noise is back once more.
I'd switched the radio on again, and recorded the "silence" for research purposes :graduate:. When I'd done that, I left the radio on, enjoying it's gentle hissing, and went back to the computer (which had been switched on all the time). After a short while, the noise started coming back, and lo! web pages started refusing to load.
I used telnet to connect to the modem and I could see the error seconds rapidly rising, from 80 to 200 in less than a minute. Shortly afterwards the modem lost synch again, and disconnected.
The interference is across quite a large swathe of the AM band. I switched the computers off (to rule out their interference) and made a little Youtube of me scanning the AM band on a portable radio, which you can watch and listen to here http://youtu.be/kzWTGEa-ReU (http://youtu.be/kzWTGEa-ReU)
With everything unplugged from the mains in that room (including the modem), I can still hear the noise, so it's not very nearby electrical equipment there that's causing it.
Edit :
This was the noise at around 6:20pm today : http://sheddyian.hopto.org/interference3.mp3 (http://sheddyian.hopto.org/interference3.mp3)
Then around 8pm I discovered the noise had gone, and recorded this on exactly the same frequency as the above recording. : http://sheddyian.hopto.org/interference4.mp3 (http://sheddyian.hopto.org/interference4.mp3)
But now it's back again again >:(
Ian
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:hmm: Hmm . . . one of your immediate neighbours could be suspected -- once you have performed the 'big switch to off' experiment in your own home.
(I wonder if Big Nellie's electropathic belt is showing signs of a corona discharge? :-X )
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:hmm: Hmm . . . one of your immediate neighbours could be suspected -- once you have performed the 'big switch to off' experiment in your own home.
Well, on the plus side, the noise seems to be loudest inside this house, though I could detect it outdoors as well.
I did wander up the driveway to the next door neighbour, and whilst I could hear it there, it didn't seem as strong.
If it comes back, I'll do the same again, or I'll ask if I can wander around their house with an AM radio ???
Not long after my previous posting, I found the noise had gone again, and it hasn't returned since, as far as I can tell (ie the modem has stayed in synch for 20 hours), though the error seconds count was higher than I'd expect (1300+ in 20 hours).
Currently there's no noise, I rebooted the modem and it resynched at 20k. Error seconds are around 10 an hour. This is what I'd expect, and how it's been pretty much for the last 14 months, until a few weeks ago.
If anyone can suggest what might cause this sort of noise, please let me know :ouch:
http://sheddyian.hopto.org/interference3.mp3 (http://sheddyian.hopto.org/interference3.mp3)
(to me, that sounds like putting the radio on top of a CRT TV! There were no CRT TVs anywhere near the radio when I recorded that, nor monitors, and that noise could be heard throughout the house as I wandered around with the radio)
Ian :rain:
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Surely you will now open up that old PSU and take a look-see, just in case it could be repaired for use in your shed? ::)
I have now had a look at the suspect PSU. And, lo, there is a bulging capacitor. (might not be that obvious in the picture, but it's a significant bulging). Now wondering if it's worth replacing that cap, to bin the whole PSU, or to replace other caps as well. (which ones?)
Still leaves a bit of a puzzle though.
I am confident that this PSU was generating noise on the AM band around 612Khz. I recorded it, and could silence it or create it by switching this PSU off or on. It could be detected all around the house.
Despite isolating, then removing this faulty PSU, the ADSL disconnections resumed around 7 days later, and continue intermittently. A different, but strong, noise can be heard on AM at 612Khz nd above, all around the house during the intermittent problem period.
Prior to this, I'd had 14 months problem-free, high speed connection.
Still trying to find current (VERY intermittent) source of noise.
Meanwhile, here's a picture of a bulging cap. It's quite pronounced in real life (might actually be leaking slightly) but photo doesn't show it as clearly as I'd intended. All the others seem fine.
Should I try replacing only that one, or others as well?
Ian
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Oh yes. I can see the bulge.
Erm . . . isn't there a saying "Nothing ventured, nothing gained."? ::) If you feel up to it then, as the Nike slogan said, "Just Do It". :)
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*sigh* :rain:
Interference is back, pages refusing to load or hanging. Currently showing 300+ errors in 15 minutes, resynched at much lower speed.
I went to fuse box, and switched EVERYTHING off via the master switch. House in darkness, silence. Except for my battery radio. Which was still buzzing away very loudly.
So, the interference isn't caused by anything in this house.
A wander around the garden and the street shows the noise to be centred on my house and the detached neighbours. In front of their garage door the noise is very loud (they have two freezers in there.. I wonder?) Out in the street, noise less strong. Up and down the road it quickly fades away. Standing underneath nearby street lights makes no difference, so it's probably not those.
Will speak to neighbours when they get back. Seems to be worse on a Sunday evening, even when they're out - so what is it that's different about that day?
Still, I get on well with the neighbours, and I'll have to play it down a bit because they'll be genuinely embarrassed if they think it's their fault!
An hour ago, this post was going to be an update saying it was all going fairly well, and that I'd relocated the modem to be as close as possible to the incoming BT line to the house. There's no more than 2 metres of cabling above ground to the modem now. (Previously it was nearer 6, straight up the wall , which I thought might make a good aerial, so I eliminated that).
Hey ho. Still, I've made progress - next stop, neighbours!
Ian
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Brief update : Earlier I went around the neighbours house with my radio, explained the situation, switched radio on and they heard the loud buzzing across the bottom end of the MW dial.
Wandered around their house, it did seem loud there, but couldn't pinpoint it.
Loud in the garage which contains two small freezers, Switched freezers off. Noise continues.
Loud in their hallway, near cupboard with fuse box.
I ask if I can come back when it's more convenient, they suggest I carry on for a bit, and that I switch mains off.
Switch off the main switch on their fuse board. Noise continues as before.
So it's not being generated by mains equipment in their house.
And not by mains equipment in my house (also switched off earlier).
Yet the noise seems to centre around these two houses.
Noise is constant whilst present (not pulsing) but comes and goes over a period of hours.
Appeared around dusk
Disappeared around 8pm
Then came back a bit later
By midnight it had gone once more.
But doesn't happen EVERY night (Sunday seems popular!)
The AM radio noise and high error seconds/disconnects seem to be related. If I cause the modem to resynch whilst the AM noise is present, I get a connection speed around 2K lower than otherwise expected. Whilst the AM noise is present, the modem records high error seconds, which stabilise once the AM noise has gone.
Anyone have any thoughts as to what to try next?
Ian
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That is quite a mystery. :o
For both your own and your neighbour's house, do you have any idea of the route the incoming electricity supply cables takes from the street to your respective main fuses? I am wondering if there could be a defect in the electrical distribution cable close to your houses. But that does not account for the observed timing effect. ???
Perhaps you could interest Walter to trundle his wheel-barrow in your direction . . . :-X
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The neighbour shouldn't be on the same phase so if its conducted noise then its coming through neutral (which in theory should be grounded at the substation, but you should never assume it is - many connections aren't grounded).
Example - house #1 will be connected to the red phase; house #2 will be connected to green; house #3 will be connected to blue; house #4 will be connected to red; house #5 will be connected to green etc etc Only earth and neutral will be "common" to all the houses.
I'd be inclined to go for a walk up and down the road checking every third house as they'll be on the same phase. If the noise isn't varying at all (just decreasing) then its unlikely to be conducted emissions and if it is then its more than likely propagating over the neutral wire. Having said that, turning off the mains power at the fusebox doesn't disconnect neutral from the internal wiring so it could be conducted emissions causing the initial problem.
Your last recording sounds like a dodgy ballast (or possibly a wall-wart PSU) to me, so I'd also watch for that and given the hours this happens it may well be external lighting at fault.
Not an easy one to find....
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For both your own and your neighbour's house, do you have any idea of the route the incoming electricity supply cables takes from the street to your respective main fuses? I am wondering if there could be a defect in the electrical distribution cable close to your houses. But that does not account for the observed timing effect. ???
The timing effect is the killer here. Sunday evening seems to be problematic. But why?
The neighbours attend church on a Sunday, and also don't watch TV on a Sunday, but DO play an electric organ (the husband plays organ in the church they attend as well). Potential pattern match there - different behaviours on the day I get interference!
BUT
It seems to start when they're out at Church in the evening.
Wandering around their house with a radio couldn't pinpoint it's source
Switching off ALL their electric didn't silence it.
I will keep the radio switched on a lot more, and see if it comes back (perhaps at reduced strength) at other times.
Sunday evening seems to be the day to lose synch, but I have seen higher (but not drastic) error levels during the week as well.
And just to recap, this recording from Sunday 24th February is the noise I was hearing yesterday (Sunday 3rd March) http://sheddyian.hopto.org/interference3.mp3 (http://sheddyian.hopto.org/interference3.mp3) across most of the lower end of the MW band, certainly on/around 612kHz.
The interference was so strong in the neighbours house that I couldn't find Radio 5 Live, which usually comes in strong around here!
Ian
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If you've switched off ALL the electric at the mains board, then it can't be emanating from your neighbours house and you're wasting precious time.
Haven't time to read back through this thread, but are you fed Overhead, or Underground ??
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If you've switched off ALL the electric at the mains board, then it can't be emanating from your neighbours house and you're wasting precious time.
Haven't time to read back through this thread, but are you fed Overhead, or Underground ??
My last post wasn't very clear, I'd intended it to be a "here's the oddity of it" - they appear to be prime suspects with significantly different behaviour on the day the noise appears, and it being very strong in their house YET it can't be them because switching their mains off didn't silence the noise even slightly.
So, yes, I have ruled them out.
The phone wires are underground all the way, excepting the last 2 metres which runs up the wall in the middle of our semi-detached to an external grey junction box. This feeds us and immediate neighbour. (this is different neighbour to the one I thought the noise came from). When present, noise is quietest on this side of the house.
Mains electric also comes in underground, also on front of house but on other side.
Have quickly scribbled a plan, in case it's of any help to understanding what's going on.
Ian
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Probably a silly question, but how have you eliminated Neighbour #1 and Neighbour #4 from being the cause?
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If you've switched off ALL the electric at the mains board, then it can't be emanating from your neighbours house and you're wasting precious time.
Mmmm not quite.
Do they have an alarm system? The thought occurs as there seems to be a corrrelation between them being "out" on Sundays and the problem occurring.
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If you've switched off ALL the electric at the mains board, then it can't be emanating from your neighbours house and you're wasting precious time.
Mmmm not quite.
Do they have an alarm system? The thought occurs as there seems to be a corrrelation between them being "out" on Sundays and the problem occurring.
If i'm reading this right (and I often don't ;D), Ian has switched off all the electric at the mains (in the neighbours house), and the noise is still present ?? Whether the alarm is set or unset with the electric back on, it shouldn't play a part, as the noise is there regardless ?
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The alarm panel will be battery backed up so killing the power will have no effect on it at all - if its generating noise then the noise will still be present whether mains is on or off.
I doubt that's it but the cabling on alarms is just bellwire and generally about the right length to radiate MW/HF. There's all sorts of different sensors as well - we have dual PIR/microwave sensors but the microwave element of the sensor is only turned on when the alarm is set - so there's plenty of potential for issues.
The only time correlation Ian has managed to make is when the neighbours are off out godbothering so maybe worth a try.
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Probably a silly question, but how have you eliminated Neighbour #1 and Neighbour #4 from being the cause?
I haven't directly eliminated them, no, because the apparent centre of the noise was either myself or neighbour "3".
Neighbour "3" doesn't have an alarm, and aside from a programmable thermostat for their heating which seemed to be battery powered, I can't see anything else that might be making noise without mains power. The stat made no noise, with or without power!
The noise was a lot quieter around "1" and "4".
HOWEVER
I've just been round to neighbour "3" for a chat, and took my radio to demonstrate that the noise was gone today.
Or, as it turns out, gone in my house, but still present in theirs, albeit quieter than last night.
And the strongest source is their party wall with "4". If I go into "3"'s garden, hold the radio close to the house and the party wall, it's worst in that corner (back corner, farthest from road).
So it looks like it could be coming from "4".
A walk around the block shows that I can't detect it at all from outside, only in "3"'s house where it adjoins "4"
But it's odd that last night the strongest point appeared to be centred between "2" and "3". Now it's between "3" and "4".
How could this be?
I don't know the people at "4" at all, so I've go to play this carefully so I don't look mad, turning up on their doorstep asking if I can walk around their house listening to noise on my radio.... ???
Ian
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If i'm reading this right (and I often don't ;D), Ian has switched off all the electric at the mains (in the neighbours house), and the noise is still present
Yes, that's right. Switching off mains in my house "2" and neighbour house "3" does nothing to silence or even reduce the noise heard on the AM radio when it's present.
However, my suspicions are now on house "4" which seems to be emanating the same noise, though at reduced intensity compared with last night.
Ian
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Having said that, turning off the mains power at the fusebox doesn't disconnect neutral from the internal wiring so it could be conducted emissions causing the initial problem.
I thought that all main switches were double-pole? ???
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Having said that, turning off the mains power at the fusebox doesn't disconnect neutral from the internal wiring so it could be conducted emissions causing the initial problem.
I thought that all main switches were double-pole? ???
Good point there - I'm pretty sure they are, as the incoming Live & Neutral from the meter go straight to the main switch.
As an aside, I think all but the cheapest switched mains sockets are double pole too.
Ian
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Having said that, turning off the mains power at the fusebox doesn't disconnect neutral from the internal wiring so it could be conducted emissions causing the initial problem.
I thought that all main switches were double-pole? ???
Why would you think that?
The way this is supposed to work in the UK is that you fuse live and RCD earth in the premises. You fuse live at the tails on the meter.
Edit - to clarify, the only current path to neutral/earth is via the fused/switched live side so why would you expect switches that isolate neutral?
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All modern split-board consumer units, should use the 100Amp double-pole breaker.
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Having said that, turning off the mains power at the fusebox doesn't disconnect neutral from the internal wiring so it could be conducted emissions causing the initial problem.
I thought that all main switches were double-pole? ???
Why would you think that?
The way this is supposed to work in the UK is that you fuse live and RCD earth in the premises. You fuse live at the tails on the meter.
Edit - to clarify, the only current path to neutral/earth is via the fused/switched live side so why would you expect switches that isolate neutral?
I don't want to argue about this but my choice of wording ("I thought that . . .") was really just me being tactful.
To be honest, every main isolator switch that I have examined (and that is a significant number -- but not as many as oldfogy, retired electrician and Black Sheep, ex-electrician) have all been double-pole, without exception. If I could be bothered to do so, I could remove the appropriate covers, photograph both main isolator switches (here in The Cattery) and post the images. Viewers of those images will see double-pole switches.
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After a good few weeks of relatively trouble-free ADSL, tonight the modem lost synch again, and re-synched around 2k lower than is typical. Switching on the Medium Wave radio, I can hear a very loud buzzing that's been absent for some time.
The problem has occurred on a Sunday evening once more, although there is one difference - the neighbours 2 doors up, whom I previously suspected, are away on holiday. No cars on drive, no lights in house.
Interference once more seems loudest from immediate neighbours, even though I'd assumed I'd ruled them out when I switched off their mains at the fuse box and the interference carried on.
And then, at 23:03 the noise (which I was quietly listening to on the radio) was interrupted with a click and then it faded away over perhaps 20 seconds.
The previously noisy MW frequency is now once more silent. And a reboot of my modem gives me normal expected synch speeds.
Baffled now.
What would YOU do next?
Ian
ps occurrence of noise gave me chance to re-test a previous experiment, namely running the modem from a 12 volt battery. When I'd done this test before, there was no interference, and I couldn't detect any difference between battery or mains adaptor operation.
Since this noise is mains and RF borne, I wondered if disconnecting the modem from the mains would achieve anything.
The answer was around 500k gain when switching to battery during the RF interference.
Not sure if that's very significant though.
Am currently still on battery power, wondering how long it will run for :)
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How very perplexing! :-\
It seems as if the only way this problem will be resolved is by you acquiring the services of a flock of Black Sheep, SFIs and PTOs from the ranks of Bettie's elite.
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Hmmm, tis indeed a tricky one ??
I'm afraid that, due to the random timings of the REIN, it would probably end up at the door of the PTO's, after an initial task has been raised through the normal fault channels with the ISP. The PTO's have far more advanced equipment than us mere mortals and are more likely to be able to attend site on 'Overtime', again, due to the lateness of the REIN emission. I know this to be the case as I've had call to bring them in on a couple of jobs on my patch, in the past.
I haven't got the time to pour over the whole thread again, but all this would only take effect if the full set of criteria has been met. IE: A PQT pass with an AC Balance of at least -50dB, preferably -60dB. RF3 and SSFP installed. Sometimes, the REIN team will request an E and D side change, but they are just desk-jockeys who are script-reading and I will politely explain that this is not required. Sometimes, I kid you not, they will have the engineer put their van radio on 612Khz and turn the volume up, then they will determine if it's REIN or not from what they hear on the other end of the phone.
Again, as a REIN trained engineer myself, such a ludicrous request is usually met with short thrift.
Obviously, this particular circuit isn't subject to prolonged REIN conditions, so the EU's claims (via their ISP's retrospective monitoring tool) will have to provide evidence of when it is actually occurring. If it's a classic BT DSL circuit, then we have the facility (WHOOSH) to view the circuit ourselves, which is a great help. Trying to get the necessary info from a Level 1 call-centre advisor is like pulling teeth, not their fault as they're probably not trained on what to look for ??.
I have to be honest, the OP is gonna have trouble getting this resolved if it is REIN. The intermittency of it makes it damned near impossible to predict when to attend site. Bear in mind nobody is paying 'us' (and at OT rates) to find the REIN, it really would be hard to justify dipping into the coffers, with a good chance of not getting a result.
Sorry to be all negative, or realistic as I'd call it :), but I think it's a case of sheddyian collating as much evidence as he can per-chance he does pursue it via his ISP.
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Hmmm, tis indeed a tricky one ??
Sorry to be all negative, or realistic as I'd call it :), but I think it's a case of sheddyian collating as much evidence as he can per-chance he does pursue it via his ISP.
I quite accept that it's going to be tricky to resolve, and your comments and insight are helpful, not negative :)
As you say, realistic.
I always hate intermittent problems, especially where they seem to defy logic (as in this case).
Since Sunday, the connection has been fine.
Wednesday has also been a popular day for interference, so well see what happens tomorrow.
Curiously, Wednesday is also a day that the immediate neighbours do church-related activity.
Wednesday and Sunday. The days I'm most likely to get the REIN problem.
Wonder if they're praying too hard and it's interfering with my router and MW radio? :-X
Ian
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They do say that God works......................... nah. too corny by far. ;) ;D
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Perhaps, when time permits, TobyPTO (http://forum.kitz.co.uk/index.php?action=profile;u=7142) could offer some suggestions as to the techniques which can be used when attempting to trace such an intermittent source of interference? :-\
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It ocurred to me earlier that when I switched off neighbours mains electricity at the fuse box, I adh the MW radio in their housem and it continued to buzz away loudly.
But what if that's irrelevant?
In MY house, noise around 600 - 700Mhz on my MW radio will co-incide with loss of synch, lower speed resynch and high CRC errors.
Maybe the noise is ALWAYS present in their house, for whatever reason?
Yet their activity seems to influence the interference.
So, when convenient, I need to switch off their mains electric then listen to interference in MY house. Did it have any effect?
Thankfully, they are very amenable to all this, and I've explained that I don't blame them personally. At worse it's some equipment of theirs causing this, but they know nothing of it. Or that it's utterly nothing to do with them. I've stressed that it's a puzzle I'd like to solve :)
Ian
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Update :
After a trouble free week (including Wednesday evening, which has been a popular time for problems in the past), on Sunday evening around 7pm I lost synch and reconnected around 2K lower than usual. Switching on the MW radio showed the loud hum to be back.
Later that evening (around 11:30pm) I switched the radio on again and the hum was gone, so I rebooted the router and got my lost 2K back. I noticed that in the intervening 3 hours I'd clocked up 6,000 error seconds! (10 - 15 an hour is more usual for me).
When the modem lost synch the immediate neighbours were out, the the ones further up the road were in - though they were on holiday last week when this last happened ???
Why Sunday evenings and occasionally Wednesday evenings? ???
Trying to approach this logically : What electrical equipment might someone have on a timer or somesuch, that only runs once a week, on Sunday evening, for 3 hours or so?
Ian
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"Trying to approach this logically : What electrical equipment might someone have on a timer or somesuch, that only runs once a week, on Sunday evening, for 3 hours or so?"
Watering for greenhouse plants ?
Just a memory jog, most portable radios have a ferrite rod aerial which is directional. It isn't as good as a proper DF frame aerial and off hand I don't know the angle of the nulls in relation to the aerial ( always use nulls, they are sharper, maxima are flat) but afer a dummy run on the local radio station, so you know the location, two or three checks should may localise the RFI source.
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Just a memory jog, most portable radios have a ferrite rod aerial which is directional. It isn't as good as a proper DF frame aerial and off hand I don't know the angle of the nulls in relation to the aerial ( always use nulls, they are sharper, maxima are flat) but afer a dummy run on the local radio station, so you know the location, two or three checks should may localise the RFI source.
I was looking this up the other day, to check which way the aerial is most receptive :D
.. which is basically along the length of the ferrite coil I think, with the nulls at each end.
max
null ===ferrite=== null
max
(I found a site with a better picture than that, can't find it again now...)
Now, with the radio aligned along the max of the ferrite, the interference is strong enough to cause the "tuned" led to light.
And certainly walking along the street I can determine where the interference fades out, and get a rough idea of direction (the two neighbours houses, but I can't decide which)
But you say to use the nulls to locate the signal? How would I go about doing that? ???
Thanks
Ian
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"I was looking this up the other day, to check which way the aerial is most receptive :D
.. which is basically along the length of the ferrite coil I think, with the nulls at each end."
That is what I thought but it is read across from a loop, so wasn't sure.
"But you say to use the nulls to locate the signal? How would I go about doing that?"
The idea is that the rate of change of signal with angle is greatest at a null and zero at a peak so the nulls define a direction better. The technique is to find the directions where the signal drops below receiver noise and returns the other side and average them to approximate the true null. Repeat from two or three locations to sort out the 180 degree ambiguity of a single bearing and then move in that direction to narrow the zero signal angular range.
If you get too close the radiator isn't a point source so you can't get a clean bearing, but that puts you quite close. ( I seem to remeber reading that the French Resistance used to use a telephone wire miles long as an aerial to fool the Gestapo, and this could be replicated with overhead power lines and a powerful interference source - but that isn't a faulty appliance it is a*!&? spark transmitter, banned since 1938 ! )
P.S. perhaps I should add thet the receiver AGC tries to flatten out the peaks so nulls are a better bet for this reason too.
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I am so pleased to find out about the problems you are having. No, it is not because i'm a nasty piece of work, it's just that I have been having EXACTLY the same problem and I am running out of hair to pull out !
The sounds of the buzzing that you posted were spot on. EXACTLY the same, although i'm getting it at different times. In the colder weather, I had the interference between 1800hrs and 2100hrs, during which time my errors rocketed from nil to multi-millions. Just when I think I have found the culprit and get a few days of nil errors, it then comes back when least expected with a vengeance. It now seems to occur Saturday and Sunday evenings.
Can anybody recommend a mains filter which would give me a source of clean power to the hub just in case it is the mains which is the source of this interference ? I have already tried cat6 cables and am running out of options......... :(
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Thanks for suggestions re aerials and locating the source of the interference. Wednesday evening went without incident, and everything has been fine since last Sunday - so I await this Sunday with interest, especially as the suspect-neighbours are away again for a bank holiday caravan break :)
I did try a wander up and down the street the other evening when I was NOT having interference issues, and the radio was largely silent - though there was a slight buzz around the immediate neighbours house, which was interesting.
Ian
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The sounds of the buzzing that you posted were spot on. EXACTLY the same, although i'm getting it at different times. In the colder weather, I had the interference between 1800hrs and 2100hrs, during which time my errors rocketed from nil to multi-millions. Just when I think I have found the culprit and get a few days of nil errors, it then comes back when least expected with a vengeance. It now seems to occur Saturday and Sunday evenings.
Can anybody recommend a mains filter which would give me a source of clean power to the hub just in case it is the mains which is the source of this interference ? I have already tried cat6 cables and am running out of options......... :(
That does sound quite similar to my problem - though Saturdays is usually trouble-free for me :D
My feeling on this is that a mains filter won't help.
If you can hear the noise on an AM radio, it's being radiated out from the source(s) and so your router/phone cabling/lan cabling/computer cabling etc etc will all be susceptible to picking it up and it getting into the router.
Even if you were able to put all these things in a Faraday cage (to eliminate radio frequency interference) and run from a 100% clean power feed, chances are the phone line under the road or on the poles will be picking it up.
(My own experiment with disconnecting my router/modem from the mains and running it from a 12 volt battery proved this, I still suffered a loss in speed until the interference ceased)
It's a case of tracking the noise down and removing it at source. Which I initially found easy (I discovered a faulty computer PSU making a dreadful noise on AM) but then later discovered there was another source outside of my house that I've yet to pin down.
Ian
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I am currently monitoring the router stats in order to identify some sort of pattern regarding the timing of the interference, after all, I don't know of any rein engineer who can locate the source of interference if the interference isn't occurring when he is actually present...........I'll keep you informed.......
Good luck............ >:(
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Just to show the sort of interference I am getting at this moment......
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Does anyone know why the errors accumulate on the download side but not on the upload side ? Surely the interference would affect the line in both directions, or am I mistaken ?
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The upload operates at the lower end of the frequency spectrum
The download operates at the higher end of the frequency spectrum.
(and the voice calls operates at the bottom of the spectrum)
So it depends at what frequency is the interference happening.
Most of the likely sources of interference pump out the cr*p at frequencies which are in the download section of the spectrum as used by ADSL.
Added to which, the upload on ADSL is more lightly loaded as BT/DSLAM manufacturers won't allow it to operate at full throttle that it could if really pushed - unlike the download. So there is less scope for errors to occur on the upload in the first place as there is plenty of "slack".
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Thanks for that :)
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Hi I'm new to the forum but have worked in the tv and comms industry for years, spent a lot of time sifting rfi problems on tv a d radio's over the years, these days it's worse with DVB and more difacult to fully resolve.
This noise may not be one single thing it could be a combination of everything and normally be present on the live line but only one item is perhaps directing it onto the earth or neutral line, something like a heating stat stat could do it if porly installed, even if the mains is off the stat if a manual or battery one would still switch even if the power is off, as has been said the neutral will be isolated when you shut off the main isolator but the earth is not, your house cabling acts as an antenna at such low frequencys. The whole street could be just as bad.
What kind of earth system is your house and street on ? If you had your own rod it's TT. Then you have TNS & TNCS , the last two can make a big difference as for one the earth and neutral combined at the point of entry at your house where as the other has a separate earth back to the transformer then combined there, with the combined earth at your house there are also earth rods added by the DNO at various points on the route from the transformer and these could be picking something up.
One common thing iv found over the years is people often assume that finding the source and stopping it is the solution however often it's not, you would be better trying to limiting its affect on your system, iv recently seen some one replaced the bt incoming cable from the box out side to their phone point with screened cat 6 and earthed the shield, never under estimate ferrite beads on cables, you could also try running your router on 12 battery when the noise is causing the most problems to see if a clean supply helps,(most routers are 12v)
One last though, when the noise is happening have you tried disconnecting your router? Perhaps the noise in on the line it's self ?
Often their is no one solution but a combination of things can improve problems.
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" never under estimate ferrite beads on cables, "
YES but WHICH ferrite bead ? There are many grades of ferrite with permeabiliies ranging from ten into the thousands, for use at various frequencies. and size anything from 2 mm to 2 cm diameter.
I agree they can be very useful but " a ferrite bead" is like "a car" - a model T or a BMW ? Also I know of one instance where the position along the cable made a considertable difference to performance !
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re Hundleton1
Apologies for the delay in replying. I've read and digested your post at least half a dozen times, and you've given me a lot to think about, and look into. Unfortunately i'm no expert at this and I am extremely grateful for any ideas that can rectify this problem. Your point about the screened cat6 cable is something I've already set in motion. I shall keep you updated......