Induction loop interference

[seeingtrees]

Hello, I hope someone can perhaps give me some advice.

 

I found this thread here on the forum and it is in the same area I am having a problem, but not quite of the same nature, so I thought I'd ask.

http://www.blue-room.org.uk/index.php?showtopic=22650

 

 

I began picking up tv stations a few weeks ago on my strats and p-bass and after some investigation I worked out it was satelitte channels I was picking up. It is a strong enough signal to be able to make out what is going on.

 

A bit more investigation and speaking to neighbours and I traced it to a downstairs neighbour who regularly watches the channel I am picking up.

 

We then worked out that I have only been getting interference since she had an induction loop system installed in her flat. We then switched the loop on and off while I checked what was happening with my guitars/bass and established that when her loop is off, my interference goes too.

 

Her loop is on all the time and plugged directly into her Sky satelitte system, the cable of which runs up my outside wall and the dish is more or less above my flat.

 

The thing is, she lives 4 floors below me in a concrete and brick building. I'm puzzled why so far above the loop I am getting such strong interference.

 

I've tried playing in all the rooms in my flat but the level of interference is constant. As it is regardless of which leads I use and whether I go through a pre amp, a mixer or an amp.

 

I need this sorted as I make part of my living from being a musician and the interference level is high enough to be there all the time and makes playing difficult and recording, impossible.

 

The company that installed her loop aren't being very helpful and don't seem to have an answer to how to solve this.

 

Can anyone help?

 

Thank you.

[paulears]

The small portable loop systems that are placed near the viewing seat are normally best for people with hearing problems - a full blown loop allowing listening anywhere in the flat will radiate up and down. I suspect the steel framed building kind of encloses you in the strong signal area.

 

Bearing in mind the lack of any proper legal education, I have found references in the various Wireless Telegraphy Acts and amendments to induction loop systems, which suggests that some protection from interference should be available.

 

In most cases, loop design prevents any substantial signal strength outside the loop - but you are still within it, just higher up. I guess taking the carpet up and foiling the entire floor could work, but is a bit drastic. Depending on your need to remain friendly with the neighbours, I reckon a solicitors letter to the installers may be the way forward. It does look as if their design was not carried out with any thoughts to unwanted emissions in the vertical direction! Best of luck!

[seeingtrees]

The small portable loop systems that are placed near the viewing seat are normally best for people with hearing problems - a full blown loop allowing listening anywhere in the flat will radiate up and down. I suspect the steel framed building kind of encloses you in the strong signal area.

 

Bearing in mind the lack of any proper legal education, I have found references in the various Wireless Telegraphy Acts and amendments to induction loop systems, which suggests that some protection from interference should be available.

 

In most cases, loop design prevents any substantial signal strength outside the loop - but you are still within it, just higher up. I guess taking the carpet up and foiling the entire floor could work, but is a bit drastic. Depending on your need to remain friendly with the neighbours, I reckon a solicitors letter to the installers may be the way forward. It does look as if their design was not carried out with any thoughts to unwanted emissions in the vertical direction! Best of luck!

 

Thank you. Your reply is very helpful indeed. The walls and floors are made of reinforced concrete and also all the floors have an additional layer of metal consisting of (now broken) underfloor heating systems of metal mesh embedded into the concrete so your explanation sounds like the reason why I am receiving the signal so strongly.

 

I now have some thinking about what to do here as I do get on very well with my neighbour, help her out with many things and wouldn't want to cause her any bother, but on the other hand, this is placing an unreasonable restriction on my activities.

 

I'll look into the smaller loop system you mention.

 

Thanks again.

[paulears]

Ampetronics do a nice portable system that is low power and portable.

[thetechguru]

Hi

The common element in all of this is the mains supply, I would expect moving around in your flat would change the level of 'interference' due to the position of you and your guitar to the induction loop, if it is radiated field pick up.

Q - does the interference change if you move the orientation of the pick ups - if it does not change it is not the loop pick up on the guitar.

 

Try a battery powered amp or another mains amp to eliminate mains bourne interference - if it is still there beg/borrow an induction loop measuring device and see if you have a strong field within your flat.

Do you know the make and model of the loop amplifier. For a domestic sitting room a small field is all that is required but if a large amp has been installed by someone who does not have the necessary skills and background they should be taken to task.

 

This has been a common problem on single wound pick ups on guitars and sometimes ends in the loop being switched off to keep the guitarist in the pit happy!

[aidso]

If you could post the make and model of the induction loop amp it might help.

[seeingtrees]

Thank you for the additional replies. Hopefully this reply will also answer the suggestions made as well as updating on the situation.

 

We had an electrical engineer out this morning who also knew his stuff about electromagnetism. He came along with a bunch of machines that read signals and was able to trace the strength of electromagnetic and acoustic signals etc. In amongst his gadgets was a hand held for reading the strength of loop signal.

 

Conclusion after 2 hours of testing various combinations is that the signal I am picking up on the guitars and bass is that of the loop irrespective of whether the tv is on. It is the actual sound of what is going on within the neighbour's flat I am picking up via the loop when the tv isn't on. And then when the tv is on, without any volume on, this signal is then joined by the signal being beamed via the loop. As it is, the tv is on all day and all evening anyway.

 

Using the hand held loop signal reader and also my guitar, we tried not only different areas within my flat but also within the 5 storey building. With regards to my guitars themselves we even went through my little battery powered amp when checking round the block of flats but the signal didn't fade. No-where did the signal from her loop significantly reduce. The one source of a smile for me during all this process was the constant look of amazement on the engineer's face everytime we tried a new position to read and the signal was still there. He has been working as an electromagnetic and electrical engineer for 30 years and this is the first time he has come across this problem.

 

The final conclusion is the signal is being transmitted via all the steel in the building - especially the metal communal staircase and the (defunct) under floor heating mesh which is embedded in the fabric of the building and can't be removed. Oh and he checked my guitar/bass cables and my actual pickups and they are all shielded to an acceptable level.

 

Nothing we could do bar switching the entire loop system off made any difference. When the loop is off I am back to perfect sound and no interference.

 

Due to the severity of the neighbour's deafness and the safety requirement of her needing to be alerted to various sounds within her flat quite apart from the tv, the loop can not be switched off. Or at least it can physically be switched off but neither she nor the deaf charity want it switched off at any point.

 

She can't use any of the loop systems that beam direct source to source or ones that hang round her neck. In fact, in many years of experimenting in her previous flat (she's only just moved here) it was found that the only thing that worked was the loop.

 

At the end of the process I was left more or less with 'well that's life, sorry there is no more we can do about it'. So I am left without a solution beyond electromagnetically shielding one room so I can make music in it which is too expensive. I am very angry about this now.

 

And also really quite stunned. I've been happily living here for 15 years and out of the blue this happens. I should emphasize that it isn't a little bit of interference that one can just more or less ignore, but a significant amount.

 

It seems now the only solution is to sell my flat and move, or give up electric music.

[paulears]

It could be cheaper to buy a new guitar - unless it's a real favourite. The Line 6 modelling guitars shouldn't suffer from the loop as they don't have that kind of pickup? Probably not what you want, but a solution to the problem?

[seeingtrees]

It could be cheaper to buy a new guitar - unless it's a real favourite. The Line 6 modelling guitars shouldn't suffer from the loop as they don't have that kind of pickup? Probably not what you want, but a solution to the problem?

 

I've just been thinking of that very solution as much as it'd be expensive it is the cheapest solution. Maybe I'm picking you up on the loop!

 

I've been using fender strats and precisions for years but I'd be willing to change if it is the only real solution.

 

Do you think it'd make a significant difference?

[paulears]

Well, I have had a 6 string since they came out, and they seem immune to the usual lighting and sound buzzes. Guitar wise, I am very happy with it and I'd strongly advise you to try one out. The modelling quality is really, really good. Some of the presets you won't use, but I bought the programmer off eBay for forty quid and I've now got access to new tunings. I use Eb rather a lot as makes the sax players job loads eaiser. I even discovered that dropping the pitch of every string by octave is quite usable too! The footswitch has a balanced XLR out, so plugging into my studio mixer is a piece of cake. I've n reason to think the bass would be any less excellent - and the range of sounds will really impress you, I am confident. I never bought the bass because I have too many in my collection, and at the time I bought the 6 string because I needed a range of different guitar sounds.

[seeingtrees]

Well, I have had a 6 string since they came out, and they seem immune to the usual lighting and sound buzzes. Guitar wise, I am very happy with it and I'd strongly advise you to try one out. The modelling quality is really, really good. Some of the presets you won't use, but I bought the programmer off eBay for forty quid and I've now got access to new tunings. I use Eb rather a lot as makes the sax players job loads eaiser. I even discovered that dropping the pitch of every string by octave is quite usable too! The footswitch has a balanced XLR out, so plugging into my studio mixer is a piece of cake. I've n reason to think the bass would be any less excellent - and the range of sounds will really impress you, I am confident. I never bought the bass because I have too many in my collection, and at the time I bought the 6 string because I needed a range of different guitar sounds.

 

OK, thanks for that.

 

That all sounds very promising. I've had a wander around the internet reading various reviews and opinions on both the guitar and bass versions and it sounds worthwhile checking out. I've been using the various bass and guitar POD models as each new version comes out since 2000 and the bass one especially is exceptional so no reason to expect Line 6 won't be up to scratch with the physical versions of guitar and bass.

 

I also play tenor and soprano sax so an easy way to switch to new tunings using the add on looks good too.

 

Maybe this'll turn out to be some bizarre blessing in disguise, other than for my bank balance.

[thetechguru]

Hi again

 

I am very surprised at the outcome of this one! Normally steel in a building is a killer for induction loops especially mesh as in reinforced concrete etc.

 

Has your neighbour a loop system around the entire flat with an ambient microphone? If so how have they installed the loop cable and what type is it? Main reason for asking is I wouldn/t mind betting that somewhere on the 'earthy' side of the loop the cable is actually grounding via the building structure and thus turning the frame into a big loop. But for this to affect you so strongly would suggest the loop amplifier is driving so hard it will probably cook itself pretty soon so the problem will go away ( until it is repaired ). A simple test which could be done is to disconnect the loop cable from the amplifier and continuity check it and also check it to mains ground preferrably with a megger and not a multimeter.

 

A friend tells me that strats are notorious for poor shielding on the pick ups because of the single winding, you could change guitars etc etc but the problem is still the induction loop installation. Do you know who installed it? What will happen when the person next door needs a hearing aid and wants to listen to the telly!!!

[Simon Lewis]

I'm surprised about this too - having spent much time trying to overcome the effects of steel induced signal loss in loop installations. As suggested, could the manufacturer be contacted? If it's an Ampetronic unit, they have a particularly helpful technical department...

[Dmills]

I have a vague recollection that AFILS loops used to be classed as radio transmitters and required a license from the appropriate authorities, does anyone know if this is still the case?

If so, talking to Ofcom enforcement may be one possible route to getting the thing fixed.

 

I have a suspicion that the loop current is running waay too high, and could be turned down (and the hearing aid loop preamp turned up (Special software required, the hearing aid gain structure is a job for the local hearing aid specialists)).

 

The 'Nuclear' option is a modest stick welding set and a set of 30M arc cables (A few turns around the edge of the room * say 150A arc current), all of a sudden IR starts to look like a really good option....

 

Humbucking pickups on the guitars will really help, as will correctly screening the cavity.

A final thought, if you can get a sniff of the actual audio she is feeding to the loop, then some sort of quadrature loop at your level may get the signal level down to something workable, specialist design, but it may be possible.

 

Regards, Dan.

[Simon Lewis]

I have a vague recollection that AFILS loops used to be classed as radio transmitters and required a license from the appropriate authorities, does anyone know if this is still the case?

 

Not any more.

 

I have a suspicion that the loop current is running waay too high, and could be turned down (and the hearing aid loop preamp turned up (Special software required, the hearing aid gain structure is a job for the local hearing aid specialists)).

 

Loop current may well be too high, but the OP mentions that the user has had problems getting a system to be suitably loud. Modifying the hearing aid's telecoil gain would depend upon the helpfulness of the audiologist and the degree of adjustment available on the aid itself. Some of the NHS digital aids are pretty basic, having been built to a very low price....

One problem of making the telecoil output "hotter" might be problems with the level of background EMI and devices such as telephones - the change in level may be disconcerting, or even make the aid unusable..

 

Humbucking pickups on the guitars will really help, as will correctly screening the cavity.

 

That may well help, but I'd like to think that treating the source might be a better option!

 

A final thought, if you can get a sniff of the actual audio she is feeding to the loop, then some sort of quadrature loop at your level may get the signal level down to something workable, specialist design, but it may be possible.

 

A low spill design at the source would help, although this isn't as easy to do in the vertical plane. I do wonder if there is some blatant mistake in this system - like the earth of the ring main has been used as the loop conductor! There are some strange effects that can arise when the loop amp is plugged in some distance from the audio equipment it's connected to, with bunching of cables or (as mentioned above) unintentional grounding of the loop. It may be that the loop amp that being used is simply not designed for small domestic installations.

 

Simon