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Topic Title: High Frequency Fluorescent light
Topic Summary: and interference
Created On: 15 April 2015 09:06 PM
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 21 April 2015 12:19 AM
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mapj1

Posts: 9366
Joined: 22 July 2004

I would be interesting to get to the bottom of the differences


may not help, here are some thoughts.

Photons are photons, but -
Black body radiation is 'white', well off-white, and contains photons of all energies, as its all thermal agitation that kicks them out, and its very well randomised indeed, and the spectrum is a continuum.

CFLs, and some kinds of white LED synthesise 'white' from a few phosphors with widely spaced colours, but the spectrum of energy is more of a comb than a continuum. Casually the eye can't tell the difference, but obviously colour rendering can be affected. I'm told dressmaking is easier in daylight, or colour corrected filament light. Though, as the sewing I do tends to be tent repair grade, and back cotton on green fabric is OK its not such an issue.

Actually if the light gets too single colour (laser like) then there can be weird dark spot effects as reflections may combine in a phase that cancels when seen from some angles - makes it look gritty - not normally an LED problem though.

A diffuse source like a florry tube will tend to fill in shadows making any dents in a textured surface less obvious (consider that dark craters on the moon would be filled in with extra suns from different angles..)
Also conventional gas discharge stuff, and LED supplies with inadequate smoothing tends to flicker at mains freq, and the fading time constants are not the same for all the phosphors, so the blue in the white may flicker more than the red.
Some folk apparently cant see this, in the way that they can't see the 25 frame count down in the title sequence of the BBC news properly, and didn't realise that's what it was, but others of us can, and find it quite annoying/ tiring.

I suspect there is also more to how the brain processes images than we understand - for example the flicker response is probably more pronounced when in danger - there are some odd experiments getting folk to read rapidly flashed messages while falling out of aeroplanes that seemed to show that many people can detect and read a rather shorter duration event when falling, than they can normally - as if the brain speeds up under stress - which it might.

Its probably an odd mix of physics and human physiology. And leather.

-------------------------
regards Mike
 21 April 2015 10:36 AM
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OMS

Posts: 22359
Joined: 23 March 2004

Originally posted by: stateit

I had an interesting chat with a customer trying to decide if EMF will be a 'deal breaker' on their prospective new 'dream home'.
It's adjacent to a hospital and the substaion is fairly near it. And in their reseach subsequent to this they discovered underground HV feeds run right past their house.
They were talking about lead shielding paint on walls, DC feeds for lighting and wired phone/data points to each room instead of wireless.
Some people take it very seriously... What they they want is the best environment for their young child. I'm waiting to see if they will buy the house once they've interpreted the results from their hired EMF meter. I kid you not.

[edit] Makes me wonder what self-inflicted radiation I live in [/edit]


Well, the power industry has been putting people into the proximity of increased magnetic fields for about 100 years now. There is no statistical evidence that the people suffer any adverse health effects beyond those they are statistically likley to suffer.

If your client is daft enough to spend money on EMF switches and all kinds of wierd surface coatings then fine - but it's simply tiger powder

Suggest they get a gauss meter - wander over to the sub and take a reading - then move about 1m and get another reading (they'll need to be in milligauss scale) - then try it at the house.

Then keep in mind that the hospital will have perhaps a 2.5 Tesla MRI scanner (or bigger) - and the RPA will be allowing a contour of about 5 Gauss (remember the milligauss we were measuring earlier) to escape from the room despite all the shielding - that comntour will extend some distance into transient areas, and less into permanently occupied areas (protection by time as well as dose)

Basically we live on a great big magnet - and we've evolved on that magnet

Regards

OMS

-------------------------
Let the wind blow you, across a big floor.
 21 April 2015 10:46 AM
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perspicacious

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What they they want is the best environment for their young child.

You mean that they won't be "permissive parents" and ban the child from sitting in front of a screen, having a mobile phone, using game controllers, using an electric blanket (you get the idea!) but simply only allow paper books?

Now I'm worried as surrounded by wiring in my office (other than the floor).......

Regards

BOD
 22 April 2015 10:00 PM
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stateit

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Originally posted by: OMS


Then keep in mind that the hospital will have perhaps a 2.5 Tesla MRI scanner (or bigger) - and the RPA will be allowing a contour of about 5 Gauss (remember the milligauss we were measuring earlier) to escape from the room despite all the shielding - that comntour will extend some distance into transient areas, and less into permanently occupied areas (protection by time as well as dose)


I know...

What they've worked out through their research is that the door handles in the hospital MRI rooms weigh several times as much as a normal door handle because they've got lead in them... >sigh<

I might ask them to read up about lead poisoning...

I did also ask them if they wore tinfoil hats, and they carried on talking to me. I think I attract them.

-------------------------
S George
http://www.sg-electrical.com
 23 April 2015 09:36 AM
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OMS

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LoL - my advice:

Turn smartly left, fall out and take great strides away from the nutters - don't go back (ever)

Regards

OMS

-------------------------
Let the wind blow you, across a big floor.
 23 April 2015 10:15 AM
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Jaymack

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Originally posted by: OMS
Well, the power industry has been putting people into the proximity of increased magnetic fields for about 100 years now. There is no statistical evidence that the people suffer any adverse health effects beyond those they are statistically likley to suffer.

Operators are subjected to magnetic fields in the cell rooms of aluminium smelters, all during their shifts and for many years. Care had to be exercised in manipulating the heavy iron bars, used for periodic stirring of the molten metal on cell surfaces for sampling, to avoid shorting the main busbars. This is not an environment for those with metal pins or plates in their bodies.

Interestingly, the smelter at Anglesey had their planned maintenance schedules on magnetic tape, until someone took them through the pot rooms.

Regards
 23 April 2015 10:39 AM
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OMS

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Totally agree Jaymack - people work in (sometimes) quite significant magnetic fields, pot smelters being a well known example- and a few precautions relating to ferrous material need to be taken.

I once saw a smart alec fire extinguisher service engineer wander into an MRI suite with a ferrous cannister, claiming we were being ripped off by a competitor because we were buying aluminium units - the look on his face when the extinguisher rose up and was nearly ripped from his grasp and the total bollocking he got from matron taught him a lesson about basic physics I suspect he hasn't forgotten in many a long year.

Did you ever work for Alcoa in the Swansea area out of interest - I recall you saying you had been at AWCO

Regards

OMS

-------------------------
Let the wind blow you, across a big floor.
 23 April 2015 03:19 PM
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Jaymack

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Originally posted by: OMS
Did you ever work for Alcoa in the Swansea area out of interest - I recall you saying you had been at AWCO

I just went down to AWCO for a few days, with some maintenance electricians in tow from the Invergordon smelter, to get some training on aluminium cable installation. I thought they were owned by the British Aluminium Company at that time.

Regards
 23 April 2015 04:06 PM
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OMS

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Ahhh OK - yes, BAC owned AWCO - I was ony dealing with them via Delta cables (summer job)

I put two and two together and made 5 there - I just wondered as a smelter man if you had been at the Waunarlwydd plant with Alcoa - as a very green engineer I did some HV/LV work there for both the smelter and the extrusion plant - on the same site was the (then) IMI titanium plant - resolving the HV inter ties was a real challenge as IMI operated at some very strange voltages if memory serves

regards

OMS

-------------------------
Let the wind blow you, across a big floor.
 23 April 2015 04:22 PM
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HarryJMacdonald

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There is certainly a lot of EMF radiation around! Many years ago I was working in the Middle East. One morning I was near a big (and I mean big, hook six foot across type big) crane. It had just lifted and dropped a load of cylinders. Dropped because the hook was hot enough to melt the rope. We were working about a mile from the largest Medium Wave transmitter in the Middle East and the RF energy had been picked up by the crane wire and heated the hook as it lay on the deck.
 04 May 2015 12:18 PM
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Zs

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Joined: 20 July 2006

Help!

Im gutted...I have a big interference issue.

At the moment this isn't audiophile snake-oil it's something anyone can hear because it shows on the radio (FM) as the same fuzzy noise you get when you need to re tune or move the antenna.

As far as I can tell it is when the monitors are switched on and/or when the Freesat box is on. Any combination causes it and the monitors can be (power) on without the computer connected for it to happen.

There are no fixed lights yet and I can tell you that a 1 watt ikea LED desk lamp causes horrible noise but that was only in there to give me some light to work and isn't staying in there. The rest of the lighting at the moment is tungsten halogen and it doesn't interfere with the radio.

The only cellotex is in the ceiling and floor and it has absolutely no cable through it. Everything is surface mounted. All cables are segregated in three compartment dado trunking so that means that all the power circuits are sharing the middle compartment and that TV and phone are in a separate section. Broadband doesn't go into the trunking it just pops through the wall and into the back of the computer.

I'm going to need the computer on at the same time as the modest recording I plan to do because I plan to be using Q base when the time comes.

Is interference on an FM radio a sign of other interferences?

Any ideas? I'm expecting the word filter to rear its head now but to be honest I know little about it.

I'll tell you about the success of the soundproofing on the other thread a bit later but that is a hit and I'm really pleased with it.

Edit: I also tested the second-hand Marshall Practice Amp and a new Vox mini amp,with the iPod through them and they don't cause any issues. Just the radio telling me something might not be right

thank you,

Zs

Edited: 04 May 2015 at 12:27 PM by Zs
 04 May 2015 03:29 PM
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weirdbeard

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Hi Zs what kind of radio are you using to observe the interference with, also does it stillinterfere with the recordings if you switch the radio off?

-------------------------
:beer)
 04 May 2015 04:14 PM
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stateit

Posts: 2668
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Hi Zs,

You may or may not wish to read the following line:

One type of 'filter' some recording studios use is a Faraday Cage. A bit extreme but possible... Search for 'faraday cage recording studio'



-------------------------
S George
http://www.sg-electrical.com
 04 May 2015 05:39 PM
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Zs

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A Faraday Cage? well that would take some doing!

It is an ordinary Roberts Radio. Running on battery it is fine and when I plug the mains in it all goes oingy-boingy.

I have wasted quite a bit of time on it this afternoon and have had to leave-off in favour of doing some essential certs and invoices. But I did separate all of the electrical circuits as far as I can by pulling them all from the dado trunking.

I've put a dedicated radial in for the music end of the proceedings but it is affected even on its own.

Maybe FM radio isn't a guide for interference and I'll get the power logger on it. But I'm so sad about this after all the effort. Oh well, the technical books on their new shelves look good.

Zs
 04 May 2015 06:06 PM
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mapj1

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Please don't frighten Zs George - nearly all interference problems can be solved without resorting to cages (*) At most a skeleton of carefully bonded shielding around a few key parts is enough. Unless we are designing an EMP bunker, which is a different matter, and much more

A wave around with the portable radio is always very good idea to get a feel for likely trouble sources - but remember that radio signals can be very weak - your PC may annihilate a signal limping in from afar that excites at the one or two micro-volt level on the antenna, and still be so weak it causes no trouble at all to the audio gear.
If it trashes the strongest local station even at ten yard range then I'd be a bit more worried, and then leads in and out of the offending unit may need the choking and filtering treatment - the aim is to allow the 50Hz through the power leads, and the audio through the audio, and as little else as possible.
In minor cases ferrite rings will raise the impedance to RF and lower the high frequency currents to an acceptable level (we normally like to drive things a factor of ten below 'minimum perceptible' if we can) and proper filtering and grounding strategies do the rest.

In some ways for audio its not VHF frequencies that are the usual problem, though some interference sources are very broadband and hit everything is sight.
You may be more representative listening with a MW or SW radio if you can get one- and the longer wavelength of the lower frequencies tend to be conducted out of one box into another, rather than radiated directly - so attacking the cables rather than the space room is the way to go.
keeping the clean and dirty wiring apart is the simplest strategy - so lighting cables and microphones not to share a duct..


*I'm not talking through my hat, - it's something of a family specialty in PJ land.... (I'm a second generation electronics and EMC type - "The radio amateurs guide to EMC "is my dads handiwork..)

-------------------------
regards Mike
 04 May 2015 06:56 PM
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John Peckham

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I have an amateur radio HF transceiver siting next to my computer and the house is full of electronic kit generating loads of RF interference.

The noise generated by all this electronic stuff can be heard when I switch on the transceiver and weak signals are drowned out by the noise. The transceiver has all sorts of clever stuff to overcome the noise but switching off the computer and other electronic kit has the biggest effect. Even switching off my electronic kit still does not silence the noise from my neighbors kit.

Mind you when I press the transmit button on my transceiver it does funny thing to my computer.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 04 May 2015 07:36 PM
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mapj1

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It is depressing but very true that nowadays nearly everything chucks out enough radiation to drown out weak signal reception, and filtering is often omitted from the cheaper 'China Export/ Fabricated Cheap in China' (CE/FCC marking fakes). Even on the stuff that passes, the pass/fail limits are not intended to protect weak signal reception, but will give a reasonable degree of protection to the neighbours and normal strength local broadcast signals. (Proper EMC standards like Def Stan Def Stan 59-411 have spurious radiation limits about 30dB lower... but that is another story.)
That said, a bag of ferrite cores and a sprinkling of suitable capacitance can work wonders, and many hams manage to combine extensive computer set-ups and weak signal HF reception, but I won't pretend it works straight out of the box in very many cases.
In Zs' case the threshold of pain is probably much higher than for you John, as the equipment will not be designed to act as a radio receiver and will therefore I would hope be quite a bit deafer than dedicated kit !
None the less it may be that the monitor power and video leads need some attention.

John, I presume you are aware of

http://rsgb.org/main/technical...cations-and-leaflets/

(you may think the PME leaflet needs updating, so do I...)

-------------------------
regards Mike
 04 May 2015 11:07 PM
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Zs

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Dubbele Nederlandse? Mapj1 your are very clever, I envy your knowledge.

OK, I'll change the power leads and check everything is good and tightly connected. That might be an issue as I bring the PC indoors every night so I might not be connecting it very well. Docking station required methinks.

I've only just put the TV cable in from the dish which is some 40 M away so I have just checked all the connections and they seem OK. the picture is perfect so I assume it's all connected well.

Then, were the radio signal bad, wouldn't that mean bad when running on battery as well as on mains? It's pretty good, well, normal, on battery. I trashed radio 2 and super-trashed radio 4 ( but R4 is compressed isn't it?).

Then some more; I've put four radial socket circuits in but we can discount the heating one because I've not connected it to the DB yet, so three. Each has an extra 2.5mm CPC alongside the twin and earth. One for music things, which is the longest, into which I plugged the radio. That is segregated from anything else. The other two are serving the computer and have loads of outlets plus a surge protection device each for the sensitive stuff. Any mileage in putting the entire PC/monitor/printer set up onto one circuit so that the whole lot belongs to the same circuit? I can't see that it would have a massive effect though, because earth and neutral bars are shared. But once downstream of the DB, could I have mucked it up by providing diversity and mixing the circuits?

I'll not be able to do anything more on it until next weekend but I could also 'TT' it (OMS gets cross with me for calling a rod a TT but you know what I mean). However, round here we are PME and are all quite close to each other so I think that I'd be wasting my time driving in stakes.

And oh, In order to bounce the available light I put up an arty row of mirrors opposite the window. Behind me when I am working so that I don't have to face the truth . Dave Z advised me of something called the 'flutter effect' a little while ago but we were discussing acoustics. I throw that into the mix in case something similar applies to radio or EMF interference.

Off to Google ferrite rings.

Thank you,

Zs
 05 May 2015 11:02 AM
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mapj1

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Zs, please check your PMs later tonight I'm writing a note for you that is turning into a short booklet and paid work is getting in the way. I'm sure you know the feeling.



-------------------------
regards Mike


Edited: 05 May 2015 at 05:33 PM by mapj1
 05 May 2015 11:18 AM
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John Peckham

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Zs

As Mike and I said all the electronic kit generates this RF noise to a greater or lesser extent. This RF energy is radiated from the kit in to the air directly and if mains wiring or other wiring (mouse, printer lead, monitor lead etc) is connected that just acts as an aerial to radiate even more noise. Your power logger won't be able to see this as it probably only goes up to the 50th harmonic, ish. You have find out that switching on your Ikea LED desk lamp is an RF noise generator. If you think that is bad wait until you fit and fire up your florescent lighting!

You said you have Celotex insulation. If this is the foil faced stuff then you have constructed a sort of Faraday cage but unfortunately you have your radio inside this along with your noise generators. To make things worse your nice friendly entertainment RF signal is being attenuated by the screening from the Celotex with the RF noise inside your cage now overwhelming the RF signal.

Winding the mains and other leads from your noise generators (computers etc) around ferrite rings (Rapid Electronics) will reduce the effectiveness of them to act as an aerial. Get the rings as close as you can to the input to the noise generators. Winding the mains lead of your radio around a ferrite ring will attenuate any mains bourne RF noise going in to your radio.

he noise is swamping your nice RF signal which is being screened out by the Celotex. You need to improve your signal to noise ratio (S/N ratio). Decreasing the noise with the ferrite rings will help but also an external aerial for the radio will pay dividends. An external FM aerial outside, the higher the better, and a coax feed in to your radio as short as possible should make a big difference. An earth electrode connected to your mains earth will help a bit but not hugely.

Out of interest did you wire the sockets in a ring? As putting your noise generators inside a ring is much worse for mains borne EMC than radials.

By the way the laws of nature determine that men have sheds and workshops, women have studios! If a women ever put a Myford lathe or a pillar drill in to her studio the world would tilt on it's axis and permanent darkness would descend on the earth at it would be the end of mankind.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
IET » Wiring and the regulations » High Frequency Fluorescent light

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