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Author Topic: How does my microwave affect my radio?  (Read 14665 times)

Offline Beaker

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How does my microwave affect my radio?
« on: 13/10/2009 09:30:05 »
Hi guys.

I have a spooky phenomenon happening every time I use my microwave. My Bug radio turns itself on every time the microwave starts and causes the microwave to make a nasty buzzing sound. Once I turn the radio off the noise stops. Just wondered how this is happening and hoping it's not caused by any leaking radiation! Can you help me?

Regards, Ellie from Bishops Stortford.

Ps congratulations on a fantastic show. I am working my way through every podcast you have made and have now been encouraged to learn more.

Which is the next science festival you will attend?


What do you think?
« Last Edit: 28/07/2010 11:18:00 by ellieanita »


 

Offline RD

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Re: How does my microwave affect my radio?
« Reply #1 on: 13/10/2009 13:23:48 »
Microwave oven could affect the radio, but not vice versa.
 

Offline techmind

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Re: How does my microwave affect my radio?
« Reply #2 on: 19/10/2009 20:24:30 »
Like RD, I would suggest you start by checking whether the "nasty buzzing sound" is really coming from the microwave oven itself, or whether it is coming from the radio when the oven is switched on. I would expect the latter to be more probable (although almost anything is possible!)

Are you operating the microwave correctly - if you turn on the microwave with nothing inside it or with a damaged door or with dirty door seals then it would not be surprising if microwave energy was leaking (and it could be enough to be dangerous).

How close is the radio (by 'Bug' radio I assume you mean the ET-like thing I find with a Google search?) to the microwave? If the radio is only affected when it's less than 20-30 centimetres from the door seal, I wouldn't be too surprised. If it happens at a greater distance then I'd be more worried.

Does the Bug radio also switch itself on if you operate (have a conversation or send a text message) a mobile phone (cellphone) eg less than 15cm from it? I have a couple of digital alarm clocks which malfunction with a phone very nearby.


The other possibility is that the radio is sensitive to interference carried down the mains electricty cable (I assume the radio has a mains adapter?). Can you run the radio on batteries and do you get the same symptoms?


Without a photograph or video, or answers to my questions above, I can't suggest much more.
 

Offline Beaker

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Re: How does my microwave affect my radio?
« Reply #3 on: 19/10/2009 22:30:41 »
Hi everyone, thanks so much for taking the time to reply to this bizarre occurrence.

The situation is this, said Bug radio is on top of microwave (see attached picture) and when I start the microwave to warm porridge for 2 minutes NOTHING happens....BUT,
When I run the microwave for longer you hear a clunk when (is it the magnetron?) kicks in for a power boost (say at around three minutes) and suddenly the radio turns on and the sound turns up loudly, the radio being on then causes interference with the microwave which in turn starts to make a worrying buzzing sound, remedied by quickly turning the radio off at speed as it sounds so bad!!
This clunking I'm referring to is prominent when you defrost something IE. when on defrost, the microwave goes clunk then it makes its normal sound, then after say 30 seconds it goes quieter, then after another 30 seconds it goes clunk and makes a normal sound for 30 then softer for 30 secs.

I don't know much about the workings of a mi cowave to know whats happening inside, but it's like the clunk signals a boost of power to the magnetron possibly??

So guys, am I in danger from leaking microwave radiation? Should I replace this microwave asap?

I REALLY appreciate you all taking the time to help me with this problem, some of you are seriously clever and I enjoy reading your responses so A BIG thank you to both of you!!

Kindest regards, ellie x
 

Offline Beaker

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Re: How does my microwave affect my radio?
« Reply #4 on: 19/10/2009 23:13:09 »
Hi Techmind,
 
I'm going to try a few of your suggested experiments over the next few days and let you know my findings.

I will cook a few Jacket spuds for a best results, not only do they require a longish time in the oven but I get to enjoy a nice treat while i muse over the problem.

I've taken to "not" standing near the oven whilst it's on if I can help it as I'm unsure of its safety now??

What damage can it be doing to me if radiation is leaking from it somehow? (I have been next to it for a few times you see)
Would I feel anything when standing nearby if it was leaking radiation, or would the damamge to my tissues no be felt at the time?

I have had this problem for a while so I hope I haven't caused myself any long term damage...
 [xx(]
 

Offline RD

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Re: How does my microwave affect my radio?
« Reply #5 on: 20/10/2009 04:12:33 »
I have had this problem for a while so I hope I haven't caused myself any long term damage...

The microwave radiation from the oven is not ionsing radiation like X-rays, e.g. Even if the oven it was leaking it would not increase your risk of cancer. If exposed to strong microwaves your flesh would heat up like meat in the oven.

Putting a radio directly on the microwave oven is not a good idea: you have put it in the 2nd worst place for interference from the oven, (1st worst being in the oven  :)).

I would relocate the "bug" radio further away from the oven to avoid any radio interference.

Microwave oven could affect the radio, but not vice versa.
I did not imagine that you had actually put the radio in contact with the oven. If the "bug" radio has a mains transformer or a magnet in its base, (e.g. loudspeaker or hard drive), then the magnetic field produced could interfere with the operation of the microwave oven ...

Quote
microwave oven safety rules ... 4. Never attach kitchen magnets to the microwave oven.
http://www.uen.org/Lessonplan/preview.cgi?LPid=3456
« Last Edit: 20/10/2009 07:02:53 by RD »
 

Offline Beaker

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Re: How does my microwave affect my radio?
« Reply #6 on: 20/10/2009 21:28:37 »
OH MY GOD OH MY GOD, I WISH I'D MOVED THE BUG RADIO AND FRIDGE MAGNETS BEFORE I READ YOUR POST...LOOK AT MY BLOWN UP MICROWAVE!

....erm.... I have to confess rather sheepishly that not only was I ignorant enough to put a radio on top of the microwave but I have also plastered the right side of the microwave with fridge magnets!!  :o

Thanks RD. You're like a Superhero saving me from myself...Do you wear a cape and tight underpants or is that too personal a question to ask?

I won't ask how you guessed I had possibly also used fridge magnets on it...(still hanging head in shame!) But thanks so much for all the advice!

ellie x

PS THE MICROWAVE PICTURE IS POSTED AS A JOKE, BUT I'M OFF TO REMOVE THE FRIDGE MAGNETS AND BUG RADIO NOW! LOL X
 

Offline techmind

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Re: How does my microwave affect my radio?
« Reply #7 on: 20/10/2009 22:43:37 »
With regard to the cluncking and buzzing of the microwave oven...

Normally the innards of a microwave (the magnetron which is the device that generates the microwave energy) operates either at full power (e.g. 750Watts) or completely off.
When you dial up a lower power ("defrost" is usually close to minimum) the microwave "simulates" the required power by switching on the magnetron for 10-15 seconds, then switching it off for 30 seconds or so. Averaged over the "on" time (which makes the louder buzzing) and the "off" time you get the average power you requested. So yes, literally the microwave transmitter (magnetron) is 'on' when you hear the louder buzz, and 'off' otherwise. If you use a higher power (closer to the full power of the oven) you should find that the 'off' periods get shorter compared to the 'on' periods.

A microwave oven, even in good condition, will always 'leak' a small amount of microwave energy, probably enough to detect with a fairly simple probe, but not enough to be harmful. The amount of leakage might be roughly equivalent to the power transmitted by a mobile phone handset in use.

The relatively small and safe amount of leaked microwave energy can still be enough to cause very nearby electronics to misbehave. That your radio sat right atop the microwave as shown in your photo misbehaves does not particularly surprise me.


This is a classic "EMC" (electromagnetic compatibility) issue. It is possible that your Bug radio is somewhat hyper-sensitive to microwaves. Interference issues depend on both how much energy the microwave is leaking AND how sensitive your radio is to that interference.


Without someone coming inspecting your microwave oven and testing it, none of us here can say for sure that your oven is safe.
From other experience, I can believe that it is possible that a 'safe' microwave could cause the interference you describe at the close proximity you show.
If the microwave caused your Bug radio to turn on when the Bug radio was more than 1 foot (30centimetres) away, and definitely if at more than 2 feet (60 centimetres) from the oven then I would be quite concerned and would strongly encourage you to get the microwave tested.

As a previous poster said, if the oven were leaking excessive microwave energy then that would tend to heat up anyone standing too close. The most susceptible parts of the body are generally reckoned to be the eyes (and probably the testicles for men) because of the lack of bloodflow to carry-away/redistribute the heat.


While I wouldn't recommend sticking fridge-magnets on the side of the microwave, the fact that they stick at all is indicative that the casing is steel, and that therefore the magnetic field probably isn't penetrating inside, so I don't think this too great a concern in practice.
Potentially I suppose the stronger magnets from a motor, possibly hard disk, or a speaker might be more of an issue with affecting the safe operation of the microwave - so it would be wise to move the radio away.
« Last Edit: 20/10/2009 22:53:05 by techmind »
 

Offline Beaker

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Re: How does my microwave affect my radio?
« Reply #8 on: 20/10/2009 22:56:19 »
Evening techmind!

That's a FANTASTIC reply, just what I was hoping for! A really knowledgeable answer too.

What a star you are for taking the time to write that lengthy reply.
 :D

It's actually a really powerful and excellent microwave, and pumps out a 1000W. I got it from Argos (along with breakdown cover)

So if I start to feel my eyes getting HOT and FIRM (thank God I don't personally have to apply that remark to the testicles comment!)I shall get it checked out!  he he he

 ;) ellie X
 

Offline FuzzyUK

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Re: How does my microwave affect my radio?
« Reply #9 on: 05/11/2009 18:49:57 »
My Bug radio turns itself on every time the microwave starts and causes the microwave to make a nasty buzzing sound. Once I turn the radio off the noise stops.

The microwaves generated by your cooker are being chopped on and off by nature of the magnetrons power supply which is derived from a rectified alternating 50 Hz mains supply. Because the supply is not 'pure' the pulsating DC has fairly fast rising edges and these produce sidebands of energy on the microwave source which can spill over into other areas of the radio spectrum, in this case as a 50 HZ annoying broadband rasp as picked up on your radio.

Domestic receivers such as an FM radio rarely have an external antenna connected to them in order to pull a good signal in and are thus very vulnerable to minute levels (micro watts) of interference from nearby equipment such as your microwave oven.

Your body will not fry with such low levels of leakage from the oven.
« Last Edit: 05/11/2009 19:04:31 by FuzzyUK »
 

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Re: How does my microwave affect my radio?
« Reply #9 on: 05/11/2009 18:49:57 »

 

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