I noticed this today when microwaving a lean cuisine. When i turn on the microwave to cook the food my wifi was shot down almost to nothing. When it turns off the WIFI goes back to normal.
Does anyone know why this happens and does it happen to you?

I've had a microwave interfere with SiriusXM radio, so pretty close?

I noticed this today when microwaving a lean cuisine. When i turn on the microwave to cook the food my wifi was shot down almost to nothing. When it turns off the WIFI goes back to normal.
Does anyone know why this happens and does it happen to you?

How old is your microwave? The question is, whether it has still the "old school" transformer or so,e lightweight inverter?
The thing is the microwave leakage from the oven does wipe out the Wifi all around, but the "old school" does that only in one mains halfwave and the WiFi protocol is designed to handle that (it squeezes into the other, "quiet" halfwaves).
But the HF inverter based designs operate at 10's kHz instead of the 50/60Hz, so the "quiet" time windows are getting too short for the Wifi, so it will collapse.
Anyway, the ITU designated the 2.4GHz as primarily for an energetic use, so the microwave ovens, lights or any other similar devices are the primary users of the band, so all the others have no guarantee to have the spectrum free enough (it is a stupidity of Sirius operators to use such band for an expensive to install satellite system) to have it available without disturbance.
Because it is "quite difficult" to disturb a microwave oven operation, so that spectra was freed for license free use (as it has no value for a serious communication use - beside the disturbance there are high transmission losses into any humidity in the air, because of the water molecular resonance; that is the main reason, why microwaves are operating there in the first place).

How old is your microwave? The question is, whether it has still the "old school" transformer or so,e lightweight inverter?
The thing is the microwave leakage from the oven does wipe out the Wifi all around, but the "old school" does that only in one mains halfwave and the WiFi protocol is designed to handle that (it squeezes into the other, "quiet" halfwaves).
But the HF inverter based designs operate at 10's kHz instead of the 50/60Hz, so the "quiet" time windows are getting too short for the Wifi, so it will collapse.
Anyway, the ITU designated the 2.4GHz as primarily for an energetic use, so the microwave ovens, lights or any other similar devices are the primary users of the band, so all the others have no guarantee to have the spectrum free enough (it is a stupidity of Sirius operators to use such band for an expensive to install satellite system) to have it available without disturbance.
Because it is "quite difficult" to disturb a microwave oven operation, so that spectra was freed for license free use (as it has no value for a serious communication use - beside the disturbance there are high transmission losses into any humidity in the air, because of the water molecular resonance; that is the main reason, why microwaves are operating there in the first place).

It's a GE JVM3160RFSS 30" Over-the-Range Microwave Oven in Stainless Steel and it gets used everyday, I don't know the HV source, but I think it's a transformer

We have never noticed that happening here, but then most of the kit we have are hard wired back to our patch panel by Ethernet.

We have never noticed that happening here, but then most of the kit we have are hard wired back to our patch panel by Ethernet.

And when we do use wi-fi (phones and Kindle only, and then rarely) we use 5GHz. I think microwave ovens use something near 2.4GHz so I'd expect possible problems on that band, although if you've got a decent oven it should really have better shielding.

What wi-fi band are you using..?

The only device that we have that only uses 2.4GHz is Kevin my Kindle. 

The only device that we have that only uses 2.4GHz is Kevin my Kindle.  

And we only need to connect it when downloading a new book, so no, it doesn't cause us any problems. Everything else that's likely to be in use when the microwave is in use is hard-wired.

How old is your microwave? The question is, whether it has still the "old school" transformer or so,e lightweight inverter?
The thing is the microwave leakage from the oven does wipe out the Wifi all around, but the "old school" does that only in one mains halfwave and the WiFi protocol is designed to handle that (it squeezes into the other, "quiet" halfwaves).
But the HF inverter based designs operate at 10's kHz instead of the 50/60Hz, so the "quiet" time windows are getting too short for the Wifi, so it will collapse.
Anyway, the ITU designated the 2.4GHz as primarily for an energetic use, so the microwave ovens, lights or any other similar devices are the primary users of the band, so all the others have no guarantee to have the spectrum free enough (it is a stupidity of Sirius operators to use such band for an expensive to install satellite system) to have it available without disturbance.
Because it is "quite difficult" to disturb a microwave oven operation, so that spectra was freed for license free use (as it has no value for a serious communication use - beside the disturbance there are high transmission losses into any humidity in the air, because of the water molecular resonance; that is the main reason, why microwaves are operating there in the first place).

@Medved: All microwaves sold here in Israel, are the magnetic transformer ones. I've only seen Panasonic Inverter microwave ovens appearing in the internet.

..., although if you've got a decent oven it should really have better shielding.

Even a quality shielding has quite significant leakage to wipe out communication on the same frequency.
The microwave shielding is designed to limit the leakage to safe limits, but can not suppress it below the natural noise floor on that spectrum. And because the radio communications mostly runs just a small bit above the noise floor (taking into account the S/N ratio the given system needs to function), the communication is the one who usually loose, so the disturbance (from the signal strength perspective) is inevitable.
It is the reason, why these energetic applications have their reserved frequencies/bands in the spectrum where these energetic applications are listed as the primary users, it is just technically not feasible to isolate kW (or for the industrial induction heating even MW) down to the background noise floor to not disturb any communication service on that frequencies and the same place.

@Medved: All microwaves sold here in Israel, are the magnetic transformer ones. I've only seen Panasonic Inverter microwave ovens appearing in the internet.

The high frequency inverter based designs are just a recent breed. It needed first the required components (mainly fast HV IGBTs and power resonance capacitors) to fall in prices to become competitive. On the other hand it allows the design of more compact and mainly lightweight microvave generator assembly (the magnetron plus its supply, where the transformer and the HV capacitors were big and heavy), so the same outer dimension format (the furniture standards became used to) may offer larger inner space and mainly higher and better regulated power (the inverter allows to regulate the magnetron power without the power pumping normally used).
Still it is a thing just for the newest and top end only products, the baseline still use the iron block, copper wire, aluminium foil and some foil...

I have just done a test with a Wi-Fi analyser app on my phone and didn't see any dip in signal strength when the microwave was on.

I have just done a test with a Wi-Fi analyser app on my phone and didn't see any dip in signal strength when the microwave was on.

The microwave does not influence the signal strength, the signal is still there, so the RSSI stays.
It just generate disturbance, so the receiver may not be able to extract the data.
Because WiFi design counts with the microwaves presence, the RSSI measurement is taken only when the signal is eligible for the receiver, so only in the "gaps" of the microwave generation.
The only consequence you may observe is some some drop in the average data rate you get from the connection. But this is influenced by way more variables, so it is difficult to distinguish in real life.

The microwave does not influence the signal strength, the signal is still there, so the RSSI stays.
It just generate disturbance, so the receiver may not be able to extract the data.
Because WiFi design counts with the microwaves presence, the RSSI measurement is taken only when the signal is eligible for the receiver, so only in the "gaps" of the microwave generation.
The only consequence you may observe is some some drop in the average data rate you get from the connection. But this is influenced by way more variables, so it is difficult to distinguish in real life.

Fair enough, I don't know as much of the technical side as I should. 

This used to happen to me when we had a really old microwave, the kind that has a stationary plate, a spinny propeller thing above the plate and woodgrain.

We presently have a typical Danby and no issue whatsoever

I would actually expect the modern microwaves to be more likely killing out the 2.4GHz band. The reason is, the tradditional magnetron supply designs feed the magnetron only in one half wave (8 or 10ms out of 16 or 20ms period), the other half-wave the current flows through a rectifier diode, so magnetron is quiet and so communication may take place. And all protocols used at 2.4GHz are designed for this type of band use (after all the energetic use, where the microwave ovens belong, are primary service the 2.4GHz band is reserved for by ITU; becuse it is obviously hard to cause any disturbance to ovens when using the same band for some communication, the 2.4GHz band was allocated as license free for digital communication as a secondary service).
It is only some recent microwave oven models, whose use a HF electronic inverter (usually operating in the 20..50kHz range on these power levels) instead of the bulky mains transformer, where the magnetron will actually radiate during both mains half waves (modulated just by the 20..50kHz HF but that is too short gaps for how the 2.4GHz communication protocols are designed).

So if there would be any problems from microwaves disturbing WiFi, BT or any other 2.4GHz protocol, it would more likely be some brand new oven and not any old one.