Microwave Oven door attenuation in dB?

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Discussion Overview

The discussion revolves around the attenuation of microwave radiation by the door of a microwave oven (MWO) and concerns about potential leakage due to a slight gap in the door's fit. Participants explore methods to test the attenuation and discuss the implications of their findings.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes testing the microwave door's attenuation by measuring WiFi signal strength, noting a difference of about 33 dB between open and closed states.
  • Another participant suggests using a software-defined radio (SDR) as a sensitive method to test microwave leakage, referencing a demo where microwave signals from other units were detected.
  • Some participants propose that the door likely has a choke flange, indicating that the door gap may not be critical due to the fixed RF trap structure.
  • There is a general agreement among some participants that 33 dB attenuation seems reasonable based on the discussion.

Areas of Agreement / Disagreement

While some participants agree that 33 dB attenuation seems plausible, there is no consensus on the implications of the door gap or the best method for testing microwave leakage. Multiple viewpoints on the effectiveness of different testing methods remain.

Contextual Notes

The discussion does not resolve the potential implications of the observed attenuation or the adequacy of the testing methods proposed. Limitations in the measurements and assumptions about the door's design are acknowledged but not fully explored.

NTL2009
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I recently made a repair to the door switches/bracket on our microwave oven (MWO). All is well, but later, after reinstalling a trim piece and checking the fit, I noticed that with the door closed and latched, that there was a bit of play (1/8"?) - I could push the door a bit further closed, and it would spring back when I let go.

It probably was like this before and I just never noticed. But, I had some concern that it could be leaking. How to test this? My first step was a basic one, I took my phone, started a youtube video over WiFi (I made sure I was on the 2.4G WiFi band, which is close to the 2.45G MWO), turned the sound up, set it in the MWO, closed the door - and it kept playing.

If I opened the door and quickly looked at the WiFi antenna icon, it was at the lowest bar. Then I thought of a way to increase the information - I went into my router's admin page, and sure enough, it shows the signal strength of each wireless device. It indicated about -55 dBm with the door open, and about -88 dBm with the door closed. I had my wife push the door closed that last bit, and I maybe saw ~ 1 dB more attenuation. I repeated that with my tablet.

So I'm convinced the little bit of looseness on the door is no issue (it's probably acting as a wave-guide attenuator, rather than needing direct contact, and the length/width of any gap provides effective attenuation?). And with about 33 dB attenuation, a 1000 watt MWO would be below 1 watt total, in the range of a cell phone. So I think that is good, but the only specs I could find were rated in mW per cm^2.

Does 33dB attenuation seem right?
 
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A software designed radio (SDR) would be a great way to test it. Radios of course, are very sensitive.

I recall a SDR demo video (sorry, no link) that showed a man in an apartment building claiming to hear the noise of all the other tenant's microwave ovens turning on and off.
 

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