Dexcom sensor restarts: microwave trick and 2-hour restart

Saw this video and was very interested in trying this:


Inventive way to get a Faraday cage!

Why the microwave? Is there a specific reason such as microwave preventing communication or something? I’d be afraid someone would accidentally turn the microwave on (even with the sticker) and ruining the receiver.

What I noticed…

The video starts with a time of “9:02 PM” on the iPhone and a time of “9:01 PM” on the receiver (which can be seen at 3 seconds in the video)

After she puts the receiver in the microwave and waits 2 hours (actually, she says more like 2 hours 23 minutes)…the time on the iPhone should have read “11:25 PM”…instead, it reads “8:41 PM”. Hmmm…I smell something fishy.

You’ll also notice that after she switches her receiver back on, the time now reads “8:40 PM”…Whaaaaa?

The very end of the video (when both devices are being calibrated), the devices read “8:51 PM”.

I smell BS, but someone’s welcome to test it and report back. :stuck_out_tongue: I’m not willing to potentially screw up a session trying this. If the times matched up, heck yeah…but with the times being off like that, I smell something very fishy.

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the person who posted it is very active in #wearenotwaiting so I doubt it’s a scam – could be she has some wonky receiver possibly. We’ll try next time and report back.
I think it also works if you just take it completely out of range for two hours.

Wasn’t just the receiver…the phone also had wrong times. I’ve asked on her video…waiting to hear back. I’m suspicious anytime someone is making a video where time should flow one way, but it doesn’t.

haha, yes, completely defying the arrow of time should be a red flag :laughing:


She did not explain it very well. But yes, it’s just a signal blocker. Might be safer to put it outside in your car!

I had thought about doing something like this a while ago, but I wasn’t really all that invested in it. Just to get readings for 2 hours, it didn’t seem worth the hassle to me.


Microwave blasts whatever you put into the oven with radio waves in a specific frequency band. For obvious safety reasons it is designed to shield the environment (and people) around it from these radio waves. Bluetooth radio, which is used by G5, operates in exactly the same frequency band, which is why a microwave oven is an excellent shield to prevent comms between a G5 transmitter and a G5 receiver, and that’s the main point in the procedure described in that video.

Now, why do microwaves and bluetooth (as well as wi-fi and bunch of other useful radio stuff) operate in that same frequency band? This is because certain bands in the radio spectrum have been left unlicensed, which means “free” for industrial, scientific, and medical (ISM) uses (as opposed to licensed radio or TV for example). Years ago, microwaves were placed into one of these ISM bands (specifically around 2,450 MHz). Much later, the same band was found well suited for wi-fi, bluetooth and such.

Finally, regarding legitimacy of the video: I’m 100% sure this is perfectly legitimate and true. The author of the video is one of the most prolific and respected contributors in the DIY community. Many people have successfully reproduced the experiment (just do not turn on the microwave!) The time anomaly in the video might be due to some video editing issues, do not know.


Thanks for the awesome explanation! Time thing is still fishy, though…I’ll wait for someone I TRUST (you guys/gals) to test it before I will, though.

My pleasure - after many years in DOC, I finally get to write something I actually know :slight_smile: Regarding the test: unfortunately, I am still using G4 so I am not able to personally confirm the experiment but I have no doubts it would be successful.


I cooked it for about 2 min on high. Is this too long?


Okay, the boss has spoken. @ErinElizabeth said she’d be willing to try it (according to her, there doesn’t appear to be any harm in trying it) so it looks like we’ll be testing this out next time. I’ll report back on whether we had the same results or not .


Let us know if time jumps back two and a half hours as well!


Somehow I don’t think that’ll happen but maybe this experiment opens a wormhole or results in teleportation.


It’s also been confirmed that a “Faraday bag” ($9 on Amazon) works just as well. Or, at $0 cost and with minimal (but not zero!) risks of opening a time-warp wormhole, just taking the receiver far enough from the transmitter would suffice.


will def. test it next time it’s sensor restart…will keep everyone posted.


Nobody here has actually stated the technique, so here it is. The person in the video has a phone receiving BG data via the normal Dex app. They turn on a Dex receiver and wait about 10 minutes for 2 BG values to appear on the receiver. Immediately after the second BG value comes into the receiver, on the receiver do the stop sensor, start sensor thing. Immediately thereafter take measures to prevent the receiver from communicating with the transmitter during the next broadcast (which is now about 3 minutes in the future.) and keep the receiver out of communication during the entire warmup. The phone will continue to receive BG data, the transmitter now thinks it is in the 2-hour warmup, and the Dex receiver has “lost signal.” After 2 hours+, maybe 2 1/2 hours just to be safe, bring the Dex receiver back into communication range. It will show that it is within 5 minutes of completing the warmup. Within 5 minutes the receiver will say that the warmup wait is over. At that time, you can shut down the receiver and use the phone to calibrate. No gap in the BG data on the phone. Which I think is huge for looping, and great in any case.


Can you do this right when the receiver prompts for a sensor restart? or do you need to do this 2 hours beforehand so that the phone will continue to receive data?

Nice write-up.

This entire approach is actually a nifty loophole when the microwave is removed from the mix (which otherwise makes this look gimmicky).

Putting the receiver outside in the car (for the duration of the 2-hr warmup) is a reasonable location.

A sensor can be restarted anytime anybody wants as long as it does not exceed 7 days (to the minute). Often times I find it more convenient to restart a sensor on day #6 which allows it to easily fit into whatever our schedule happens to be. There is nothing about this approach which would restrict the ability to do a preemptive sensor restart.