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A Beginner's Two-Component Crystal-Style Wi-Fi Detector
- jqpabc123 9mo agoCan this be used to detect radiation escaping a microwave oven? A friend of mine has a microwave that noticeably degrades his wifi when it is in use.
- zxexz 9mo agoSounds like he’s in need of a new microwave. Not tongue-in-cheek; sounds like there’s something up with the shielding, and if it’s not visible, how will you know if it gets worse? Edit: I see no reason this wouldn’t work, however?
- jeffbee 9mo agoThere is not substantial variance from one microwave to the next. They are all made by one outfit, then dressed up in different superficial brands and priced randomly. The emissions of a microwave oven are regulated by the FDA, not the FCC.
- macintux 9mo agoThat doesn't mean, however, that an aging appliance can't misbehave.
- bgbntty2 9mo agoI've tested a few microwaves from different manufacturers with my phone a few years ago. I think I looked at some file in my router (OpenWRT), but I can't recall. I got a lot of dropped packets each time. The amount of degradation was similar for the different microwaves. I had to put the phone close to the microwave to detect this. The degradation was obviously stronger when the phone was closer. If your friend experiences noticeable degradation regardless of the distance within the room, it might be worrisome. But I think it's normal to have some interference. That doesn't necessarily mean enough of the 2.4 GHz radiation escapes the microwave to be harmful to an animal, as Wi-Fi, Bluetooth and so on are very weak, comparatively. Funny thing is, after putting my phone inside a closed turned off microwave, it got Wi-Fi, although very weak. I didn't try that with all the microwaves, but with 2 or 3 of them. I think the Faraday cage around the microwave was built to be good enough for safety, but it wasn't built with Wi-Fi interference in mind. Disclaimer: I might be wrong, as I don't have enough background to make any bold claims.
- avidiax 9mo ago> If your friend experiences noticeable degradation regardless of the distance within the room, it might be worrisome. Probably not. I recall calculating it once, and the legal requirements for microwave oven shielding still allow it to produce a few watts of 2.4Ghz leakage. This is contrasted to 50mW typical WiFi AP power, and 5-50mW BlueTooth powers. A few watts is totally non-dangerous to humans, especially diffused across the entire door.
- shibapuppie 9mo agoAn old Unifi disc AP will do 100mw or 20dbm out of the box, a few cheap Cudy APs I have do about 400mw or about 26dbm. On 2.4 GHz in the US you're allowed up to 36dbm, 30 of that can be transmitter, the remaining 6 can be a higher gain antenna.
- bcook 9mo agoFor devices where connectivity is more important, switch them from 2.4Ghz to 5Ghz to avoid microwave interference.
- nja 9mo agoOther than phones and laptops (i.e. "real computers"), most devices only support 2.4, no? I can't recall the last time I set up a non-computer device that didn't say "make sure you're using a 2.4GHz network"... (I imagine it's a much lower cost to only handle 2.4GHz?)
- tzs 9mo agoI was curious so checked my network. I've got 21 things on 2.4 and 16 things on 5. The 16 are 4 computers (2 Macs, a Surface Pro 4, and an RPi 4), 3 mobile devices (iPhone, iPad, Apple Watch), 3 media devices (Fire TV, Nintendo Switch, and Kindle Oasis), one smart plug, a Brother printer, 3 smart speakers (Google Home Mini, two Echos), and an EV charger.
- tgv 9mo agoThe article says: "responds to [...] microwave oven leakage".
- KaiserPro 9mo agoYou could subsitute the LED for a moving coil meter: https://www.codrey.com/electrical/moving-coil-meter/ https://www.codrey.com/electrical/moving-coil-meter/ They have am much lower current and voltage requirement, so might me more sensitive. You can also do tuning to use different sized antenna. However that strays into analogue eletronics, which I've not really touched for 15 years.
- jeffbee 9mo agoMicrowaves degrade everyone's 2.4 GHz ISM band radios. Wi-Fi occupies the ISM band because it's a garbage band that was already wrecked by this type of equipment. There isn't a solution to this; the safe leakage from a microwave oven is millions of times more powerful than wifi field strength. 5 or 6GHz band avoids the problem.
- georgefrowny 9mo agoThere is a solution. Spread-spectrum methods for digging out signals from deep in the noise floor. It's just maths, but the amount of noise you can reject that way is really nuts.
- pwg 9mo agoFrom the fine article, second paragraph: "you can build a tiny “crystal detector” that responds to 2.4 GHz Wi-Fi, Bluetooth, and even microwave oven leakage"
- pseudohadamard 9mo agoIf they're seriously concerned, you can get microwave leak detectors for very little money from most crapvendors. The problem with this design is that while it's a cool toy it'll be prone to false negatives...
- thenthenthen 9mo agoI made hundreds of these. Never worked
- ides_dev 9mo agoHundreds? Really? I can see making two or three before giving up, but to build hundreds..
- BugsJustFindMe 9mo agoEspecially if they never worked.
- thenthenthen 9mo agoI never give up. Tried soo many different diodes, but the ‘good’ ones seem very susceptible to clones/fakes since they arent manufactured anymore. There is a company that makes dedicated IC’s that can harvest the emf very efficiently, bit expensive though… and a black box..
- ifh-hn 9mo agoSo the question is how to do similar for 5ghz?
- avidiax 9mo agoFaster diode, like HSMS-2850 [1], and different leg lengths (tune for 5Ghz). [1] https://datasheet4u.com/pdf-down/H/S/M/HSMS-2862_AgilentTechnologies.pdf https://datasheet4u.com/pdf-down/H/S/M/HSMS-2862_AgilentTech...
- ifh-hn 9mo agoThanks. Appreciate the reply. From a brief look that might detect 2.4ghz too? Really wish I was clever enough to do electronics!
- avidiax 9mo agoDepends on the length of the antenna. I'd bet you can get a length close enough to be a quarter-wave 5Ghz and 1/2-wave 2.4ghz antenna. Just buy a 2.4/5Ghz combo antenna and slap the diodes across it.
- ifh-hn 9mo agoI love simple solution like this. It'd be cool just wandering around being able to detect mobile and stuff with a tiny led. This sort of thing is definitely why I come the HN.
- didntknowyou 9mo agocurious, so if you build a "wall" of these, it would use up the wiress energy in the air so will absorb the excess waves around you?
- thenthenthen 9mo agoDepends if you are standing infront or behind the wall ;)
- orbital-decay 9mo agoOf course. Ambient radiation is a viable power source for distributed sensor networks and similar low-power stuff. https://en.wikipedia.org/wiki/Energy_harvesting https://en.wikipedia.org/wiki/Energy_harvesting
- cluckindan 9mo agoAn array of these would also allow you to better discover individual sources in a room with lots of devices.
- deleted 9mo ago[deleted]
- wowczarek 9mo agoRemember those little LED keychains for your "mobile phone" that would magically light up when taking/making calls and sending/receiving texts?
- thenthenthen 9mo agoThese stopped working since 2G, since it uses radically less power. Altho I did recall seeing some fancy phone cases with blinkies on 3G… never could replicate it sadly. I guess with a lot of joule thief/stepup circuits it might work…
- zoklet-enjoyer 9mo agoI don't remember that, but I do remember my speakers buzzing just before a call or text came through.
- b00ty4breakfast 9mo agothey still do that, but I think that this is RFI from the processor rather than a deliberate rf transmission
- zoklet-enjoyer 9mo agoI haven't heard it in years, since around the time of the song your username references
- pavlus 9mo agoThis is how FPV jammers are often field-checked in Russo-Ukrainian war. It doesn't test frequencies or spectrum quality, but is a useful indicator, that jammer is actually emitting (has power and is turned on), so you can be sure, that if it's up to spec and covers frequently used frequencies at your location - it actually tries to do it's job, instead of being a costly paperweight.
- peter_d_sherman 9mo ago>"Using just two components — a high-speed [1N5711] Schottky diode and an LED — you can build a tiny “crystal detector” that responds to 2.4 GHz Wi-Fi, Bluetooth, and even microwave..." That is interesting! I never knew that a Schottky diode could rectify at 2.4 GHz -- that's pretty darn impressive!