400 MHz Countermeasures? - Page 1
Forum section: electronics / rf-microwave

author: LRJ
author_rank: Contributor
timestamp: February 13, 2024, 10:53:15 pm
content: See image below of continuous stream of 397-434 MHz signals in my home (dBm between -67 and -73) measured with GQ EMF-390. Scanned everything in the house, basement & garage and nothing we have is emitting this. Note that RF activity is constant 24/7 and comprises the bulk of all RF readings. Intermittently, we have signals ~2400 for our WiFi and from those nearby and ~900 for our smart meter. Otherwise, it's a constant stream of 397-434.What are the potential countermeasures if this is either IR-UWB radar or an acoustic surveillance transmitter?

author: ahbushnell
author_rank: Frequent Contributor
timestamp: February 13, 2024, 11:18:43 pm
content: Tin hat

author: Andy Chee
author_rank: Super Contributor
timestamp: February 13, 2024, 11:20:21 pm
content: Quote from: LRJ on February 13, 2024, 10:53:15 pmIf these signals are continuous, then it shouldn't be hard to track down the source. You'll need a simple Yagi antenna, a signal attenuator, and read up on radio direction finding. Radio fox hunting resources will come in handy here.Basic procedure is to wave the Yagi around and add more attenuation, wave the Yagi around and locate the strongest signal, add a bit more attenuation. Keep doing this until you find a peak signal direction. Walk/drive in that direction and continue to add more attenuation bit by bit as you begin to narrow in on the signal source.My bet is a neighbour's wireless weather station.

author: LRJ
author_rank: Contributor
timestamp: February 13, 2024, 11:30:21 pm
content: There are broader issues I'm not going to get into that suggest nefarious neighbor activities. We didn't just see a signal and freak out. There's a lot more going on which preceded looking for various possibilities.So, I'd appreciate replies focused on countermeasures if radar or an acoustic transmitter are being used.

author: Andy Chee
author_rank: Super Contributor
timestamp: February 13, 2024, 11:33:51 pm
content: Quote from: LRJ on February 13, 2024, 11:30:21 pmFirst task is to locate the signal source. Forget about countermeasures until you have positively identified the source (at least a direction for the source anyway).

author: KE5FX
author_rank: Super Contributor
timestamp: February 13, 2024, 11:42:13 pm
content: Check your CO detectors, make sure they're working.Seriously. Check them. Now would be a good time. Forget about countermeasures until you've donethat.

author: coppercone2
author_rank: Super Contributor
timestamp: February 13, 2024, 11:49:23 pm
content: lol, this is the band used for any wireless gadget that you can find. Your counter measures are going to disrupt someones outdoor thermometer, wireless stereo transmitter, thinkgeek computer gadget, garage door, home security, flower pot telemetry, etc. Now it moved a bit to blutooth but you need to license that shit so its not always the best business decision.i think the counter measure you need is a Valium™read this because the only thing you are gonna do is probobly start a feudhttps://www.data-alliance.net/433mhz-antennas/most RF gadgets actually come with a 433Mhz antenna (like SDR) because its ubiquitous. BTW if you don't know already, ALOT of companies are getting into IOT now to offer smart functionality in devices. You will see this more and more.I see nothing wrong with trying to identify where a signal is coming from (this is learning about RF), but don't 'countermeasure' them like a idiot peon that thinks they found a witchalso the frequency output on that thing is probobly shit. We tested something like that and it was giving us random baloney, a MDO gave a clear answer.alsohttps://www.reddit.com/r/RTLSDR/comments/10417sz/will_43392mhz_and_423mhz_interfere_with_each_other/smart meters too.You'll have to answer to the electric and power company.I think your problem probobly falls under the realm of 'hicks talking shit'. The threat is when you walk on to your property line in slippers with a shotgun and a bottle when the cops show up. Every time there I have seen something with the property line there is someone holding a beverage on the other side talking nonsense

author: xrunner
author_rank: Super Contributor
timestamp: February 14, 2024, 12:45:17 am
content: Quote from: coppercone2 on February 13, 2024, 11:49:23 pmFor a long time (until I got my own wireless thermometer) I had an "atomic" clock that also had on the display an outside temperature indicator, but I didn't have any outside sending unit. It was just reading somebody else's signal. There are countless rf signals going into your house at the moment.I say just relax and enjoy modern gadgets.

author: coppercone2
author_rank: Super Contributor
timestamp: February 14, 2024, 01:18:43 am
content: do a blutooth scan in a apartment too easily 50 objects

author: cosmicray
author_rank: Frequent Contributor
timestamp: February 14, 2024, 01:37:07 am
content: OP, also keep in mind that Tire Pressure Monitoring transmitters (inside the tires) transmit around 433 MHz (for euro cars). It's a remote possibility, but keep that one in mind.

author: jonpaul
author_rank: Super Contributor
timestamp: February 14, 2024, 01:42:55 am
content: Analyzer? Antenna? Diagram of antenna vs property/may/house layout?j

author: coppercone2
author_rank: Super Contributor
timestamp: February 14, 2024, 03:05:57 am
content: in an effort to stop this, try walking around with your meter to make a signal strength map. With the tools you have the best you can probobly do is walk around and label on a map what the signal strengths are. It should only take a few hours to write down maybe 50 different positions.

author: radiolistener
author_rank: Super Contributor
timestamp: February 14, 2024, 03:52:44 am
content: you're needs to look on SDR receiver with FFT waterwall what type of signal you have.I have some wideband noise which cover entire VHF band and appears for 2-3 minutes. I think this is from some motor-driven kitchen equipment from neighbours, because I can listen analog motor noise in AM mode with motor slow-down pattern before it disappears. Most of all some kind of cheap Chinese cofee-machine without filters on it's motor.

author: Halcyon
author_rank: Unknown
timestamp: February 14, 2024, 04:29:04 am
content: Duplicate post.