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

author: LRJ
author_rank: Contributor
timestamp: February 13, 2024, 10:59:56 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: moffy
author_rank: Super Contributor
timestamp: February 13, 2024, 11:05:00 pm
content: The 430MHz band is used by remotes, wireless weather station sensors etc, your levels are in the pico Watts not a problem.

author: LRJ
author_rank: Contributor
timestamp: February 13, 2024, 11:20:08 pm
content: Some radar and surveillance transmitters exhibit very low power levels as well. Not going into the broader circumstances, but there are other things going on that give us reason to believe one of these may be involved.Would appreciate replies focused only on what the best countermeasures would be if it is either radar or a surveillance transmitter. Thanks.

author: tggzzz
author_rank: Super Contributor
timestamp: February 13, 2024, 11:29:38 pm
content: Quote from: LRJ on February 13, 2024, 10:59:56 pmWhat is the instrument's noise floor? A reputable instrument will specify that.Failing that, take it into the middle of nowhere and see what the readings are.If worried about pW, cover your house in aluminium foil, and make sure it is very well grounded all the way around.

author: uer166
author_rank: Super Contributor
timestamp: February 14, 2024, 01:19:29 am
content: Quote from: LRJ on February 13, 2024, 11:20:08 pmWould be rad if you provided a specific example. ~400MHz is used by all kinds of things and the signal levels are very benign.

author: Bud
author_rank: Super Contributor
timestamp: February 14, 2024, 01:24:55 am
content: Do Not post same thing across multiple boards.As to what it is you measuring it is your handheld gizmo's noise floor.

author: CaptDon
author_rank: Super Contributor
timestamp: February 14, 2024, 02:02:49 am
content: I am starting to see a theme to your posts.

author: themadhippy
author_rank: Super Contributor
timestamp: February 14, 2024, 02:30:02 am
content: Quote

author: Kean
author_rank: Unknown
timestamp: February 14, 2024, 07:15:20 am
content: Seehttps://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=10353This level of readings on such devices is quite common as per the above linked post, and why they are generally used by (and marketed to) EMF/5G cranks to try drum up support amongst the less knowledgable (like lawmakers). As mentioned above, these are very low levels and are likely just the noise floor of a cheap receiver implementation. In any case you should expect lots of low level transmissions in populated areas on any of the license-free bands like 433MHz, 915MHz, 2.4GHz.I have to admit to buying a couple of devices like this many years ago (they were a bit simpler then), because they were cheap and as I was just learning RF I didn't really know better. Now when I see them sold by a company, I will seriously consider avoiding dealing with that company in general, even if they sell legitimate RF measurement devices.

author: ArdWar
author_rank: Frequent Contributor
timestamp: February 14, 2024, 07:35:15 am
content: Is there a specific reason why you singled out "IR-UWB radar" or is this just another "I read something on the internet so everything happening around me must be that thing at work"?Anyway noise floor aside, 433 MHz is ISM band. Therefore a *lot* of things use that particular band of frequency. From car keyfob, garage door opener, "smart" bulb, drone remote control, amateur radio, police CB radio, or even sometimes just some power supply leaking wideband noise.

author: Jeroen3
author_rank: Super Contributor
timestamp: February 14, 2024, 07:43:37 am
content: Time to get an RTL-SDR and see what it is then.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: February 14, 2024, 12:17:43 pm
content: Quote from: Jeroen3 on February 14, 2024, 07:43:37 amOr the more convenient to use, TinySA Ultra. This is a good specification hand held spectrum analyser covering up to 6 GHz that is excellent value for money. Only buy from approved sources, there are a lot of fakes around. See where to buy at:https://www.tinysa.org/wiki/Forget the toy EMF meters, I had the loan of a Tenmars TM-196 3-Axis RF Field Strength Meter... It looks the part, and even has a "calibration" menu setting, but went off the scale around the house for no obvious reason. I tried comparison measurements of a transmitter using the TM-196 alongside a half wave dipole and hand held spectrum analyser... The readings on the 196 were very unstable and "may" have been about right some of the time, but it just wasn't a stable reading you could rely on, by comparison the spectrum analyser reading was absolutely rock steady. These kinds of toy EMF meters are useless, leave them for the ghost huntersSJ

author: Kean
author_rank: Unknown
timestamp: February 14, 2024, 01:13:29 pm
content: Ah yes, the Tenmars TM-196... that brings back memories. I have one of those that I bought 12 or so years ago after seeing a similar (but much more expensive) unit being used by the local EMC lab for verifying field strength during immunity tests. It turned out to be not something you could rely on, just as you say. I saw comments from other owners complaining about the same issues. Amazingly many years later they are still available for sale.I now have multiple antennas and spectrum analysers, with my most recent acquisition being the TinySA Ultra which I really like for doing quick measurements.

author: Randy222
author_rank: Frequent Contributor
timestamp: February 14, 2024, 08:24:28 pm
content: I would buy a tinySA Ultra.But, those ~430's are at edge of 70cm ham band, so perhaps some harmonics?Why does the device show same freq multiple times? Does it ID a "channel" or tone on carrier?

author: bson
author_rank: Unknown
timestamp: February 14, 2024, 08:26:28 pm
content: Quote from: moffy on February 13, 2024, 11:05:00 pmAlso keyless car systems. (It's actually an ISM band.)

author: Shonky
author_rank: Frequent Contributor
timestamp: February 15, 2024, 05:42:55 am
content: IR-UWB is not going to have a peak at ~430MHz which as noted already is ISM and used for anything from doorbells, weather stations, garage remotes, car remotes etc.What makes you think it's IR-UWB anyway, because it appears you don't really understand what that even is?Those devices a specifically targetted at those whowantto find a problem rather than those who actuallyhavea problemSimilarly why do you think you have an "acoustic surveillance transmitter". Presumably that's an RF crank way of saying "bug"Take your device somewhere else and I suspect you'll see similar results. If you used it around the house and the values essentially didn't change, what do you think that means?Forget about "countermeasures" until you determine what you're even talking about (likely nothing)

author: nonlinearschool
author_rank: Contributor
timestamp: February 15, 2024, 06:20:24 am
content: That company has their own forum on their website. Why not ask the questions there? Sure you will get abundant suggestions and answers.

author: Shonky
author_rank: Frequent Contributor
timestamp: February 15, 2024, 06:50:53 am
content: Quote from: nonlinearschool on February 15, 2024, 06:20:24 amI had a quick look and yeah that forum is a special one for sure.

author: coromonadalix
author_rank: Super Contributor
timestamp: February 15, 2024, 01:07:34 pm
content: E.T go home ...

author: Randy222
author_rank: Frequent Contributor
timestamp: February 15, 2024, 04:41:26 pm
content: Quote from: Shonky on February 15, 2024, 05:42:55 amThe device itself uses a 430MHz crystal inside.But that is actually an ok test, just move the monitoring device to some other location and see if the 430MHz rolls off.If a bug, then maybe OP can research how 430MHz can be used to modulate against the microphones on devices inside the home. Maybe a havana syndrome case? I would think 10T would be more interesting in 2024.

author: LRJ
author_rank: Contributor
timestamp: February 15, 2024, 10:08:58 pm
content: I'm not an EMF crank. I'm not looking for a problem that isn't there. And, I'm not concerned about exposure to ~400 MHz in and of itself.The concern is a privacy / harassment concern as there are things happening that suggest someone is aware of our movements in the home & is using that information to engage in a sound / vibration harassment campaign. I can't engage local law enforcement (& haven't even tried) because the perpetrator turns it off when anyone comes to the house and it is often just below the city dB cutoffs anyway.Asked about countermeasures to see if I could employ something to interfere with anything providing location information to test to see if that disrupts the sound harassment efforts. Ultimately, I will need a professional assessment to pinpoint the exact source to take steps against the perpetrator.And I know exactly what IR-UWB radar is. 400 MHz is excellent for use through walls that aren't metal & there are a number of law enforcement and military use cases. It's even being evaluated for passive vital sign monitoring in health care.Here's an article for anyone who isn't aware that 400 MHz UWB radar exists:https://www.nature.com/articles/s41598-018-31669-y

author: LRJ
author_rank: Contributor
timestamp: February 15, 2024, 10:23:28 pm
content: That's just one isolated example. There's other more pedestrian, run of the mill low frequency noise.However, talked to a couple of sound / mechanical engineers who think any infrasound is likely coming as a vibration possibly coupled through the ground rather than through a speaker - obviously.

author: Gyro
author_rank: Super Contributor
timestamp: February 15, 2024, 10:25:08 pm
content: I don't think are on the right track in terms of somebody locating your position within your home. At 2-4Hz you would be looking out of the window and seeing somebody connecting an air duct or similar to your house. As such low frequencies (pressure variations) there's no way such effects would be localized to a particular room for instance...https://www.eevblog.com/forum/projects/infrasound-source/

author: LRJ
author_rank: Contributor
timestamp: February 15, 2024, 10:29:49 pm
content: When it comes to the infrasound, sure. But as I said in my most recent reply above, there is other more pedestrian noise being deployed (some low frequency, some just annoying). I'm not going to get into everything here but after weeks of this it's pretty clear to us.

author: coppercone2
author_rank: Super Contributor
timestamp: February 15, 2024, 10:30:13 pm
content: Like I said, make a frequency map and verify that the meter does not pick those signals up in a isolated environment.This should take approx a few hoursIf you have a frequency map, you can see where it gets stronger or weaker. This means draw a map and every say 6 feet record readings on a grid on all available space and see what it looks like for the different signals. Outside if you have a big property you need more reasonable distances but it should be a big grid with some resolution.You can't do anything more with a damn hand held thing like that.There is no point to trying to trick it out with antennas or whatever, Just make a damn map.A transmitter will present itself as a contour.

author: LRJ
author_rank: Contributor
timestamp: February 15, 2024, 10:40:06 pm
content: Agree - I also ordered a higher quality device & plan to implement your mapping strategy.

author: coppercone2
author_rank: Super Contributor
timestamp: February 15, 2024, 10:44:12 pm
content: well there is no magic bullet for this outside of expensive equipment that may or may not work (so a real bug sweeper team has a whole bunch of expensive shit) and pain staking stuff like mapping.the only way to expedite this is to hire pros

author: coppercone2
author_rank: Super Contributor
timestamp: February 15, 2024, 10:45:56 pm
content: if that meter you have is worth a damn (if its not picking up itself) then its perfectly fine for making a map with. Trying to do the same thing with a SA would be damn annoying unless you had a program to adjust it for you, so you might actually have a decent tool for the job when paired with a notepadwhat you can't trust it with is accuracy, but it might be consistent enough for the application, just make sure the battery stays above 40% for dodgy kit.

author: bson
author_rank: Unknown
timestamp: February 15, 2024, 11:00:26 pm
content: I would suggest it's all receiver LO leakage.Get a steel sheet and ground it to form a shield. It will throw an RF shadow. Then move it around the receiver to see if the levels change. Wherever the signal drops the most is the immediate direction. Long-range surveillance and weather radar is cyclic so will peak as the beam passes.I think you'll find it's nothing at all and totally unrelated to whatever noises you hear when alone.

author: tggzzz
author_rank: Super Contributor
timestamp: February 15, 2024, 11:08:04 pm
content: Quote from: coppercone2 on February 15, 2024, 10:45:56 pmThe OP is only interested in "evidence" that supports his own bizarre hypotheses. I doubt he understands the basic scientific tenet that hypotheses must befailsifiable, and tests must be able to have negative results.I strongly suspect that if the OP did as you suggest, then the negative result would be proof that "They" are "Controlling" the "Environment" to produce the negative result.

author: LRJ
author_rank: Contributor
timestamp: February 15, 2024, 11:25:21 pm
content: That's pretty funny as I formerly taught stats & research methods years ago.Seems like many folks on here have their own "hypothesis" that I'm some sort of crank or nut. I'm not, but those who need to pretend I am are free to spiral and sling insults.My expertise is not RF, mechanical or sound engineering so I got on the forum to try to connect with those who are to get some suggestions and perspectives. Appreciate those who actually tried to offer ideas and constructive feedback.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 15, 2024, 11:31:02 pm
content: I want to add to prior suggestions that no active countermeasures be deployed. I take no position on whether this is happening or not. But if it is happening it is illegal on several fronts. If you find solid evidence of it happening and can localize the source to any degree take the information to law enforcement (local police because it is harassment and possibly assault and the FCC because it violates those regulations (at any power level if there is intent to harm) and to a lawyer for possible civil action.Note that just detecting radiation of some form coming from the suspect location is insufficient, you must have evidence that it is directed at you and not merely the result of benign activity or evidence that it exceeds legally allowed radiated power in the mentioned bands. Several possibilities for benign activity have been mentioned on this thread and you can find the allowed power in various publications. Evidence that it exceeds allowed power will require some math to translate the received power back to the postulated source and will have to exceed the allowed value be enough to be certain that flaws in the calculation and measured received power are not the real source of the problem.While you can do shielding and other passive activities legally the minute you start doing active countermeasures you are just as bad as the possible perpetrator. Don't go there.

author: Randy222
author_rank: Frequent Contributor
timestamp: February 15, 2024, 11:46:33 pm
content: I will suggest this, on a serious side of the house.Buy a better tool. A tinySA Ultra, 10db SMA attenuator, and a decent 70cm-band SMA stick antenna, but can just use the included telescopic antenna that comes with the tinySA.1.5MHz was in my scope. Darm local 1550 AM pumping out lots of power not too far from me. Me and my tinySA were able to ID the source.To know what direction a signal comes from, need a better antenna than a simple omni. Corner and Yagi are gonna be BIG for 430MHz though. But, with omni antenna you can at least be very mobile with it to see if the 430MHz rolls off at some location beyond the home.Are there any Rf sensors in the home, like for alarm systems? My smoke/CO detector is Rf linked to the main alarm panel, as example.

author: LRJ
author_rank: Contributor
timestamp: February 16, 2024, 12:13:57 am
content: Agree & better tool is on the way.Will double-check regarding RF sensors but I don't think so.

author: Bud
author_rank: Super Contributor
timestamp: February 16, 2024, 02:10:53 am
content: Look for this type of vehicles parked near your house

author: uer166
author_rank: Super Contributor
timestamp: February 16, 2024, 03:29:08 am
content: If the issue is sound/vibration, sound like you need a good microphone and some FFT software, not RF!If you live in the city or close to infrastructure, weird stuff happens with HVAC, generator, railroad noise etc..Also check/replace your CO alarms.. I have personal experience with auditory hallucinations, and it's not fun!

author: LRJ
author_rank: Contributor
timestamp: February 16, 2024, 03:39:11 am
content: I have also connected with a local sound engineer. So I'm looking at that angle.Our CO alarms are relatively new and are fine. Readings are 0. It's not hallucinations.

author: Simon
author_rank: Unknown
timestamp: February 16, 2024, 07:42:53 am
content: Quote from: LRJ on February 15, 2024, 10:23:28 pmwhich means an even more powerful sound source that is even more unlikely. See a doctor.

author: Simon
author_rank: Unknown
timestamp: February 16, 2024, 07:44:53 am
content: ever heard of tinitus? most people know of it as ringing in the ear, I have had it as a low throbbing sound, for years I was convinced that a car was idling outside my house for very long periods when in fact although a car did my tinitus would then take over. Don't let it take you over.

author: LRJ
author_rank: Contributor
timestamp: February 16, 2024, 08:57:58 am
content: I know what tinnitus is but that’s not the cause as I’m not the only one perceiving the sounds / disturbances & it’s not happening when we’re in other locations.

author: tggzzz
author_rank: Super Contributor
timestamp: February 16, 2024, 10:19:09 am
content: Quote from: LRJ on February 15, 2024, 11:25:21 pmClearly you weren't taughtpracticalresearch methods.The first thing any scientist or engineer does is to find and understand the limitations of the techniques and equipment they are using.I previously noted there are no noise floor specifications for thethingyou are using. All reputable equipment will have that specification.Others have suggested you (1) repeat the measurements in the middle of nowhere, well away from any RF sources (including cellphones and wearable "health" gadgets) (2) plot a map of the measurements in and around your house, for different frequenciesDo those, report back,only thereafter is it worth discussing the measurements.

author: Randy222
author_rank: Frequent Contributor
timestamp: February 17, 2024, 01:48:13 am
content: I have a low power low freq item that bugs me mostly during summer months.To get direction I was looking at creating an amplifying horn. It's gonna be big.Some of the audio spectrum apps for Android devices work very well on mobile devices. That's one way to get ok freq spectrum with some dB values.430/433MHz is used for all sorts of home automation/IoT stuff. Neighbors using tech on 430/433 MHz (usually 433MHz) will carry a good distance. China sells all sorts of vid camera stuff using 430/433MHz, which yields constant stream on that freq, etc.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 17, 2024, 04:18:47 am
content: You don't need a large horn for low frequency audio, just widely spaced microphones. The concept is the same as the VLA telescope. With only two microphones you don't get the best accuracy, you may not need much. Same thing also applies for RF. Both wave bands require some math, but you can Google to get coursework and papers.

author: Simon
author_rank: Unknown
timestamp: February 17, 2024, 09:30:26 am
content: speakers make good low frequency microphones.

author: Randy222
author_rank: Frequent Contributor
timestamp: February 17, 2024, 08:21:59 pm
content: Quote from: Simon on February 17, 2024, 09:30:26 amOnly if the SPL is high enough. With low SPL the softness of the diaphram and even the surround can absorb the sound before coil starts to move.

author: Simon
author_rank: Unknown
timestamp: February 18, 2024, 07:53:27 am
content: well they will beat your smart phone mic for low frequencies.

author: Gyro
author_rank: Super Contributor
timestamp: February 18, 2024, 10:24:13 am
content: Actually, many small electret microphone capsules are flat down to 20Hz so it's likely that their response rolls off rather than brick walls below that. Such capsules can be used to make good free field measurement microphones. A speaker isn't going to pick up anything significant below its fundamental resonant frequency, which is likely to be in the 35-60Hz range.

author: MarkT
author_rank: Frequent Contributor
timestamp: February 18, 2024, 02:15:49 pm
content: Quote from: Randy222 on February 17, 2024, 08:21:59 pmNope, it should be quite linear at low amplitudes as solid friction isn't involved, there's no thresholding other than the noise floor.

author: Bud
author_rank: Super Contributor
timestamp: February 18, 2024, 04:04:57 pm
content: What i am missing is how the topic shifted from 433MHz to Audio

author: DavidAlfa
author_rank: Super Contributor
timestamp: February 18, 2024, 07:01:08 pm
content: With such power levels it's unlikely to come from your home.Baby monitor cameras, door bells.. 315/433/868MHz are everywhere.What's the target of this? Want some lead paint for your walls?

author: tggzzz
author_rank: Super Contributor
timestamp: February 18, 2024, 08:10:29 pm
content: Quote from: DavidAlfa on February 18, 2024, 07:01:08 pmMorelead is probably the last thing he needs.I will be happy to revise that suspicion after the OP has reported back with the noise floor measured in the middle of an empty field, and a map of the measurements in his "problematic" house.

author: DavidAlfa
author_rank: Super Contributor
timestamp: February 18, 2024, 08:56:23 pm
content: Hey! He might have a different problem...like cadmium or mercury

author: tggzzz
author_rank: Super Contributor
timestamp: February 18, 2024, 10:03:22 pm
content: Quote from: DavidAlfa on February 18, 2024, 08:56:23 pmWell, not too far from me has the highest levels of Cd in the soil in the UK, plus many Roman Pb workings. And my house water supply has Pb pipesOh. Perhaps I shouldn't have said that. Oops.

author: DavidAlfa
author_rank: Super Contributor
timestamp: February 18, 2024, 10:33:35 pm
content: Not a problem if water flows frequently, it's fairly worse to warm up (Acidic) wine in lead vessels! I'm trying to quit.

author: coppercone2
author_rank: Super Contributor
timestamp: February 18, 2024, 10:45:11 pm
content: you should just stick to the RF mapping for now because your connecting investigating two very seperate phenomena that are both hard to measure at the same time and its just dividing your effort into ending this as fast as possible because the critical part of the theory involves 1 being related to 2 and infrasound noise pollution is super common and random.

author: Randy222
author_rank: Frequent Contributor
timestamp: February 19, 2024, 06:55:56 pm
content: I would at least use the existing Rf monitoring devices to go outside and down the block to see if the 433MHz rolls off at all, just to test the device.Even if it's not accurate on dBm it can at least give indicator if the 433 is all over (like a radio station would be), or just high near a neighbors house or the like.There could even be someone keyed up on a 70cm repeater and stuck there, possibly 100mi away.

author: tggzzz
author_rank: Super Contributor
timestamp: February 19, 2024, 07:00:22 pm
content: Quote from: Randy222 on February 19, 2024, 06:55:56 pmYup.Not knowing the noise floor is a pretty basic omission!

author: pdenisowski
author_rank: Super Contributor
timestamp: February 19, 2024, 07:37:54 pm
content: Quote from: bson on February 14, 2024, 08:26:28 pmIn the United States automobile remotes are at ~315 MHz. There are (or rather, were) jammers that operated at this frequency, the idea being that you could prevent people from locking their car doors in public places and then steal from their car when they walked away and didn't notice they hadn't locked it. This actually happened more often than you might think, and it might have gone unnoticed even longer except that the 5th harmonic of 315 is 1575 - the GPS L1 frequency. Some car remote jammers also started affecting GPS reception and eventually the government started to take an interest. I haven't seen those kinds of jammers for many years now

author: pdenisowski
author_rank: Super Contributor
timestamp: February 19, 2024, 07:41:29 pm
content: Quote from: coppercone2 on February 15, 2024, 10:44:12 pmIndeed. The instruments I used when I did this were ... not inexpensive. Most people I knew who did this on a contract basis charged about 1-2K USD per day.But frankly, what would you do even if you found them? It's an ISM band and in the absence of a license holder suffering "harmful interference" the odds of a licensing authority like FCC getting involved is about zero.Source: I spent many years hunting down signals and interference in the field as part of my job

author: Simon
author_rank: Unknown
timestamp: February 19, 2024, 07:41:35 pm
content: All i know is I tried recording the racket my neighbor's made on my phone. Absolutely nothing came out, so I hooked up this old thing I found in the house when I moved in to my computer, it has a speaker as a mic and a headphone output, absolutely perfect.