SDR: Noise from Powerline? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 26, 2018, 03:55:51 pm
content: So with my SDR I try to get some Shortwave Radio. I just get the huge noise and dont know where the come from?!Does anyone know if the come from Powerline?I remove everything from the Power in the Room and the are still there.

author: KD4PBS
author_rank: Contributor
timestamp: March 26, 2018, 05:25:28 pm
content: It's most likely all the little birdies and whistles from the computer that is running the SDR, as well as the electronics within the SDR itself. Could also be any of a number of other people in your neighborhood with offending noisemakers such as LED lights, CFL lights, "awesome" computers with LED lights inside and a huge hole in the side with a transparent plastic window covering that hole. Generally speaking, most of the electronic crap made today (mostly from far Eastern countries) will make this kind of broadband noise indiscriminately.Remove the antenna and replace it with something small and perhaps you'll at least be able to narrow down the stuff in your own vicinity that is creating this trash.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 26, 2018, 05:30:49 pm
content: I life in an House and the Antenna is outside on the Window. And I use an Pc and Laptop. On both Device the same noise (sure the PC was plugged of). The only thing who was not plugged of was me UPS who was turn off.Maybe I ask me Dad what he is pluged in the house. Maybe someone see that noise before.

author: Emo
author_rank: Regular Contributor
timestamp: March 26, 2018, 06:06:37 pm
content: Hi,If you live in an area with DSL services this will represent the carriers used. Especially in combination with overhead lines the level can be very high. Virtually eliminating all MW and SW reception.

author: KD4PBS
author_rank: Contributor
timestamp: March 26, 2018, 09:09:11 pm
content: So, the antenna is within a few tens of meters of the SDR and the PC or laptop? Is within a few tens of meters of other dwellings as well, or are you out in the middle of farmland where there are no other homes for several hundreds or thousands of meters? You have to realize that HF radio can be very fragile with noise. I listed several potential sources in my first post, Emo added to that. Making sure all ofyourpossible sources are turned off is only part of the equation - your neighbors could have potentially hundreds of these as well, creating a veritable cesspool of interference to the whole HF band.Also, if this is a cheap little RTLSDR type SDR, then expect it to perform rather poorly at these frequencies anyway. If it is a high-end SDR type transceiver which is designed to be a low-noise device at these frequencies, then at least you can probably eliminate the actual SDR as being the generator of this noise.The size of the antenna might also help eliminate some of the offending noise by giving you more of the desired signal and less of the undesired.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 27, 2018, 11:04:29 pm
content: QuoteSure. But I never had that strong Signals.QuoteThe Antenna is outside and 2m away from my Pc but the dont create an noise.QuoteYes it seem i h have to call the Authorities.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 27, 2018, 11:08:52 pm
content: QuoteSure. But I never had that strong Signals.QuoteThe Antenna is outside and 2m away from my Pc but the dont create an noise.QuoteYes it seem i h have to call the Authorities.

author: KD4PBS
author_rank: Contributor
timestamp: March 28, 2018, 02:17:33 pm
content: I've never known a PC that doesn't create noise somewhere in some way. I mean, I'm sure they exist, but it's not likely that a consumer would have it.As a whole, it's not an issue when you're 50-100 meters away from the antenna, but an antenna that is 2 meters away from a computer would be something I would suspect as being damaged if it didn't pick up interference in the HF band.How about grabbing a real HF radio - something portable and something that uses tuned RF circuits rather than an SDR, and hooking it up to this same antenna. Switch everything else off and see if it still picks up this interference. An old AM radio would even work in this instance. Does your car have an AM radio? What does it sound like?

author: phenol
author_rank: Regular Contributor
timestamp: March 28, 2018, 02:42:29 pm
content: i dug out my home brew sw receiver a while back and figured i should give the dial a spin or two with a simple wire hanging out the window. Needless to say, there was horrendous noise all across the sw bands, a little less on 10m. The thing has heavy band pass filtering a la PA3AKE with sizable toroids...I found that the worst offenders inside the house are the TVs and the satellite receivers with their power supply bricks. Much less so my laptop.They spew noise well into UHF bands. The 2m band is unusable with a rubber duck antenna. The wifi router is another offender. I resorted to wrapping the router with Al foil (no effect) and clamping ferrites onto the LAN cable right behind the router. This did reduce garbage by couple of db on VHF/UHF.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 28, 2018, 03:05:00 pm
content: Quote from: KD4PBS on March 28, 2018, 02:17:33 pmI don't notice an objectionable amount of noise from my PC (regular brand name PSU, I forget which one), and that was testing with sniffer probes around the power cord. Only loud appliances I've noticed are my own creations (which I've since shielded or snubbed down to similar levels).Instruments include a 40m SW radio (comparing against receiver noise floor) and speccy.In this area, I seem to have diverse sources in similar frequency ranges, none of them attributable to my own equipment.Tim

author: KD4PBS
author_rank: Contributor
timestamp: March 28, 2018, 06:31:44 pm
content: Interesting.I've always been able to find something somewhere when sniffing around the near-field of every computer I've ever probed with a small loop hooked to a SpecAn. Of course, it's not like I've testedhundreds. More likeseveral.They are certainly better than they used to be, but they're not silent by any stretch of the imagination.Add that to the fact that these RTLSDR things are powered and controlled directly by a noisy USB connection, and one has a recipe for what the OP sees. I certainly noticed similar behavior when I played with the RTLSDR. They're usable at higher frequencies, but certainly not at HF.And then there's those few HF radios that areonlycontrollable by a computer; eg. the TS-B2000. Man, what a mistake that one was!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 28, 2018, 07:09:20 pm
content: Mind, I haven't, like, gone through with a LISN and audited everything -- the gain of a near field probe is pitiful, so it could very well be chuffing out significant noise (as in, well above noise floor for the optimal setup). But I suspect it's close to, or below, the FCC limit at least, as it should be, and that doesn't seem to greatly impact the shortwave conditions around here, relative to atmospheric and/or other ambient noise.Tim

author: CopperCone
author_rank: Super Contributor
timestamp: March 28, 2018, 08:20:17 pm
content: The thing I used is a pickup coil designed for RPM measurement etc, I hooked it up with shielded 4 conductor cable, 2 wires per pin, with the shield of the cable connected to the shield of the pickup coil.I hooked up the pickup coil with a bandwidth of 50KHz to two preamp/filter boxes (wavetek) with I believe 80dB gain total and you can defiantly pick alot of shit up near computers, especially if you sniff near the ports on the metallic shield areas. You pick up audio frequency growling and stuff, and when hooked into a SA there is stuff above audio too. Filter boxes are nice because if you have two, you can easily put a 4th order highpass filter at 150Hz to eliminate power line noise from the audio.May have been 120dB gain (I think I might have hooked up my 100KHz bandwidth LT1028 based filter first? it has 2 20dB gain stages IIRC.If you want to find stuff, I found the e-field probes are very good at it, to high bandwidths. I made one by drilling a hole in a steel ball (removed from a fence post) and soldering it to the inner pin of a BNC connector, then epoxying a support around it made of old PVC pipe cut in half. Then coating the ball with epoxy. Much easier to get a signal near stuff like cables etc then with a magnetic loop probe.Then your next best bet is to make the square magentic loop probe, by folding a square out of a piece of copper wire that's approximately 1x1 inches, and soldering one end to the shield of a BNC and one end to the inner pin.From there you can make things like hardline loop antenna probes, shielded coils (like the one jim williams uses, figure 8 pickup coil in brass tube, or normal coil in brass tube, though these are VERY directional). Honestly I do not find the hardline probes or jim williams probes that useful in comparison to the square magnetic loop or the e-field ball probe. I think they are more useful for work on a PCB, where you can put em right near a trace, then working on equipment boxes, especially in a field setting. If you can put the object your studying on a work bench then thats a bit better.also another interesting one is to take a torroidal inductor (small) and cut it in half with a dremel diamond wheel, then wrap wires around it to make a C shaped coil. I have not experimented with this one yet, as I have lost what i built some where.The thing is, you defiantly want a pre-amp for these things, especially if you are using with a oscilloscope and not a spectrum analyzer.I have not experimented with measuring stuff coming out of computers at higher frequencies between 50MHz-2GHz though. A wideband dual ridge horn (2-10GHz design range approx) picks up some stuff if you place it face down on a keyboard of a laptop, or press it into the front panel of a monitor. High GHz lens horn antennas, I tested 2, 18-21 GHz and 21-24GHz, do not pick up anything from computers etc, but you can get directional signals inside of a room depending on how you aim em. It would be more interesting if I had another wideband preamp for this region though, this was only a direct connection to my HP70000SA. Indoors the pickup at these frequencies is tiny even when the SA is set to most sensitive settings with 20 (well ~15 or so at this frequency dB preamp). I don't like the little preamp modules from ebay using MMIC because their S21? (right?) parameters are kinda all over the place. I would like to get a nice one meant for wideband use with a SA that has a nice linearish slope on it).Perhaps I will retest the high frequencies between 18-24GHz with a open computer running a 3.5?GHz processor. maybe you can get some emissions from the side if its harmonics are not dealt with properly.Unfortunately I did not have any antennas for the frequencies people are interested in, between 100MHz-1GHz. The dual ridged horn for this frequency is large and I ran out of money for metal at the moment. If someone wants to donate me 2000$ to finish my welding table and buy aluminum for a large horn I will happily slave away at its manufacture.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 29, 2018, 02:39:19 pm
content: ....Now I found my "older" SDR who was next to my Antenna who is mount on the roof....So I connect that who use an Filter -> Upconverter -> SDR and have "just" 2Mhz Bandwith.That Antenna is connect to my Indoor CB Antenna.There is an HUGE Spike, Signal at ~26.780Mhz.What could that be?And I use my Laptop when my Pc was powered Down and Disconnect from the Poweroutlet on the Wall and there are the Same Noise! That mean the dont come from my Pc (and what is connected on). I know my Graphiccard/ Display produce noise but the are on the UHF Band.

author: KD4PBS
author_rank: Contributor
timestamp: March 29, 2018, 03:27:50 pm
content: Different SDR, different birdies.Even the USB chip inside the SDR can interfere with the RF section.Perhaps disconnect the antenna and see if it remains?If not, then it sounds as if you have a portable setup. Start walking around your house and the neighborhood to zero in on the signal.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 29, 2018, 03:47:44 pm
content: I was walking around and the noise from here:are everywhere.

author: CopperCone
author_rank: Super Contributor
timestamp: March 29, 2018, 04:16:35 pm
content: I have a plutosdr. I might try the following for you1)use corning optical usb isolator cable2)use lab linear psu at 5v for power3)take before and after spectrograms.I need to make a usb power isolator though so i can power it from a seperate supplyy, as the corning cable still uses power, it simply isolates the datastream. However, i do think tbat there will be extreme noise rejection due to the conversion of usb3 to laser.Digikey has fair quality microusb line filters. I estimated to manufacture it with digikey parts would be like 10$ plus enclosure, but most people cant do an eye diagram test for usb3.0 with some kinda home made construction so i think its worth buying.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 29, 2018, 04:18:14 pm
content: The problem is not my Laptop/ Pc because the noise come over the Air (not from my Pc).

author: CopperCone
author_rank: Super Contributor
timestamp: March 29, 2018, 04:20:28 pm
content: The usb cable can have pickup, even if shielded. And the computers might have similar noise profiles.A good test would be to take your laptop outdoors and make a signal strenght map around where you liveA sizeable distance will help, try 0.5 milesI actually got a backpack that i modified to house a wideband bicone so i could walk around the street while making a spectrograph on a laptop with a plutosdrLots of hills here so it should be interestingI just need to modify my saftey helmet so it has a three foot magnetic loop on top LOL.. Probobly end up hiding from the police from the woods walking arou nd like that

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 29, 2018, 05:05:20 pm
content: Today it Rains so not a good Idea for an Outdoor test.I will try my the CB Antenna on the rooftop.

author: KD4PBS
author_rank: Contributor
timestamp: March 30, 2018, 01:11:12 pm
content: Copper has a good point...Take a drive to the middle of nowhere. Someplace that there are no homes, no buildings, no power lines... nothing.Fire it up and see what it looks like there.Did you ever show us a picture of the spectrogram without an antenna hooked up?

author: CopperCone
author_rank: Super Contributor
timestamp: March 30, 2018, 04:12:32 pm
content: Rofl we forgot to unpplug antenna. Most basic

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 30, 2018, 04:16:41 pm
content: QuoteSadly the Bus is not going so far.Quotenope good idea.I connected the HackRF to my CB Antenna on the Roof and there are the Noise to.So the noise are when my HackRF is connect to my Pc + Laptop.

author: JTY
author_rank: Newbie
timestamp: March 31, 2018, 07:47:56 pm
content: Does the noise level vary based on time of day? I ask, as I've seen street lights with faulty ballasts generating horrible amounts of noise.

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 31, 2018, 11:45:33 pm
content: its during the day to.

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 02, 2018, 03:19:21 pm
content: So when I remove the Antenna from the SDR its dark beside of a peak.Now I tried to remove every powerplug who I could find in the Apartment sure the Fridge, Ofen and some other stuff who I could not remove are still connected.EDIT: The Antenna is outside.