What could the source of the noise be? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 26, 2018, 01:11:57 pm
content: Now I am sitting in the Garden and setup my SDR System with my "Desktop" CB Antenna, Filter and Upconverter.In my Sleeping Room the Noise is insane.Even here in the Garden its very hight. (So I have here just the CB Antenna and it make no sense at all to make screenshot of other Freq.)

author: jmelson
author_rank: Super Contributor
timestamp: July 26, 2018, 09:46:59 pm
content: Well, nearly anything! It could be the laptop, laptop power supply, or nearly any electrically-powered gear in your whole house.Thermostats, dishwashers, fluorescent lights, and on and on. There are so many poorly-designed appliances these days that radiate huge amounts of RFI. And, of course, if it is in a NEIGHBOR's house, that will make it even harder to find and fix.Jon

author: DaJMasta
author_rank: Super Contributor
timestamp: July 26, 2018, 10:06:28 pm
content: Have you run tests in a known-quiet environment? While the variation is significant, it's hard to tell what the noise floor of the radio is or what would be "typical" of a spectrum for the unit, at least for someone like me not familiar with things.I sort of would expect to find more clear peaks from local noise sources... not this broadband stuff - could it be that there's a couple peaks in this range and the resolution bandwidth is big enough that it just catches the peaks in every measurement around them? If you can narrow down the frequency, you can probably narrow down potential sources.

author: rhb
author_rank: Super Contributor
timestamp: July 26, 2018, 11:10:49 pm
content: The first order test is to turn things off and see if that has an effect.If you have a scope make a small (<1/2") loop of copper wire that fits over a scope probe tip with the grabber removed. Use drills of the appropriate size as forms to wind it, not the probe. Then go around and twirl the probe near various things.LED lights are a huge source of conducted emissions, but a $3 eBay EMI filter will fix those. Probe around your PC, especially the PSU fan. I put 1/8" hardware cloth (galvanized or lead coated screen) over my fans and the noise went away.

author: CopperCone
author_rank: Super Contributor
timestamp: July 26, 2018, 11:47:02 pm
content: I noticed with a PlutoSDR if you hit it with a microwave beam of significant power it basically makes the noise floor go completely crazy.. even if its like 3GHz and you are focused on like a 100MHz frequency with a 20MHz span.Also a noise generator I noticed that you might over look is your refrigerator display if its digital and your thermostats (even non-smart) have a pretty bad power supply. GFIC outlets might do it too.Keep in mind things with power bricks typically dont turn off, the power brick will run at no load if the device like a LED lamp is turned off. You need to unplug all the bricks.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: July 27, 2018, 04:22:35 am
content: Quote from: DaJMasta on July 26, 2018, 10:06:28 pmCould also be something using the more modern DC/DC converters with spread-spectrum switching... LT likes to talk about how awesome it is for not having peaks in all their literature.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 27, 2018, 12:38:34 pm
content: Quoteunplugged.QuoteThats simply I call the Authorities the come with Equipment for Measurement. The have the nice expensive R&S Stuff we all want to play with.QuoteNope I would call the Garden a quiet environment. Trust me you dont want know how the noise floor in my bedroom look like.Quotebut that is my biggest concern. The sound like Powerline or some other crap.QuoteThats impossible. My Parents and Grandparents would kill me for!QuoteThat is what?QuoteI try it during the Day.QuoteIts a Laptop and I did "measure" it in the Garden.Quotethe next Embassy is faraway so there should no microwave beam arrund here.Can you ask the NSA, CIA, FBI,... if on of there Sat or Spy Plane put a microwave beam in direction of Vienna?Sadly enough that could happened...The sound like some hight frequency stuff.

author: scdreger
author_rank: Contributor
timestamp: July 27, 2018, 04:41:04 pm
content: I had something that looked very similar that wiped out the entire 40M band with an even S9 signal across its entirety and beyond.I got an HT with a general purpose receiver (TH-F6A) and put it at about 7 Mhz with a small loop antenna I made and walked around the whole house.I traced it to a lithium ion battery charger I had running in the garage, which was incidentally directly underneath the line of my wire antenna outside. Unplugged it and, voila noise disappeared. As some have mentioned, it could be anything ... especially switch mode power supplies/chargers/walwarts/etc.

author: Terry01
author_rank: Frequent Contributor
timestamp: July 27, 2018, 06:37:30 pm
content: Excuse the noob question but what kind of instrument is giving you the pictures in the OP's post? I take it it's some kind of scope or something along those lines?It's well cool!

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 27, 2018, 08:20:30 pm
content: https://www.youtube.com/results?sp=CAI%253D&search_query=HF+SDRJust an ordinary SDR with Up converter and Filter.