Trying to understand this noise
It has appeared somewhat recently across this band. I have a galvanic isolator which seems to cut some of it out, however I cant seem to isolate it I have swapped out my power supplies and made no difference. I have my Kiwi in an earthed metal box so I am convinced its coming in off the antenna. I'm using an LNA inline with the antenna however when I remove it and have just the antenna in the Kiwi, the noise exists. Ive also swapped out the coax incase water had got in somewhere.
Given the location of where I am - in an urban enviroment - its unlikely to get any better. Attached is the noise with the noise suppression on, then off.
I think I will need to go back to an active loop antenna, but a decent quality one this time, not the MLA30+ I'm looking at the https://bonito.net/mega-loop-fx/ but damn, its expensive.
Comments
Don't buy the Bonito loop.
Have a look at the Loop Antennas IO group.
https://groups.io/g/loopantennas
You will find some familiar names on there, and one or two, are offering ready built loop amplifier PCB's based on Wellbrook and LZ1AQ's designs.
My personal favourites are versions of the LZ1AQ loop amplifier. But for a bit more money, you could buy a much more versatile ready built LZ1AQ active antenna amplifier, that facilitates both switched active loop and dipole modes. This is highly effective and still costs a fraction of the Bonito (which is based around a cheap video amplifier chip).
https://active-antenna.eu/
Chavdar's other webpages are a goldmine of information and highly recommended too.
https://www.lz1aq.signacor.com/docs/lz1aq-topical-article-index.php
I hope this provides some alternative options.
Martin
Ah this is why I posted here - thanks, Martin! :-)
Some similar electronic smog issues temporarily here. One of the reason is the switching power supply of the internet router itself. How much one can reduce specific noise level in changing power supply towards oldschool linear power supply, anybody can see. However that kind of powering up devices does no more meet power consumption reduction regulations. On the other hand there are probably much more devices in use in the near neighbourhood, you do not have any influence of.
Best solution is a good antenna delivering strong desired signal strength and enough distance to electro smog producing devices.
BTW: In Germany the hams have to pay an annual extra fee for "frequency protection", "Contributions for spectrum assignment". 29,22 Euro coming up 2025. And if the noise gets too much, the authority (BNetzA) can called out for help.
https://www.gesetze-im-internet.de/fsbeitrv/__1.html
I'm almost certain it's coming in off the antenna. My router (firewall) is on a different part of the property, however I do have a decent amount of computer equipment around. That said, my proxmox cluster, NAS and Plex server are in a cabinet, that I have earthed.
The Kiwi is mounted in a metal box with the filters and LNA and that is earthed. This noise is fairly recent.
However, I do have a genuine LZ1AQ on its way - short of that, moving into the country side. :-D
I may even think about re-locating my Kiwi again.
What is your internet connection technology?
I seem to remember DSL having that sort of signature.
I have Fibre and a network like
[Garage]
|
[KSDR]
|
[Switch]------[Mac Mini]
|
+--(60GHz Bridge)-->[Meraki Switch]--[Meraki Firewall]--[Fibre Internet]
|
[WAP]
|
[PC]
Ok, sorry, now I've listened to the WAV it sounds like SMPS.
I had a neighbour with a 1200W computer supply that would put that across the entire HF, he had a noisy supply but would then put that gaming PC in a glass fronted case with extra long white DC lines for appearances.
For ruling out sources in your own home, I used to start a very slow waterfall plot on one RX channel, and another more normal speed. Then go round turning things off/on seeing if that changed anything. Make changes at set times so it is easier to identify trends in the slow plot.
The slow plot can help identify things like "Car A pulls up, one minute later noise starts", "house lights opposite go out, noise disappears", "Garage light off, noise reduces".
Obviously if you have any sort of null on your antenna you can use that to narrow down the direction but that sounds like switch mode. Other things to test are CAT7 cables, and rerouting the GPS antenna, in case there is any pickup on the shields. Little clip on ferrites on the switcher supplies for everything normally helps general noise floor.
Thanks for that.
I’ve swapped out my linear power supplies with some low noise smps (Apple ones) to make sure my diy power wasn’t the issue. Didn’t make any change. Have ferrites around the USB cable and the cat5e cable too.
I might shut down all my equipment in the garage and see if the noise goes away. Annoyingly it’s fairly recent where all the electronics in the garage have been there for a while.
I’m also considering moving the antenna to a less built up part of the section. However that will require running some cable and mounting a pole as the antenna is passive and really needs to be up as high as I can possibly get it.
Do the slow waterfall refresh thing. If you have a PC/MAC run the slow waterfall on that, set it up to show the noise best on the waterfall, leave it running as long as you can, while you walk around or stress equipment, E.G. run a heavy graphical render on a PC, CPU stress test, .
Part of the reason I haven't been on here for ages is that I got fairly obsessed with tracking noise down, got the general level low (fibre lines through the house, CAT7 where it made a noticeable difference) lots of grounding, ferrites and careful cable routing, only to then have any one of my neighbours negate the gains, instantly with a Chinese battery charger or bad PC PSU. I should have changed my username to Sisyphus.
The first step is really to characterise the noise and look for changes during the day. If you can locate it quickly that is great, (walk round with an AM battery radio) but if you at least know it changes on light level, temperature, people being awake in the house, TV on, then that narrows it down. All wires in the house are antennas, those DC lines from power supplies need to be coiled up, and ferrite clipped. I reduced my GPS lead pickup by using a short GPS antenna and a car type repeater from the roof.
If you have a mobile browser running with a waterfall, keep moving around poking and changing things until nothing makes a difference anymore. Even before you locate the particular problem, I bet you'll find one or more background source to reduce.
If you have a cable tracer, the type that uses an audio tone, remind yourself of the noise, then go locking for that pickup, or radiation, on any wiring.