what can it be this huge interference.... ??

General discussions
dxdx65
Posts: 5
Joined: Tue Apr 11, 2017 5:23 am

what can it be this huge interference.... ??

Postby dxdx65 » Tue Apr 11, 2017 4:28 pm

Hello Gents,
I need your suggestions: I just installed my new ALA1530LNP and connected to SDRPLAY2. Even with this antenna I experience a huge noise among 0 and 300 Khz (the gradually dropping). If I disconnect the antenna ( any antenna, not only the ALA) the noise goes away, thst should mean it's coming from the surrounding. I live in a flat at the last floor and the antenna is placed on the flat roof above me. I shouldn't have any specific jammer apart the usual for a building ( elevator, water pumps,..). Plese see the attached image: can you recognize any possible source that I can investigate....do they look like armonics coming from an electric appliance....??? Unfortunately on VLF and LF it's just noise, almost no signal can come out and I risk to trow away my money with this nice antenna too.

Thanks a lot
Franz
Attachments
Cattura2.jpg
Cattura2.jpg (103.77 KiB) Viewed 1819 times
Last edited by dxdx65 on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
Reason: No reason

mikexeno
Posts: 60
Joined: Wed Jul 08, 2015 3:18 am

Re: what can it be this huge interference.... ??

Postby mikexeno » Wed Apr 12, 2017 3:37 am

What is your location?
What is in your surrounding area? Solar panels? LED lights for the streets?

That looks like power line noise to me. How high up the band is the noise?
Did you put a rotor on the loop? How is it pointed?

Reason: No reason

dxdx65
Posts: 5
Joined: Tue Apr 11, 2017 5:23 am

Re: what can it be this huge interference.... ??

Postby dxdx65 » Wed Apr 12, 2017 5:21 am

Hi Mikexeno,
I'm located at the border of a small city, surraounded by houses and 1 km from my qth there are a couple of small manuf. plants.
In my street there are recently installed LED lights , but they are off during the day (off or on does not change the situation here). At 200 mts I have also a small gas compressor on the street, and I'm looking at that , as sometimes the noise disappears after 11pm until early morning and I can hear an electric motor running..
Regarding the antenna beam, I tried to rotate it but it seems the noise level is not affected that much from the direction ( might be some dB but I cannot even see it on the screen ..). I tried also to ground the signal (temporary to a metallic water pipe, I have no other option), but no effects.

Is there any "tool" or tip I can use to define the direction of such LF noise..? ..I'm really frustrated to have a good receiver and antenna but with such limit.... :|

Thanks again for your support,
Franz
Last edited by dxdx65 on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
Reason: No reason

dxdx65
Posts: 5
Joined: Tue Apr 11, 2017 5:23 am

Re: what can it be this huge interference.... ??

Postby dxdx65 » Wed Apr 12, 2017 5:29 am

@ Mikexeno:
I forgot ..here you can see better the amplitude of the noise that then gradually reduces over 300 KHz..
Thanks
Attachments
image1.PNG
image1.PNG (131.13 KiB) Viewed 1761 times
Last edited by dxdx65 on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
Reason: No reason

g1hbe
Posts: 239
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire

Re: what can it be this huge interference.... ??

Postby g1hbe » Wed Apr 12, 2017 8:18 am

It could be almost anything, from any kind of device that uses a switch-mode supply to a plasma TV. I see the spikes occur every 10 KHz, which seems a bit low for most switch mode supplies. If you have a radio which covers longwave you could go out and hunt it down, but be warned that low frequency noise is often radiated by the local mains cabling making it seem to come from many directions.
You say the noise goes away when you unplug the antenna - do you mean unplugging the Wellbrook from its interface box or unplugging the interface box from the RSP? This may tell us something. I had a very similar problem at LF and it was coming in on the mains supply. Unplugging the Wellbrook reduced it, but it was still there. Unplugging the interface from the RSP killed it completely. From this I concluded that I had a ground loop problem.
To cut a long story short, I found that bonding all my radio equipment together with croc-leads stopped it.
One last question - are you using the Hi-z input or the SMA input?

Reason: No reason
Andy

DanubeBCL
Posts: 180
Joined: Sat Jul 02, 2016 12:39 pm

Re: what can it be this huge interference.... ??

Postby DanubeBCL » Wed Apr 12, 2017 8:45 am

Agreed: This can be almost everything. Photovoltaic inverters, lawn mowing robots, LED bulbs... The engineers have a vivid imagination in creating all sorts of RF noise with their devices. This depends on the model, manufacturer of the device and one can seldom identity a noise source from a spectrum image alone. There are too many noise sorces out there.
For switched PS 10 kHz are a bit too low, that's true.
BTW: The expression "Power line" interference is in Europe often used for noise from "powerline modems (PLC/PLT)". But these inventions of the devil do not make noise below 1.6 MHz. There are also some "smart home grids" on VLF/LW in several countries working similar to PLC, but I am not aware that they use 10 kHz spaced carriers. But you never know...
The only way to find out what it is really is to spot the source with the ferrite antenna of a small LW radio or a magnetic loop attached to a "mobile" RSP on a tablet PC or similar. And pray that the "owner" of the noise source is cooperative. The spectrum supervising authorities in many countries do not care about RF noise.

73, Heinrich

Reason: No reason

PG3
Posts: 29
Joined: Mon Nov 14, 2016 6:04 am

Re: what can it be this huge interference.... ??

Postby PG3 » Wed Apr 12, 2017 1:42 pm

I have an ALA1530LNP and RSP1. I have found it necessary to ALWAYS have a MW (AM broadcast band) filter connected between the antenna and the input to the RSP (unless I'm wanting to chase MW DX in which case I replace the filter with a 20dB pad). The ALA1530LNP is very efficient at the MW frequencies and if you live where there are many high power MW stations close by you'll be plagued by massive images and IMD no matter where you tune without the filter. Without the filter I have similar spectrum interference down in the 0-500KHz VLF range.

Reason: No reason

DanubeBCL
Posts: 180
Joined: Sat Jul 02, 2016 12:39 pm

Re: what can it be this huge interference.... ??

Postby DanubeBCL » Wed Apr 12, 2017 3:00 pm

IMD normally should be seen all over the spectrum, not only limited to a part of it with sharp cutoffs.
But indeed the 10 kHz spacing could indicate IMD from strong local US mediumwave stations. In this case the interfering carriers should be modulated with broadcast content and change their amplitudes (fading).
It's true: Before I run around in the village with direction finders I would try a simple attenuator (or MW filter if at hand).

73, Heinrich

Reason: No reason


Return to “General”

Who is online

Users browsing this forum: No registered users and 6 guests