RFI

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Paul
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RFI

Post by Paul » Mon Feb 26, 2018 7:38 am

i do appreciate just how complicated this issue is and just how variable local environmental issues (not forgetting self-created ones), but is there any known issue, whether with the RSP or generally that at least throughout the VLF nad MF bands creates 1 Khz spikes?
Not that I'm without other issues with regard to RFI, although none are unmanageable - just a bit of a niggle.

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g1hbe
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Location: Cheshire, UK

Re: RFI

Post by g1hbe » Mon Feb 26, 2018 9:20 am

Hi again Paul. Closely-spaced spikes are often the product of computer displays, TV's and data transfer devices like PLA's and USB cables. First, eliminate your own stuff by unplugging everything, or if you can run your setup on batteries, turn off the main breaker.
How is you antenna fed? Hi-z wires brought directly into the house are a disaster for this type of noise, you've got to use a coax-fed or balanced feeder system.
A loop antenna such as the Wellbrook can work wonders.

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Andy

NK7Z
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Re: RFI

Post by NK7Z » Mon Feb 26, 2018 1:02 pm

If you are interested in what various RFI sources look like on an RSP-1 I have a catalog of them I am starting at:

https://www.nk7z.net/rfi-snapshots/

It is broken down by category of RFI. An SDRPlay RSP-1 was used for all the black and white images. There are also several other articles referenced, all using the RSP-1 to generate the spectrograms.

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Paul
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Location: SW UK

Re: RFI

Post by Paul » Mon Feb 26, 2018 5:23 pm

Thank for the responses.
Back in the "classroom" - Hand up: The longwire comes indoors directly to a 9:1 balund - there is an abpprox 5M coax feed inside the room - a converted attic, with only the laptop and power sources, which are always in use - no adjacent televisions or other electronic devices. If I can arrange it, I hope to redeploy the longwire to/from apoint permitting an external coax run, when time and other activities permit.
I'm still "building" this setup really and I fear that a Wellbrook is some way off as yet (dive gear and a boat etc compete for slender resources that I have to get past my live-in bookeeper!).
Whether televisions, aquarium heating/lighting, washing machines and other electrical appliances are in use elsewhere in the house or not has no overt effect here.
I have never tried observing the LF/MF spectra on battery power alone (I'm using one of two laptops with identical results).
Apart from the 1 Khz spikes on LF/MF already mentioned I also get noise "humps" at regular intervals (pretty obviously harmonics) between 5 - 9 Mhz.
I have tried this range on battery power without any noticable difference being apparent.
Occasionally, these humps disappear for varying lengths of time - maybe hours - maybe days. This does not appear to be generated within our house and I have long suspected the overhead three-phase powerlines that run almost parralel to the longwire about 30 - 50M away and the same distance from my other antennae (a couple of active mini-whips, a discone and for that matter the indoor hula-hoop).
All display the same humps.
Right at the moment, for the first time for ages, the "humps" are absent and propagation/reception here is perhaps a little better than usual, but not remarkably so.
I am convinced that this is an external source,but just what is not yet clear.
Thanks again for your knowledge and patience...

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Paul
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Location: SW UK

Re: RFI

Post by Paul » Tue Feb 27, 2018 4:36 am

I'll keep this short as I do understand the complexity of these issues.
Just for the record, the "noise humps," previously referred, to are actually present from 5 to 12 Mhz and which were absent yesterday afternoon and evening have reappeared this morning, there is no change to my setup and no domestic activity in the house and very unlikely in the only dwellings anywhere near.

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Paul
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Location: SW UK

Re: RFI

Post by Paul » Tue Feb 27, 2018 6:16 am

https://www.flickr.com/photos/137437642 ... ed-friend/
"Clearish" spectrum and returned "Noise Humps"
https://www.flickr.com/photos/137437642 ... ed-friend/
Is the "Hump" shape suggestive of a source, or is it a silly (not unlikely) silly question?
(Posting links because I continually get "file to large" error when trying to drop images in, or select file - sorry)
Won't be niggling away about this any more, but if you've bothered to get this far -thanks anyway.

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Paul
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Location: SW UK

Re: RFI - The last word - probably

Post by Paul » Mon Mar 05, 2018 7:49 am

[quote="g1hbe"][quote]Hi again Paul. Closely-spaced spikes are often the product of computer displays"
Right on the money Andy..
Just "enjoyed" two days of no electricity thanks to Storm Emma and operating on battery power alone, with no other local electrical interference source, computer generated interference confirmed.
FYI Dell laptop with a SSD & 8GB - runs like a (good) train - haven't yet managed to max out CPU usage - so I'll live with it.
Thanks for your comment and happy that you were right.

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