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Author Topic: Interference - info on frequencies in general  (Read 451 times)

Weaver

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Interference - info on frequencies in general
« on: May 19, 2018, 01:25:16 PM »

Does anyone know of a website that has a list of likely kit or activities that are sources of RF interference, hopefully with frequencies given? Kitizens have been kind enough to post up some websites with legal radio stations’ frequencies listed but I’m wondering about other kinds of noise sources intentional broadcast other than audio broadcast stations and known unintended offenders too. Anyone seen such a source of info on frequencies ?

Since I am a sad prehistoric person, my world effectively stops at about 710 kHz so I will drool at info below that especially and my particle horizon is ~1.1 MHz.
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GaryW

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Re: Interference - info on frequencies in general
« Reply #1 on: May 19, 2018, 07:58:56 PM »

Some other potential sources are navigation beacons (can't remember the web-site that lists them) and NAVTEX (which is the AM frequency for weather report, etc transmissions to ships!).  I used to get a dip around the NAVTEX frequency but not for a while.
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Weaver

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Re: Interference - info on frequencies in general
« Reply #3 on: May 25, 2018, 05:11:32 AM »

There is something causing a 5.5dB bump over bins at 534.75 - 539.0625 kHz - these are centre frequencies, or 532.5938 - 541.2188 kHz outer edge to edge. I found some mention of “AERONAUTICAL MOBILE aeronautical communication services, NATS” somewhere, but that is all.
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johnson

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Re: Interference - info on frequencies in general
« Reply #4 on: May 25, 2018, 06:55:56 PM »

Are you noticing significant changes in your SNR per tone graphs at certain times of the day Weaver?

In my experience unless you have a nearby-ish AM station that the noise is far more likely to be coming from an offending electrical device either within your premises or in a neighbours (if you have any close ones). I have encountered at least 2 SMPS bricks one for a laptop and another for a monitor that omitted filter coils on their input and caused a sawtooth pattern in the graphs across the whole spectrum and in my case a full disconnect and reconnect at much lower speeds when in use, even from another property. Plasma televisions are another likely culprit, and I believe a neighbour of mine has a seldom used one that causes a noticeable ripple centred on 3mhz but is infuriatingly random in when it appears.
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Weaver

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Re: Interference - info on frequencies in general
« Reply #5 on: May 26, 2018, 02:30:52 AM »

I have not collected enough data yet. I did notice a deep notch (narrow) in bits per bin that disappeared between day and night time. I will take some more measurements.

The feeling I get is that all the sources are things like radio stations or public (eg maritime) communication services, not noise from evil kit. Since I am so incredibly far from civilisation this is what you might expect. Leaving aside my neighbours 100m away - I am the northern most house on the edge of a village high up on the slope that extends about 3/4 of a mile southwards down to the Atlantic - there is no house until you get near to the main road ~4.2 miles to the north of me. Phone line physical route was described in an earlier thread iirc, even pics. The lack of all human activity along the route should make it exceptionally clean. The last 0.9 miles or so, into the centre of Broadford where the NSBFD exchange is full of the usual noise sources associated with housing and activity. The whole run is ~4.58 miles long according to freemaptools.com.

So all is as expected I'm just an antenna and pretty lucky with lack of noise sources. Noise sources that there are are at the exchange end so will be where the downstream signal is strongest, but that isn't good news for the upstream at all, of course.
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johnson

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Re: Interference - info on frequencies in general
« Reply #6 on: May 26, 2018, 02:49:52 AM »

Ah fair enough, if your closest neighbour of unknown technological fortitude is 4 miles away then it doesnt make sense to consider awful power supplies.

The feeling I get is that all the sources are things like radio stations or public (eg maritime) communication services, not noise from evil kit.


Forgive my poor geography, but are the fine folks from the trident base anywhere near you off the west coast there? Can imagine such an installation and their associated maneuvers might be emitting all sorts of strange RF.
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johnson

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Re: Interference - info on frequencies in general
« Reply #7 on: May 26, 2018, 03:00:25 AM »

Ha, 100% on list now. Just happened to be googling GPU/cloud password cracking and VPNs earlier, now sensitive military areas and their emission spectra...
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Weaver

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Re: Interference - info on frequencies in general
« Reply #8 on: May 26, 2018, 03:49:15 AM »

The nuclear submarines are in the Clyde if I remember rightly, in Gearr Loch. (My wife’s boss had a house more or less right opposite them on the other side of the water, he was on the Clynder peninsula looking eastwards.) That’s about 90 miles south of me on the West Coast.

I am on the west side of Skye, IV499BN, but I am so high up that I can see the sea on both sides, the atlantic to the south west and the Linne Shléibhteach - the channel that separates Skye from the mainland. I see Loch Shubhairne and the mainland mountains to the east, quite close. I am wondering now if this is the only place where you can see both seas, not sure. It isn't possible from some places further down the bank when you descend southwards towards the Atlantic because you lose the eastern view because of ground nearby rising up slightly.
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Weaver

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Re: Interference - info on frequencies in general
« Reply #9 on: May 26, 2018, 03:51:08 AM »

I found there is an OFCOM frequency search tool, which seems rather shaky, sometimes hangs or acts weird, but useful when it decides to work
        http://static.ofcom.org.uk/static/spectrum/fat.html

Some stuff is just ranges though, not very specific. And without locations.

But that is the nature / aim of that database.
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johnson

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Re: Interference - info on frequencies in general
« Reply #10 on: May 26, 2018, 04:14:37 AM »

That’s about 90 miles south of me on the West Coast.

Ah well there goes my crackpot theory.

I am on the west side of Skye, IV499BN, but I am so high up that I can see the sea on both sides, the atlantic to the south west and the Linne Shléibhteach - the channel that separates Skye from the mainland. I see Loch Shubhairne and the mainland mountains to the east, quite close. I am wondering now if this is the only place where you can see both seas, not sure. It isn't possible from some places further down the bank when you descend southwards towards the Atlantic because you lose the eastern view because of ground nearby rising up slightly.

Sounds stunning.
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