Question of received wide band pulse noise.

[AdrianH]

Not sure if the correct part of the forum but seen posts on noise in here.

I am picking up what I can only describe as wideband pulse noise across HF bands had it for absolute ages. Noticeable on the old R210 I am working on so I thought I would have a look on an SDR based receiver.

Getting it across many bands with gaps where it is interference free.

I can not imagine it being broadcast in any way and to me must be some sort SMPS some where, I am going through the house turning things off, but just wondering if anyone had similar before? I can only describe it as a time base sound.

I am going to have to get a batch of batteries in for my Roberts R209 and go hunting.

Two pics from the SDR and a zipped mp3 sound clip.

Adrian

[kellymarie]

Ah yes I've heard that noise its especially bad here around 26 megacycles I think its something created by broadband routers or maybe by those cabinets for fibre connection im not sure which be interested to know for sure

[1954Fender]

This is possibly one of the Chinese over the horizon radars, huge signals. You could check using one of the online SDR's at the same frequency. It might save a long walk with your portable ??

[AdrianH]

I got some batteries and I have found it within the house, something I had forgotten and no longer use, but one end was left plugged into a socket and radiated through the house mains wiring. A BT broadband Extender 600. Unplugged it an immediate silence.

Using the Roberts radio the noise was a lot louder every time I got to a group of mains equipment and even the main consumer unit and then I realised behind the router I still had a 600 unit plugged in.

Was surprised at how wide band this thing was, but I guess it must have multiple carriers to get the bandwidth through.

Anyway looking forward to better listening to the HF bands.

Adrian

p.s. Feeling a bit stupid for leaving the unit in a socket in the first place.

[jjl]

Originally Posted by kellymarie

Ah yes I've heard that noise its especially bad here around 26 megacycles I think its something created by broadband routers or maybe by those cabinets for fibre connection im not sure which be interested to know for sure

26MHz is a typical clock frequency for USB controllers, so that would be a possible cause of such interference.

John

(Rhetorical question) I wonder how they passed EMC regulations, answer they didn't and don't, but used the "essential requirements" bit of the CE regulations get out clause.

A link https://www.ban-plt.org.uk/legislation.php , many more available.

[AdrianH]

Looking at that article it looks like the bands of interference I was getting could closely match the charts.

Me thinks these units I have will be mashed to bits.

Adrian

[AdrianH]

The band is certainly a lot better for listening on, I have some hash at present from my temporary SMPS that I am using to run the Larkspur on, but some signals I have noticed before as always present are these three carrier signals probably some form of data transmission I was wondering if anyone knew what they were
4.03MHz, 3.32MHz and 2.70MHz signals: -

Adrian

[Philips210]

Originally Posted by 1954Fender

This is possibly one of the Chinese over the horizon radars, huge signals. You could check using one of the online SDR's at the same frequency. It might save a long walk with your portable ??

Hi.

Yes, it has a certain similarity to the ex Russian woodpecker.

Regards,
Symon

[turretslug]

I can see that these devices are very appealing to those who have no interest or inclination to interest in sub-30MHz radio usage, but the actual concept is frankly outrageous! I used to suffer from it years ago and the fact that it was very markedly absent in the amateur band allocations led me to suspect that it was a smartly malicious thing as opposed to just simple poor suppression of a SMPSU or other appliance and a bit of searching revealed the truth. It soon disappeared though, I assume that it was a near-neigbour's device. Fingers crossed that these devices have nasty little SMPSUs that don't last very long and earn them a poor reputation.

[Julesomega]

Originally Posted by AdrianH

some signals I have noticed before as always present are these three carrier signals probably some form of data transmission I was wondering if anyone knew what they were
4.03MHz, 3.32MHz and 2.70MHz signals

These are regular channels for the LF and HF station at Inskip, Lancashire which also carries the 5450kHz volmet

[AdrianH]

I never found any information as to current frequencies at Inskip, so if you have a link I would be grateful.

I find it strange that there are always 2 out of the 3 frequency slots in use and wonder what the transmissions are?

Adrian

[Julesomega]

What we need is an audio recording so others can hear: someone will know the data type. It sounds like a sort of growl - "Gerrr-ourr-rr" lasting about 1s, then another after 5s, then another after 10s, making a repeating pattern.
You must be within line of sight to the big antenna field with its rotatable LPAs and the big masts for 81kHz, so tune from about 2.5 -5.5 a few times during the day and you'll have them all.

I think the VOLMET must be much lower power, it is quite weak here even at night. They may also carry the 11253 VOLMET, if they do you should be able to hear it

[AdrianH]

I pick up Shannon Volmet the strongest on 5505KHz
https://dxinfocentre.com/volmet-wx.htm

What I think I will do is try to build a RDF loop antenna for RX and see if I can get this in the loft about time I had a play with bits of wire, I only have a long wire up so it is impossible to tell where these signals come from direction wise.

Searching around the Internet and excluding Korean Radio I have found that the frequencies I have listed : -

Can be used for Point-to-point, in civilian use for point-to-multipoint systems and railway applications as well as your typical Military systems.

I do wonder if it is some form or timed polling system, checking for points/signals etc?

Who knows, I am not sure how to record trying to get all three slots as AM, FM or one slot as USB etc. I would guess it is some form of FSK, but just a guess.

The slots do seem to cycle around which is transmitting 011 101 110, just checking here tonight and there is a faint set of slots around 2090KHz and the 4030KHz of not there, or at least very week and below my noise level.

Adrian

[kellymarie]

Is inskip anywhere near blackpool? When I went there a few years ago I noticed what looked like a huge HF antenna it seemed to be in the middle if nowhere and definitely was not a broadcast site. Incidentley the hallucinations were very good happy days!

[AdrianH]

It is indeed near Blackpool, well between Blackpool and Preston.

If you do a google search for HMS inskip you will come back with all sorts one says it is R.N.A.S Inskip or HMS Nightjar
http://www.royalnavyresearcharchive....ses/Inskip.htm

Adrian

[Julesomega]

Looked like this about 20 years ago

[kellymarie]

Thanks I didn't get a good look because I was on a coach and also it was raining now at l know where all those strong data signals between 6 and 7 megacycles they are usually around s7 to 20 over depending on time of day

[AdrianH]

Well the signals have changed a bit at my location Only picking up the ones at around 3320KHz and 2700KHz but the signals have changed as though the units are polling but without answers so each is only one slot as it were.



I also tried another package gqrx to receive the signal and had a loot at the recovered audio using USB and wonder if the signal is 4FSK?



This is as far as I can get I think.

Adrian

[AdrianH]

Back to the original point of the thread, it is some much better now I removed that BT box, on the lower frequencies I still get some noise from the router and internet signals, but nothing like I had makes HF almost useable.

Adrian