Author Topic: Interference and Noise  (Read 46535 times)

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Offline uhf

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Re: Interference and Noise
« Reply #200 on: October 28, 2014, 09:05:58 PM »
I guess I need to find an AM radio. I doubt I have a battery powered one.
Blitzortung.org Station 1175
KIAINDEP3

Offline Einar

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Re: Interference and Noise
« Reply #201 on: October 29, 2014, 06:07:39 PM »
I'm still trying to eliminate 50KHz noise burstst at 100Hz rate. (We have 50Hz mains here.)

I put copper mesh shielding around the 250mm ferrite antennas. That helped a lot. Now I just was up in the attic and wrapped the ferrite antenna leads tightly around the wire going from the antenna shield to the amplifier. That made some difference. The noise amplitude is about halved. I had my surfboard with me so I could look at the signal and it went off the scale while I was touching the antenna leads. Which to me indicate the signal is actually E-field.

So my next attempt will be to skin a coax and put the antenna leads inside the braid so it is completely shielded from the antenna shielding up to the inputs of the amplifier. That should avoid exposing those wires to the E-field as much as I can.

Did anyone try this before? If so, what was the result?

This is station 1209.

I tried turning off everything here except what is needed to run the BO without making any difference. It does seem to be there 24/7. One thing it could be is the overvoltage protection in the main breakers cabinet. But I cannot easily disconnect that. Does anyone have identified problems with those making a "ringing" on the mains?

Offline Cutty Sark Sailor

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Re: Interference and Noise
« Reply #202 on: October 31, 2014, 12:21:21 PM »
Einar, Go back to square one... make the H field leads as short as possible. Remove your shielding and undo any 'loops' in the antenna connections to the amplifier.   Now, I have a very noisy H field environment, and it took me several weeks to find the only 'sweet spot' with minimal interference. You may have to do something similar. I still have issues, and have to run with reduced gain. Since most of my EMI is M type, I cannot run within my system's capability, on H field...
We all have a hard time getting past that "distance" range thinking... see if you can optimize best for <500km (300mi) and you'll work great with the network.
Simplest way is follow EMI with an off station AM radio (530 or 10KHZ) until you find quietest spot... then go from there.  Also, the line freq EMI will change seasonally!  And with daylight/dark hours!  We deal with 60Hz junk here in the US, but issues are similar...  If your EMI is M type, shielding, all the other junk, won't mediate at all....
Mike
« Last Edit: October 31, 2014, 12:25:23 PM by Cutty Sark Sailor »
 

Offline Einar

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Re: Interference and Noise
« Reply #203 on: October 31, 2014, 04:42:14 PM »
M-type? What is that?

Offline Cutty Sark Sailor

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Re: Interference and Noise
« Reply #204 on: October 31, 2014, 05:24:25 PM »
M-type? What is that?

Magnetic... whether Near Field H field magnetic component, or generated 'in space' by a large Electrical discharge, or simply by a moving magnet nearby... Might be a better definition somewhere, but you could say it's "H field" to simplify... however M could also be caused by rotating a magnet nearby, and not be a true 'EM" signal... if you follow me.  So I use "M" because I'm not exactly sure of source, perhaps, but do know that it's "Magnetic"  not "Electric"... there are some 'sources' that consider "H Field" as a more complex plane of force than "E" Field, and refer to "M" as an "H field component" or similar...  However it's implied or defined, an "M" with motion, or changing strength, cannot be shielded on an H field Horizontally polarized antenna... It's gonna induce 'current' and therefore voltage, in a receiver's front end.  Since the "M" (H) is typically "Horizontal"... an E field "Probe" (vertical) is more or less immune to "M" (H) field.  An "H" field (horizontal) antenna can, however, be shielded from some "Electrical" (E field) signals, which might have a very weak (because of distance) "M" component.... the idea is to mediate "opposite" planar current/voltage induction into the receiving element... and only detect the 'plane' we're aiming for -- "E" (Electric) "H" (magnetic)... with "M" being a possible "Magnetic" source from (wherever) that we don't desire.... arrrrrrrggggggghhhhhhh.......
Confused?   Yeah, me too...  #-o  and I probably have some of this wrong... oh, well.....   :twisted:
I Think....  :twisted:
Mike
 

Offline Einar

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Re: Interference and Noise
« Reply #205 on: October 31, 2014, 06:27:00 PM »
You should buy this book: http://www.bicon.nl/emc-book.html

It's really good reading!

And I found the source of my noise! It is my Samsung laser printer. Guess I have to try quieting down the rectifier. That should be possible to get rid of. For now switching it off will have to do. The noise is completely gone. All I see now it that it's getting cold, and thermostats click on/off in east, south, west and north.

Offline Cutty Sark Sailor

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Re: Interference and Noise
« Reply #206 on: October 31, 2014, 06:42:32 PM »
You should buy this book: http://www.bicon.nl/emc-book.html

It's really good reading!

And I found the source of my noise! It is my Samsung laser printer. Guess I have to try quieting down the rectifier. That should be possible to get rid of. For now switching it off will have to do. The noise is completely gone. All I see now it that it's getting cold, and thermostats click on/off in east, south, west and north.

Yeah, I sympathize with the Laser Printer.. I gave a brand new ACER, top of the line, PC to my son because it radiated so much it messed up BO.... I've got 8 HP pcs, and 2 laptops that don't interfere, unless the oldest laptop is within about 15' of the H Field....
Outstanding that you found it!   Feels good, doesn't it! =D&gt;
That's part of the fun... this 'interference' with what we used to call 'interference' when DXing or listening to radio~

Thanks for the tip on the book,.... but the issue with me is I've (at my age) forgotten more than they teach today about such things.... and my 'grey' cells have turned to 'grey hair' ... you should hear 'em scream when one falls out...   too much learning curve anymore... and not enough life expectancy to learn and absorb much more... Hell, I remember when "Siemens" were 'Mhos", unless I've forgot it...   Probably get that wrong also...
 

Offline Cutty Sark Sailor

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Re: Interference and Noise
« Reply #207 on: October 31, 2014, 07:23:31 PM »
Einar... if you've got a screen shot or two of that printer EMI when active, why not post 'em here????   Might help folks...
Mike
 

Offline Einar

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Re: Interference and Noise
« Reply #208 on: November 01, 2014, 01:32:47 AM »
Of course, here they are. 2 screenshots with a few minutes between them. No change in amplifier settings.

Also a screenshot from a scope showing a longer sampling in the time and frequency domain. Notice that the bursts are reocurring at 10ms intervals, and our line frequency is 50Hz. The noise itself is 49-50KHz. This variation is probably temperature dependent, as it is stable for long time intervals. The scope was connected to the output of chA on the H-field amplifier. I don't remember the amplification setting at that moment, but I think 400 or so.

And yes, it should be helpful as it is typical for anything that have a rectifier bridge feeding a capacitor. Which in practice means almost every appliance available today. You just have to find the offender and hope it is within your reach to turn off.

It should be possible to quench this noise by either modifying the line filter or maybe just drilling a hole in the plastic case to access the chassis and ground it properly. Something that should not be done without checking the safety aspects of it though. If touching the ground and the printer chassis at the same time before they get connected might lower your heart rate to zero.

Regarding the grey hair, you just may underestimate my number of grey hairs. Although they actually are getting fewer in number. Learning is harder when getting older, but as fun as before.
« Last Edit: November 01, 2014, 02:07:26 AM by Einar »

Offline Einar

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Re: Interference and Noise
« Reply #209 on: November 05, 2014, 03:54:04 AM »
Are there any explanations her on the different station statistics on Blitzortung.org?

I believe my station (1209) is pretty Level now, but several of the Statistical graphs I don't really understand.

We're into the Cold season With lots of heater thermostats switching, so I think the noise that is there now is something I cannot do much about. And I *believe* the statistics support that. But I would rather like to be able to exploit the data better than I can do without really understanding what they mean.


Offline WA7FWF

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Re: Interference and Noise
« Reply #210 on: November 10, 2014, 10:39:23 PM »
Well things seem to be working good here, picking up strikes off the east coast as I type, but there is a noise I can't seem to track down, mostly at night but I have seen it during the day, what is odd  is the waveform spans magnetic and E and looks pretty weird. I'm posting a pic in hopes someone says hey! I have seen that one before, fortunately at this point its pretty intermittent.

Thanks
Kevin

Offline Cutty Sark Sailor

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Re: Interference and Noise
« Reply #211 on: November 11, 2014, 02:36:23 PM »
First of all.. the image shows very high gains... which aren't really necessary... resulting in what appear to be distorted waveforms in E channels... Those signals are likely to be rejected.   Second there's no real advantage for 'network' operation to detect signals 5000KM away..., there are other stations who provide a more 'accurate' TOA TOGA, and signal representation...
My suspicion is you're operating in "automatic"  with a few filters switched in.   My suggestion would be to "restart" optimization by following our experience at http://www.wxforum.net/index.php?topic=22710.0 which deals specifically with running a Dual Field system... based on the 2014 Red System...
You're looking good.... system looks quiet, and with 'illustrated' signals coming at such Hi Gains, you will probably have an excellent station...  :-(.. unlike mine... I've similar interference and it's much much closer, apparently, than yours... so I can't run at your capability...  In both cases the signals have a strong Line frequency emission, with spikes,... so your signal may in fact be a tad weaker than mine, you appear to have strong "Near Field" magnetic, plus very strong electric arcing...  hard to tell without FFT signals, and some other data...
Welcome aboard!
Mike
 

Offline WA7FWF

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Re: Interference and Noise
« Reply #212 on: November 11, 2014, 03:31:59 PM »
  Mike your correct on many points, it is running automatic with filters, when I can be around for awhile and something good is brewing I will put it back into manual,  and I have gone with the setup link for H and E  and I get everything set and its great and then I come back later and its almost in interference mode or I am seeing nothing.  I'm also definitely in newbie mode learning, so if I'm not going to be around  I leave it in automatic even though I know that is not optimum but I figure its "safer".
  I wondered if the odd waveform was from clipping in the amps and I guess so, I could turn everything down and leave it real low but then I miss a lot of things that other stations nearby see, I was trying to find a sweet spot where I see a good bit  while not putting 20,000 signals to the servers, just trying to get a better feel and understanding which settings are better, right now even with it in automatic it tends to stay around 500 for signals  but then noise in the neighborhood kicks up and I will see it in the 3000's for signal. I have never seen anything for what an excessive amount of bad signals might be.

Thanks
Kevin

Offline CF20852

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Re: Interference and Noise
« Reply #213 on: February 15, 2015, 11:56:46 AM »
The U.S. Federal Communications Commission has an on-line table of frequency allocations at http://transition.fcc.gov/oet/spectrum/table/fcctable.pdf that some folks might find useful for identifying possible sources of interference.  The International Telecommunication Union's (ITU's) international allocation table from Article 5 of the ITU Radio Regulations is on the left, and the U.S. Federal (controlled by NTIA) and Non-Federal (controlled by the FCC) allocations from the FCC Rules, 47 C.F.R. Section 2.106, are on the right.  Attached below is a snapshot of the U.S. side of the table, for the frequencies from 9 kHz to 90 kHz.  The footnotes are important, for example, US2:

"In the band 9-490 kHz, electric utilities operate Power Line Carrier (PLC) systems on power transmission lines for communications important to the reliability and security of electric service to the public. These PLC systems operate under the provisions of 47 CFR part 15, or Chapter 8 of the NTIA Manual, on an unprotected and non-interference basis with respect to authorized radio users. Notification of intent to place new or revised radio frequency assignments or PLC frequency uses in the band 9-490 kHz is to be made in accordance with the Rules and Regulations of the FCC and NTIA, and users are urged to minimize potential interference to the extent practicable. This footnote does not provide any allocation status to PLC radio frequency uses."  Unfortunately, we Blitzortung operators are not "authorized radio users".
« Last Edit: February 15, 2015, 12:11:27 PM by CF20852 »

Offline geewizard

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Re: Interference and Noise
« Reply #214 on: March 27, 2015, 05:20:10 PM »
I'm new to this sferics thing and finding the MANY sources of interference.  I'm not new to electronics, radio, etc.

That said, I've got these big noise spikes at 60kHz and about 125kHz.  The one at 125 kHz is persistent.  Are they harmonics or something of a 30.5 kHz signal?

Any ideas?
Station 1187

Offline Cutty Sark Sailor

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Re: Interference and Noise
« Reply #215 on: March 27, 2015, 07:02:35 PM »
Watching your sigs for awhile on the Hi res at http://sferics.us ,
and I think you've got at least 3 separate disturbers... about 30kHz, 60kHz and 80kHz.
I think the 120 ± might be a 'mixing' artifact.  The 60kHz± is strong, and probably localize.
You're also running 8*16 gains, so you might see what things look like at 10*10 or even 8*8.
either way, the server seems to have no problem with the disturbers, though it gives you a
higher signal count... so what, no big deal.

To me, they have all the appearance of localized electronic devices, timers, computers, something nearby.
Security system, similar... .
However, in the end, you may likely find this all related to the Jim Creek Naval transmitter, about 280 miles
west of you. At a million+ watts and a humongous ground system... And who knows what goes on in and around Fairchild, also west of you...
But I think it's local... in your home or nearby.
 

Offline Cutty Sark Sailor

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Re: Interference and Noise
« Reply #216 on: March 28, 2015, 11:03:00 AM »
Lighting ballast drivers like to run at 62kHz
Some Monitors, especially LG, like 61kHz
Some Pest repellent like 32-62kHz
Some Printers like to run at 62kHz
Lots of AC-DC converters, ditto.
Your neighbor has a big mobile Camper/ trailer on constant charge????
 

Offline geewizard

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Re: Interference and Noise
« Reply #217 on: March 28, 2015, 11:10:15 AM »
Thanks Mike.

Are those spikes affecting my contributions or can I ignore them?

Could the 60 kHz be WWVB?
« Last Edit: March 28, 2015, 11:38:39 AM by geewizard »
Station 1187

Offline Cutty Sark Sailor

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Re: Interference and Noise
« Reply #218 on: March 28, 2015, 04:43:01 PM »
All the way from Ft. Collins?  Don't think so, but anything could be possible... Who knows what could flow up the mountains and through that big Yellowstone Magma chamber between you. 
I think it's local... a fluorescent or something.  I had a high end ACER computer last year... could not run it in the house, it radiated so strongly.  Matter of fact, I gave it to my son, who lives in Fort Collins.  :-k ....I'd rather think it's that damned ACER interfereing with you than WWVB. I could tell him to unplug it, and see if your EMI goes away  :twisted: Getting it 1250 miles away from me eliminated my issues with it.

Start pulling breakers, see if you can make it go away, or at least discover which leg of your residential ac service might be driving it.
As for the usage of signals.... as long as you keep your controller out of interference mode, you'll send signals. The server will ignore that, it'll just give you a higher signals count... It doesn't look like lightning, and the server know it isn't.  Yeah, you might miss an actual stroke once in awhile, but we all do. Lots of stations, especially in Europe with all the NATO mil traffic, especially sub comm, the strange regulators etc they have for solar power, etc... they get along fine.
Just wait for spring, and watch the forums when folks start firing up those robotic lawnmowers!  They drive operators nuts! And they're on power 24/7 since they stay plugged in to charging station!
 

Offline geewizard

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Re: Interference and Noise
« Reply #219 on: March 29, 2015, 11:01:14 AM »
From what I read on the NIST site regarding WWVB signal strengths, it will be about 100 microvolts per meter or greater in Spokane.  I figure if a radio controlled clock can get the signal, so can our equipment?  But, like I say, I'm a newby at sferics.

I know that my own fluorescent lights kill my station.  But, the e-field antenna is out in the garage 5 feet away from the lights too.  So, perhaps the neighbor's lights....

I did an experiment yesterday where I put the E-field antenna and preamp out on my weather station mast and ran about 100' of quad shield RG6 back to the amp.  The data signal from the weather station (a 1-wire microlan) just killed the e-field signal.  Powering down the 1-wire system made it much better but....I want the weather station too!

So, I put the e-field antenna on the garden shed roof as far away as possible from the weather station mast.  And got more noise but not from the weather station data cable.  Still evidently an unusable site though......

More experimenting today......

I haven't seen any robotic lawnmowers in my neighborhood.  Glad of that.  Some electric fences nearby.  I've eliminated the one BIG source of RFI and that was my electronic dimmer switch and LED flood light.  Those things just howled.

I'm not ready to ask Jim Creek to turn down the power quite yet..... :grin:
Station 1187

Offline CF20852

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Re: Interference and Noise: wireless power transmission
« Reply #220 on: April 10, 2015, 08:23:47 AM »
In case you need something new to worry about, read this document on wireless power transmission, which includes mention of VLF frequencies:
http://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-SM.2303-2014-PDF-E.pdf

And this article that talks about wireless power transmission to electric buses at 20 kHz in Korea:
http://www.bbc.com/news/technology-23603751

Offline Cutty Sark Sailor

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A Wow Moment! The "Pesky Project"
« Reply #221 on: April 14, 2015, 09:23:59 PM »
  Looks Good So Far
How to take a pesky from this:


To This (Compare the images closely):


... and still have signals like this:


Now to prototype another, and apply to A channel... #-o
and see how it goes for awhile...
http://sferics.us/bo1/index.php?topic=136.0
Follow it there, until it's ready for prime time...
After all, that's one of the purposes of the Region 3 Operator's Site!
 :twisted:
 

Offline robo

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Re: A Wow Moment! The "Pesky Project"
« Reply #222 on: April 16, 2015, 09:26:37 PM »
and see how it goes for awhile...
http://sferics.us/bo1/index.php?topic=136.0
Follow it there, until it's ready for prime time...
After all, that's one of the purposes of the Region 3 Operator's Site!

Mike, why do you post links to a secret forum here?

Bye,
Robo :)

Offline Cutty Sark Sailor

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Re: Interference and Noise
« Reply #223 on: April 17, 2015, 11:38:00 AM »
When the innovation is proved out ,operationally, I'll bring it here, and to the BT forum also. Meantime, Region 3 operators can provide their input, or go ahead and try it, at the link posted.  There's no sense in bringing junk into a public forum, messing folks up, confusing them even, until something might possibly be viable and applicable.  The link is for Region 3 operator's convenience. That's why.

Now, proving it out with theory, is beyond me,... at this stage of life. I've forgotten too much... .But I'll say this, this thing appears to be kicking butt this morning with "Mark I" applied to both channels. Hopefully after some observational and operational time I'll present it as a done deal, works great for me in my situation, folks can have at it, and those who choose to figure out the whys and wherefores can do so. So far it's doing something I didn't quite expect, results-wise... figured it was just another waste of time...
 

Offline Cutty Sark Sailor

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Re: Interference and Noise The Pesky Mark I
« Reply #224 on: April 20, 2015, 07:29:05 AM »
Ok... Here it is:

Yeah, I know, I know... probably a hundred reasons it shouldn't work better than a round over core shield. Don't care.

What I do care about, that for those couple of 'pesky' intermittent E components that a round close shield, of foil, copper, pipe, ribbon cable... whatever variation had no effect... this does. somebody else can figure it out.... and a bumble bee can't fly.

The idea appears similar to "trough' shields for ferrites.
Did find one specific reference to this idea, where the author appears to be using the same paradigm... attached 1990 article.

The History? 
I found an 50 year old 'shorthand' note I'd scribbled when ELINT / ECM tech in SEA, possibly relating to a communications jammer  or possibly a DF system.... from a discussion with a Hallicrafter's tech rep, I suspect.. 
...took a few minutes to decipher a couple of things, the rest is obscure, but ....
I wish I could reconstruct the conversation that elicited the 'cryptic' note, and the context of that conversation... I know that it likely had to do with a communications freq jammer, or probably our LF DF antenna. In the context of the war environment, we were constantly looking for calibration references, etc, and Hallicrafters was instrumental in both those systems, at the time,... so looking at the references I suspect we were brainstorming checkout and diagnosis for "off the cuff", quick reaction shop evaluation and or flightline troubleshooting, if you follow me.... The receiver/ transponder shop was enclosed in a Faraday Cage to keep out noise, but we needed to simulate airborne, as well as flightline, situations at times... that one rotary DF antenna was notorious for generating LF and VLF electrical noise into adjacent systems when the commutators began to fail... so we were probably looking at a "quick diagnosis" for noisy rotor.  One thing that is curious is the note explicitly states that " sides= c x 10 "  with some other faded and scribbled crap... and I do recall, somehow, that the c was referring to the core diameter of a ferrite rod.... I also interpret the scribblings to hint that this applied at certain frequencies, but there's no reference to which ones.... from the general context, I assumed we were discussing the bands between about 240 Hz (typical commutator noise pulses) up to about 2mHz. 

The other thing I'm wondering is if one of the scribblings might say that the "thickness of the shield material"  is important... can't prove that, but I suspect it strongly.  The Pesky Mark I  is just covered with copper foil.  Both antennas are now in "Mark I" shelds... and looking fine.  Prototype headed for the museum shelf.

So...  there you go... I'm minus 2 or three intermittent low level E component peskies on my H field. that have pestered me for a year or so.The theories, math etc are beyond this old tired brain. Have at 'em.

Mike


« Last Edit: April 20, 2015, 07:37:44 AM by Cutty Sark Sailor »
 

 

anything