Topic: Interference and Noise

[Cutty Sark Sailor]

I have an ungrounded and unshielded ferrite antenna 6.8 system.

Is the attached image a reasonable signal profile?

Something doesn't look right. I'm not familiar w/greens, but:
Is 256 the default sampling rate for Green systems, not 512???, and  0 sample before trigger?  Zero Gain???

The Green (6.8USB) uses a "dumb" amplifier. The gains are set by jumpers (a pain, believe me) and not PGA (Programmable Gain Amplifier). The windows-based tracker program has no idea about the gain setting. The threshold on a stock "green" is fixed at +/-417mV, although my modded unit is adjustable. The tracker doesn't know what this is set to either, the "green" controller uses a simple analog comparator that triggers based on a reference voltage.

Also the scope-like trigger window is different hence the different trigger points. I believe that the buffer can store the pre-trigger data in "red".

Here is a web page where I have both of my stations "red" and "green". I also have the FFT plots for both systems.

http://www.miraculon.net/signals.html

Greg

So Greg, your're saying that SCHWAB's signal looks fine... right???

[miraculon]

It would seem so. At least as far as "gain" and sample rate info is concerned. I looked over at Blitzortung.org for a mention about the differences between red and green in the gain and sampling windows, but I can't seem to find it.

Greg

[schwab]

What I am trying to find out is if my Green 6.8 system will be optimized and benefit from Miraculon's input terminator mod or not.

I am happy to post additional images although lightning activity is low at the moment.

Thanks for your expertise, time and consideration for this electrical novice.

[miraculon]

What I am trying to find out is if my Green 6.8 system will be optimized and benefit from Miraculon's input terminator mod or not.

I am happy to post additional images although lightning activity is low at the moment.

Thanks for your expertise, time and consideration for this electrical novice.

I have actually modified the mod, so to speak. I changed to a 10K resistor for the terminator. If you make it as I did with a jumper, you can plug it in and out easily. If you need the part number on Mouser for the 2-pin socket with solder tabs, let me know and I will post it here. If you get several of the sockets, you can make up a variety of terminator values. e.g. 2.2K, 5K, 10K, etc. to experiment with.

I also set the filters to the 34KHz settings. The 17KHz filter settings were a way to deal with the resonant peak of the ferrite antennas. By adding the terminator resistors, the resonance is reduced so the bandwidth can be opened up. Red has wider bandwidth than Green. I was trying to mimic the Red system configuration as much as possible.

The effective output of the antenna will change, so you will need to re-adjust your gains accordingly.

Remember to set the input to "single ended" with jumper IA-3 and IB-3 in addition to adding the terminators. Otherwise, the jumper resistance will not be across the input. Changing to single-ended was the best noise countermeasure that I did. "Red" went to single ended. There was simply too much common-mode noise voltage for the differential input to cope with.

Greg

[i_fiorentino]

Hi guys,
i've solved most of my noise issues.....it was my power line!
But it remains a light fluctation like the image below:

https://www.dropbox.com/s/p4m6y4vsa5hbtur/Cattura2.PNG

OR

https://www.dropbox.com/s/el5eh2klkia949b/Cattura3.PNG


I've tried to turn off my emergency light, pc, tv lcd, decoder sat, my boltek antenna, lap top, sat signal extender, all my kitchen appliances ecc.ecc. without lucky.
I'm beginning to lose hope
My actual settings: https://www.dropbox.com/s/2ti5phwpmtxf2bz/Cattura5.PNG
Thanks in advance for any help or advice!
Regards,


Alessandro

[miraculon]

Alessandro,

In my opinion with 20cm ferrite antennas, your gain is too high and your thresholds are too low.

I would try reducing gain. Your product of 10x16x40 = 6400, is very high.

Channel A Gain [10] [16]
Channel A Gain [10] [16]

(x 40 is not a user setting)

I would reduce it to some combination that gives a gain in the range of 1000-2000. You could try 5x5x40=1000 as a starting point. Also, if you find a good combination, make the first number the larger one. For example, if you use a gain of "1280" use something like 8x4x40, not 4x8x40. (the "40" is the fixed gain that you cannot control).

Also, the threshold of 76mV is too aggressive. Try the default 120mV or even 200mV.

Once you stabilize to "Normal" instead of interference mode, you can then try lower thresholds and higher gains. You need to make gradual changes. Don't be surprised if you get a good "Normal" mode for hours or even days, and interference mode comes back if some kind of new noise appears.

Greg

[i_fiorentino]

Alessandro,

In my opinion with 20cm ferrite antennas, your gain is too high and your thresholds are too low.

I would try reducing gain. Your product of 10x16x40 = 6400, is very high.

Channel A Gain [10] [16]
Channel A Gain [10] [16]

(x 40 is not a user setting)

I would reduce it to some combination that gives a gain in the range of 1000-2000. You could try 5x5x40=1000 as a starting point. Also, if you find a good combination, make the first number the larger one. For example, if you use a gain of "1280" use something like 8x4x40, not 4x8x40. (the "40" is the fixed gain that you cannot control).

Also, the threshold of 76mV is too aggressive. Try the default 120mV or even 200mV.

Once you stabilize to "Normal" instead of interference mode, you can then try lower thresholds and higher gains. You need to make gradual changes. Don't be surprised if you get a good "Normal" mode for hours or even days, and interference mode comes back if some kind of new noise appears.

Greg

Greg,
thanks a lot for your kind support!
What about signal? (image on the post above)

In your opinion is it normal that ondulation?
Or it could compromised the detection of lightning by the antennas?
Thanks again.
Regards,


Alessandro

[miraculon]

I am not sure what that is, or what the source might be. It appears to be about 1000usec between peaks. This works out to 1milli-sec and corresponds with a 1Kilo-Hz signal.

Did you try disabling the PWM backlight dimming on the display? I don't remember what frequency that runs at, but I saw noise due to the display. I set my PWM to 100%, then 0% after 60 seconds.

Also with the huge gain you had, it is very susceptible to a variety of noises. Is it still there with lower gain settings?

Greg

[scarecrow93]

Add Synology NAS to the list.

I've been getting this signal for awhile now but haven't been able to isolate it until today.

The NAS is located 10-15 feet from the antennas (through walls...etc).  Turn the NAS off and it's gone.



Lance
Huntingtown, MD

[miraculon]

Here is one that I encountered today. I was running high gain (1600) all day, then this suddenly started. I took the Cornet Micro sniffer out and there was a magnetic field to the south side of the house. Don't know what it was though.

Greg

[i_fiorentino]

Hi guys,
i've attached some images about a possible noises.
Please, could you give me an eye?
What about this noises in your experience?
Should be shielded the cable that goes from the controller to the antennas?









Thanks in advance.
Regards,


Alessandro

[miraculon]

Should be shielded the cable that goes from the controller to the antennas?

Yes, use STP CAT5, Shielded for the antenna/controller connection. I gave this advice previously:
http://www.wxforum.net/index.php?topic=20424.msg196452#msg196452

Greg

[fotogw]

Hey all,

Great thread!

Got 2 screenshots of confirmed interference.
- picture 1 is an electric fence at approximately 100 meters distance to the antennas. Occurs ~1x per sec., can be heard clearly by a small AM-radio.
- Picture 2 is the controller LCD @60% brightness. This slow rising and falling of the signal stops when the brightness is set at either 0% or 100%.

Gerhard

[Cutty Sark Sailor]

Good addition, Gerhard!   Thanks... maybe we'll actually fill Greg H's 'rogues gallery' with evil emis.... !  I was especially interested in the NATO Submarine signals at 23.5kHz in the BT thread...   

[scarecrow93]

Here's something new!  About 3 days ago, I started getting this signal.

It runs at 120Hz (measured on a non-lightning day).  It's pretty steady in amplitude and cycle.  It runs all day without any breaks.  I know it's not the antennas or system.  I can rotate the antennas and the signal moves to the other side.  I've turned off and unplugged almost everything I can get to in my house trying to isolate it with no luck.  I've relocated the antennas a couple of times and it follows.

So far,  I've compensated by moving the entire interference over to channel B and raising the trigger level to just above the interference peak.  I've seen whenever a strike happens, it'll still raise the amplitude of the signal just enough to trigger.

Any guesses what this is?

Thanks!

Lance
Huntingtown, MD  #724

[Cutty Sark Sailor]

Here's something new!  About 3 days ago, I started getting this signal.

It runs at 120Hz (measured on a non-lightning day).  It's pretty steady in amplitude and cycle.  It runs all day without any breaks.  I know it's not the antennas or system.  I can rotate the antennas and the signal moves to the other side.  I've turned off and unplugged almost everything I can get to in my house trying to isolate it with no luck.  I've relocated the antennas a couple of times and it follows.

So far,  I've compensated by moving the entire interference over to channel B and raising the trigger level to just above the interference peak.  I've seen whenever a strike happens, it'll still raise the amplitude of the signal just enough to trigger.

Any guesses what this is?

Thanks!

Lance
Huntingtown, MD  #724

Hey, Lance... probably not in your house.

1. Which direction is B picking signal up/ E-W or N-S  ?
2. Is it daylight only, or 24/7 ?

If your 'member map' pin is close to actual site:
You've got some rather big power lines,  a school, just north, and businesses to the NNW, etc on the map. What're the businesses?

[i_fiorentino]

Hi guys,
i've tried all solutions but without any lucky.
This noise: https://www.dropbox.com/s/tvzqs4ybhayiod2/Screenshot_2013-11-30-08-59-47.png is always present, ALWAYS!
It's repeated continuosly every 10/15 seconds.
I've also tried to move the antenna location at my parent's house....nothing!
This noise was still present.
At this point, i don't know how could it be.
My actual gain is 5*5 and trigger to 65mv but lightning detection is too poor....a near station (Scandicci) detects four times more than mine.
I've no other ideas.
If you would i could give you User and Pass to my Blitzortung panel.
Regards,


Alessandro

[tobi]

This noise: https://www.dropbox.com/s/tvzqs4ybhayiod2/Screenshot_2013-11-30-08-59-47.png is always present, ALWAYS!

This noise comes from the data transmission to the LCD. You can eliminate it, by disabling the whole display ("LCD Auto Off" option in the settings). There are other noise sources which can not be disabled, but their amplitudes are not so high. As long as your threshold values are at least ~100mV, you shouldn't see the noise. There's no need to go much lower here. Such digital noise is an disadvantage of the current piggyback solution with the STM32F4Discovery.

[i_fiorentino]

This noise: https://www.dropbox.com/s/tvzqs4ybhayiod2/Screenshot_2013-11-30-08-59-47.png is always present, ALWAYS!

This noise comes from the data transmission to the LCD. You can eliminate it, by disabling the whole display ("LCD Auto Off" option in the settings). There are other noise sources which can not be disabled, but their amplitudes are not so high. As long as your threshold values are at least ~100mV, you shouldn't see the noise. There's no need to go much lower here. Such digital noise is an disadvantage of the current piggyback solution with the STM32F4Discovery.

Wow, great news!
But if i disable display LCD the amp and antennas still works?
Thanks,

Alessandro

[Cutty Sark Sailor]

But if i disable display LCD the amp and antennas still works?
Thanks,

Alessandro

Sure... they'll work fine. 
Mike

[Cutty Sark Sailor]

Neighbors' Outdoor Flashing Christmas Lights:   Rudolph will probably burn out the system on Christmas Eve....
Be nice if they'd just turn 'em off during daylight every day, also...

[miraculon]

I have been pondering   on whether to request that the Blitzortung guys (Tobi or Egon, not sure who does it) add the "filters" or adjust the thresholds remotely.
I particularly think that I should do this for the "green" 6.8USB system (now running on OpenWrt).
Has anyone requested filters/thresholds from them? How did it work out and what did they do?
I have seen that they added a specific filter for the robot-sheep (lawnmowers) over on the Blitzortung.org forum.

Greg

Update: got an answer back on this. It won't help my situation.

[miraculon]

I had a crazy big noise tonight affecting both RED and USB6.8(Green). The Green system (north end w/ferrites) was far worse. I was able to adjust the gain down a bit on RED (south end with big loops) using my bookmarked "presets".

Here is the Green tracker output (OpenWrt) showing almost rail-to-rail amplitude noise. Even with my adjustable threshold set to >1.5V_pk-pk I couldn't get rid of it (+/-750mV). Then all of a sudden it stopped and I was able to reset the threshold to normal.

Greg

[Cutty Sark Sailor]

It's Holiday time, cold weather, and strange things are happening. I've had similar signals, with a delay difference between A&B channels! Weird. Whatever mine is, I believe it to be ground conduction, for some reason, rather than air, or it's a discharge moving down a power line. Like your's, they're very strong.
I''ve had a couple of days/nights with the amps virtually biased off.

Mike

[miraculon]

I have a LED bulb running on an X10 module. Even though it wasn't dimmed, the AM radio (~530KHz) was buzzing pretty good around a wire in the bedroom where the GREEN is in the closet.
Placing the AM radio close to the LED bulb, it was very strong. However, when I shut it off, the noise on the tracker was unchanged. So "that wasn't it". The mag field was reading higher than normal on the Cornet electro-smog meter during this noise.

I seem to keep finding a lot of "not it" noises....

Greg