Weather Station Hardware > Blitzortung

Interference and Noise

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Cutty Sark Sailor:
'Interference': Any undesired signal that tends to interfere with reception.

I thought it time to start a thread that brings all our noise knowledge into one place, especially to help those living with frustration and those who may be less experienced and knowledgeable. Perhaps we could bring our troubleshooting, isolating, and resolution tips here, along with any screen captures we might grab.

Qualification: June 3 2014 Please Note that this looks at H field only, Amplifier 1, channels A (red) and B (green).  Among other difference between E and H fields amps: You CANNOT DISABLE E-field signals by checking "don't send" on the settings page. The server wants to see all three channels. Best you can do is set gains to 1x1, thresholds to "0". You can adjust gains. E field signals look different, and interference location is a different process.

We all want the clearest signal at the maximum distance that supports the network, and - for myself - there is some 'pride' and curiosity involved. We have healthy servings of those, or we wouldn't get involved it this! Contra-wise, we also want to avoid hindering the network efficiency by ignoring 'nearby' signals... especially as more stations come online in the USA. Our 'long range'  capability becomes less a factor, and clean signals become more important... not ignoring the heavier load on the servers due to mucho 'noise' signals.

The first phase would be to identify, if we can, the type and source of interference. And that becomes quite a chore sometimes.

Addenda, May 2015
...these thoughts:
While communicating with some operators, I developed a sense that some of us might be
confused when we speak of "interference" and "interference".... :D
We might be using "interference" as 'a disturber or noise that degrades communication or data, or a system's operation'.
But we might also simply be referring to "a system going into 'interference' ".

System RED (and BLUE will likely operate in a similar manner) will go into one of two types of "Interference Modes" from time to time.  "Burst" or "Normal"
The System is designed this way, generally,
1. Because nearby active cells produce so many signals, so rapidly, that they cannot normally be recognized separately... and matter of fact, one "paradigm" of the developers might be phrased as "detected signals <30km are generally useless to the network"  with the current design, anyway.
So when you go interference because of nearby storms.... accept it, let 'er ride, and let the network do its net work.  :D
2. Unless you have a perfect location, sporadic 'disturbers' such as an arcing power line, may produce conditional interference that swamps the controller similar to nearby cells, such are useless anyway.  But they're sporadic, and when they cease, you'll come out of interference.
3. Repeating, identical, signals that might be caused by someone standing nearby with walkie-talkie, burst of repeating  power line noise... weird stuff.

Now, while Interference Modes can be triggered by non-lightning signals,  it is based on the "number of signals sent" within certain time frames.
Except for the limited 'repetition and recurring' algorithms for "Burst Mode", it has no recognition of "types of signals" and doesn't care.
Interference mode can be activated due to signals on all channels, or one single channel, or a combination if you're running 5 channels including both H and E field.

It also is one 'controller parameter' that is monitored over time and varied by the server/controller! 
In other words, the server/controller can lower or raise those limits depending on what it sees from your station! 
You only have "indirect control' of this response: your operating mode, gains and thresholds, etc.
The 'basic' purpose is to avoid sending "too many signals" or "EM noise pulses" from your station.

These "interference parameters" operate no matter what mode you're in -Auto or Manual: 

If you look at your 'status' page when you access your controller web interface, down under "other parameters', you see something like this:
Interference Mode
   Burst        When > 80sig/s in 3s average. Disable when 50% below threshold
   Normal     When > 70sig/s in 60s average. Disable when 30% below threshold

...and if too many signals are actually sent under certain conditions,
that will 'back that down' to, for e.g. 30sig and 15sigs.... until
you can come out of interference, and the limits will rise again after some period of time.

So if over "some period of time" you've averaged over 70sigs/minute, you'll go into "Normal" interference, and stay there until it drops below 70sigs average.... which can be a long time... especially if the /controller has lowered the max limit temporarily for your controller to 15...! And if you are in Auto mode it could take even longer under certain conditions, as the controller may continuously cycle on and off and in and out of the mode.

For Burst mode... (short periods of repeating signals) it'll come out of interference much quicker.. a few seconds). It can be longer, again, if your limits have been temporarily lowered...

Burst mode is 'disabled' in events where half the signals are below the trigger threshold, and "Normal" mode  less than 30% below trigger before being 'disabled'.

Remembering that you have only indirect control over 'Interference Mode" ... each channel's 'gain and threshold' settings.
If you're in "Automatic" mode, you have no access to your gains and threshold settings. Unless you desire to wait until the sources vanish on their own, you'll have to return to "Manual" mode, and reapply gain/thresholds settings under each specific amp, (the actual gains /thresholds have been set by "Auto", and they are NOT visible under the AMP settings... that shows you your settings so you must hit apply to reset the "Auto" parameter.
It follows, then, that if H channel A is the one causing the interference, you could back down channel A to 'just under noise trigger level, it will now come out of interference, and channel B  continues its merry way, and A now is of some use also.
You can take it from here.

I'll kick it off with the following posts....


Links to explore:
RFI GUIDE From New Zealand, a PDF... pages 1 through 9 have good info!
Radio Jay Allen's Web Page or Download as PDF A thorough, simple look-see, although aimed at AM broadcast, it's very applicable, and not technical.

Cutty Sark Sailor:
Idealized Waveforms:

System Red Received Examples:

And if we've constructed well, are fortunate, in a good location, with adequate antennas, we should acquire strokes and signals similar right from the start.

But not always....


Cutty Sark Sailor:
Our good old American 60hz:

And it often has other noise mixed with it, in this case from an Acer desktop:

Also signals ride in on it:

And now, we have 60hz, computer leakage, and signals...

But wait!   There's more!   

Moving on to computer noise!

Cutty Sark Sailor:
When we first combine our antennas, amp, and controller, into 'The System',  we may in fact be sitting right next to our pc, laptop or whatever...and our new Blitzortung system  immediately goes into interference, with a signal screen that looks similar to this:

Or the noise might be a lower level, with signals visible:

The above 2 images result from an HP Laptop 5 and 10 feet distant from the antennas.

The below contain interference from a leaky ACER desktop, in another room, 25' away! About 5' from the controller and it's cables:

And here's a signal riding in on it:

Now, take a piece of wire, connect it to the computer case (metal, hopefully) and ground it to the controller!

Well, that was simple enough. Now it may be tolerable.

Now what is this?

At the far right, what appears to be a signal from a streetlight!  Sodium or Mercury vapor?... and they'll put you in interference in a jiffy!

Possible Quick Resolutions: 1) Have you grounded the Controller per the documentation? 2) Move the antenna and amp well away from the computer room if possible! 3) Try grounding the metal PC case. Measure any voltage difference between case and the controller's ground first! Use a high impedance meter...


Cutty Sark Sailor:
Power Lines and stuff (anything that arcs, for example, an insulator, transformer, etc) might look like this:

a flurry of spikes, and that slow '60Hz' or even '120Hz curve'...  probably intermittent... if it's a street light, you'll note it just at dusk when it tries to fire, and sporadically throughout the dark hours, until sometime after sunrise...

It may be riding on other noise:

Any arcing device may look similar... power drills, sanders... etc  etc

Possible Quick Resolutions: 1) If you've isolated it to a street light, the power company, city, or other utility or factory is responsible. In some areas the Property Owner has to make the complaint. Tell 'em there's a street light/security light failing. Could also tell 'em it's interfering with your late night A.M. Talk Radio program reception... You've got the FCC on your side. But not necessarily for lightning detector interference! More importantly, tell 'em if you're pretty sure it's a transformer or insulator... you don't won't to be powerless during cold weather! (Or hot, for that matter)... .



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