Author Topic: Signal Quality  (Read 1223 times)

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Offline Cutty Sark Sailor

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Signal Quality
« on: July 06, 2014, 06:11:06 PM »
Well, what can I say...?  We'd dropped a few hints in other threads, lately...
Time to pay attention!
Quote
... Some stations which send lots of unusable signals have already been identified. Their signals are just noise or the receiver/amplifier seems to be modified (i.e. tuned system). Those stations have been disabled now, as their signals will falsify the results. There will be a message on the LCD and/or web-interface. After the problem has been solved the owner must contact us and we will enable the station again.
http://forum.blitzortung.org/showthread.php?tid=629
 

Offline JonathanW

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Re: Signal Quality
« Reply #1 on: July 06, 2014, 06:18:24 PM »
Well, what can I say...?  We'd dropped a few hints in other threads, lately...
Time to pay attention!
Quote
... Some stations which send lots of unusable signals have already been identified. Their signals are just noise or the receiver/amplifier seems to be modified (i.e. tuned system). Those stations have been disabled now, as their signals will falsify the results. There will be a message on the LCD and/or web-interface. After the problem has been solved the owner must contact us and we will enable the station again.
http://forum.blitzortung.org/showthread.php?tid=629

Did you see the most recent signals of the guy who complained about his system red being disabled?  That 1-meter loop he's using for H-field looks like it has a maximum received signal somewhere below 15 kHz.

Doubtless great range, but unusable signals.

Offline dfroula

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Re: Signal Quality
« Reply #2 on: July 06, 2014, 08:34:15 PM »
The signals really do look strange. Besides both A and B channels having identical waveforms, the signals seem to "ring" after a lightning impulse hits the antenna/amp, as one would expect if a tuned tank circuit were attached to the amp.

Don
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Offline dfroula

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Re: Signal Quality
« Reply #3 on: July 06, 2014, 08:44:30 PM »
The interesting thing is, this station's strike ratios are quite high, indicating the signals are being used by the servers for locating. Likely, the station is affecting the locating accuracy, and on a high percentage of the detected strikes in Europe, at least until the servers pulled the plug. The signal counts are also quite high.

I guess one of those many peaks must align with a lightning signal somewhere!  :shock:

This station has been of concern for the past year, as the odd signals have been mentioned before by the developers in the forums.

These graphs show the last four days of activity.

Don
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Offline JonathanW

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Re: Signal Quality
« Reply #4 on: July 06, 2014, 08:52:21 PM »
Was there anything mentioned in the forums by some users attaching specially-tuned loops/coils?  Maybe some of the commercially-available "lightning detector" ferrites or loops?

I agree - the signal looks like it's from some sort of high-Q probe, which given the normal input resistor would probably take some doing (unless the input resistor were swapped out, as well).
« Last Edit: July 06, 2014, 08:59:10 PM by n0ym »

Offline dfroula

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Re: Signal Quality
« Reply #5 on: July 06, 2014, 09:04:14 PM »
I'm guessing he removed the damping resistors. Those would normally kill the Q of a tuned circuit, but the resonance could still cause an issue. I suppose the resonance could be caused by a very long cable run from the antenna to the amp, but the low 15 Khz resonance point makes it look like there is an intentional tuning capacitor across the antennas.

I don't believe the manual warns about resonant antennas specifically, other than cautioning about self-resonance and using excessively long connecting wires/twisted wires between the amp and H-field antennas.

What is clear is this guy's station is contributing to, occasionally, over 80% of the detected Region 1 strikes, and degrading the accuracy in the process.

Don
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Offline scarecrow93

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Re: Signal Quality
« Reply #6 on: July 07, 2014, 02:31:59 PM »
Looks like I might have been disabled for some reason. 

No idea why.  Haven't modified anything on either the amp or controller.  I rolled the same ferrites with the extra 50mm length Cutty's has.

Does anyone see anything in my signals that would be a concern?  I've been experimenting with gain a bit and have kept it low just to keep out of interference mode.  I'm trying to find that "set it and forget it" gain setting.

Thanks!
Lance
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#724 - Huntingtown, MD(Aug 2013 - Feb 2014)
Owings, MD(Feb 2014 - Feb 2015)
Annapolis, MD(Late Feb 2015)

Offline Cutty Sark Sailor

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Re: Signal Quality
« Reply #7 on: July 07, 2014, 02:48:54 PM »
Looks like I might have been disabled for some reason. 

No idea why.  Haven't modified anything on either the amp or controller.  I rolled the same ferrites with the extra 50mm length Cutty's has.

Does anyone see anything in my signals that would be a concern?  I've been experimenting with gain a bit and have kept it low just to keep out of interference mode.  I'm trying to find that "set it and forget it" gain setting.

Thanks!
Lance
What's your station number???
 

Offline scarecrow93

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Re: Signal Quality
« Reply #8 on: July 07, 2014, 02:53:58 PM »
724
~Lance
#724 - Huntingtown, MD(Aug 2013 - Feb 2014)
Owings, MD(Feb 2014 - Feb 2015)
Annapolis, MD(Late Feb 2015)

Offline Cutty Sark Sailor

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Re: Signal Quality
« Reply #9 on: July 07, 2014, 03:12:10 PM »
Here, Lance...
http://frankfortweather.us/BoStaSig/
Your signal does have some noise in it... perhaps from a nearby computer, or similar... 
those images should change every 2.5 sec...
Server seems to be rejecting a lot of signals... infrequent image change, in other words...
Mike
« Last Edit: July 14, 2014, 01:12:45 PM by Cutty Sark Sailor »
 

Offline scarecrow93

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Re: Signal Quality
« Reply #10 on: July 07, 2014, 03:18:00 PM »
Thanks for the help Mike!

Lance
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Owings, MD(Feb 2014 - Feb 2015)
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Offline Cutty Sark Sailor

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Re: Signal Quality
« Reply #11 on: July 07, 2014, 03:19:18 PM »
Thanks for the help Mike!

Lance
Your status was showing interference a few moments ago... check your thresholds....
 

Offline Cutty Sark Sailor

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Re: Signal Quality
« Reply #12 on: July 07, 2014, 04:19:35 PM »
Arrggh... guess Egon's doing server work... no indications on sigs/spectrums as which channel signal is being used by server... I miss that... be glad when he gets through adding those quality parameters... .