Topic: Red board, auto gain control

[DaleReid]

Shielded cable arrived, and I went to the local ShopKo, sort of a mini-Walmart and got a clear plastic storage box that the ferrites fit into nicely and relatively water proof, and just took the whole contraption about 20' out onto my deck.

Now I see that the gain settings are bouncing up, from 800 to even 2000 at times, but the noise floors are still in the 40-80 range.

I assume Red knows what its doing, and that by adjusting the gain up it has confidence that the signals it is analyzing are more manageable, at least when it comes to adjusting the gain upwards. 

Is that a true statement?

Also, what sort of noise floors is one hoping for?  Zero?  I would assume the lower the better, but even with the noise being slightly less than it was, Red is whomping up the gain.  What parameter, if not noise, is it using to do these changes?

Dale

[dfroula]

After taking care of any obvious noise issues and proper grounding, I do the following (assuming no nearby storms):

Put system in "manual" mode.

Turn off auto-noise adjustment. You may need to reboot before the controller will accept new manual gain settings after disabling the feature.

Set threshold to default of 120mv.

Experimentally, figure the maximum gain that will keep the unit out of interference. Be sure to use the combination of first/second stage gains that results in the final desired gain with the first stage number higher than the second. Several gain settings have multiple combinations that achieve the same overall gain. It is always best to put the highest gain in the first stage, before any filters.

Back down the manual gain one adjustment level from the highest gain determined above.

Re-enable auto-noise adjust. The system will reduce the threshold and adjust the "effective gain" to compensate for variations in the local noise floor. The gain and thresholds you set manually establish a limit beyond which the algorithm will not adjust. The system can increase the channel sensitivity by either reducing the threshold or increasing the actual gains. The percentages shown on the status page are the percentages of the maximum gain you set manually.

"Effective Gain" is normalized to a 100 mv threshold. The "effective gain" = (100/threshold in mv) * (GainA) * (GainB).

So, if you manually set the threshold to 120mV, GainA to 10 and GainB to 8, the "effective gain is (100/120 * 10 * 8 ) = 66.66 rather than 10 * 8 - 80. The percentages on the status page are referenced to this number and will never exceed those "effective gains".

I hope this makes sense!

Regards,

Don
WD9DMP

[miraculon]

Shielded cable arrived, and I went to the local ShopKo, sort of a mini-Walmart and got a clear plastic storage box that the ferrites fit into nicely and relatively water proof, and just took the whole contraption about 20' out onto my deck.

Now I see that the gain settings are bouncing up, from 800 to even 2000 at times, but the noise floors are still in the 40-80 range.

I assume Red knows what its doing, and that by adjusting the gain up it has confidence that the signals it is analyzing are more manageable, at least when it comes to adjusting the gain upwards. 

Is that a true statement?

Also, what sort of noise floors is one hoping for?  Zero?  I would assume the lower the better, but even with the noise being slightly less than it was, Red is whomping up the gain.  What parameter, if not noise, is it using to do these changes?

Dale

Since I moved to Rogers City (with a better noise environment) I have been seeing <20mV noise floor regularly. RED is down right now, I need to move it out to the garage and do some wiring, but when I had the "lash-up" running in the bedroom I was seeing mV in the teens.

Greg

[Dr Obbins]

With the station pretty well dialed in, I have the settings for both channel "A" & "B" set at 32*2*40 and the threshold at 100 & 80. The first half of these graphs is showing these settings with the "Adapt to Noise" unchecked. Then at around 10:15 I turned on the "Adapt to Noise" and you can see the results.

Looking at the Cave City count per hour in the second graph at ~03:15, the station was sending over 24,000 count per hour compared to ~350 Whole Stroke Count in the top graph. Does this mean the station was sending ~23,650 bad signals (noise) to the central system?

Now after the "Adapt to Noise" is turned on, it is more in line with the Mean Signals Per Station in the bottom graph, but is missing 40-50% of strokes in the top graph that it would have picked up with the "Adapt to Noise" turned off.

Which is a better situation for the project as a whole?
Picking up many more signals, including many bad, or less signals but better quality?

[DaleReid]

Doc,
Where you getting those graphs from?  I've been through all the places I can seem to find, and nothing like this is being shown for my grabbing? 

Are you generating them from a raw data download, or are they out there on the Blitz site and I've just not uncovered them?  Dale

[Dr Obbins]

Just choose your station from the drop down menu.

[DaleReid]

That's very odd.  I didn't even know there was a

lightningmaps.org 

page.

I always went where the documentation mentioned, which was

blitzortung.org and followed from there.


The things you learn!

Thanks for the lead.  A whole bunch of info about my station that I didn't find on the members/contributor's page, or if it is there not obvious enough for me to latch onto it.

Thanks again for sharing, glad I asked.