Author Topic: Should I balance out noise floor readings between loops?  (Read 285 times)

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Offline cbh3

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Should I balance out noise floor readings between loops?
« on: April 02, 2017, 10:35:54 AM »
According to my Blue unit's data, I have a noise floor difference between my two 1 meter H-field loops of about 7-10mVpp.

Should I try to balance this out by adjusting the gain on one of the amplifier channels, or will that throw off the calculations in some way?

Ideally you would want the same noise floor for booth loops when taking a measurement, correct?
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Offline Cutty Sark Sailor

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Re: Should I balance out noise floor readings between loops?
« Reply #1 on: April 02, 2017, 11:12:17 AM »
not really... all you want is a signal out that is twice whatever your noise floor is... if you're running 40mv basement, just don't trigger that low.. trigger at a level at least 85 and set to 'ingnore' 10% below....the last paradigm Egon mentioned regarding this was a server algorithm working " if  signal NOT at least twice the noise level, ignore it"
This is NOT about pure audio... this is Burst Impulse Broad band energy... the 'frequencies' energy is still there... the noise is just that.. noise. I'd suggest any basement around 20-60 mv is fine. If it's much above 40 average, reduce your gains! Or downsize antennas!  We're talking about the signal "grass' here, not spurious signals... The Noise is NOT disturber pulses coming from motors etc, those are 'signals' but you could count 'em as 'basement'level if they're consistently there, and set stuff to match their strength.
To state the obvious... if your basement is at 40 db and you continuously send signals that are only 70 db, you're wasting time, bandwidth, server time for 'useless' data. Which is why folks will complain that 'I registered the stroke, but the server didn't recognized it and I didn't get credit'.... or similar queries........
That 'response' is based on the 'discharge' impulse strength... and I believe it relates to the 83% level of the signal max.  That is, your '83%" peak energy must be "Twice" the noise basement. Once the server has allowed what's supposed to be the discharge pulse into time-stamp processing, the remaining pulse groups of that sferic will be analyzed for 4 or so iterations of  a "Zero Crossing" algorithm for TOGA computation. even though they may be significantly lower than the Discharge impulse. even if 'amplitude wise' they're buried in the nose basement.... the frequencies involved are still retrievable. So, if you've triggered on a signal further away than about 50 miles, you didn't trigger on the true discharge impulse, but a reflection of it.... and at that distance the group crossing pulses may be too weak and distorted to be processed cleanly, though the server will try manfully to 'filter' them out of the noise. So your signal isn't necessarly computed with TOGA, just the TOA of the reflected pulse,... which leads to big deviation circles...
Normal to have DC offsets, and variations in noise levels between channels... but not significant unless totally ridiculous.
In other words, don't out-think or over analyze 'the grass'...


« Last Edit: April 02, 2017, 11:16:40 AM by Cutty Sark Sailor »

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Offline cbh3

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Re: Should I balance out noise floor readings between loops?
« Reply #2 on: April 02, 2017, 11:24:51 AM »
Great background. Thanks for the detail!

I'll continue to enjoy my 25mV noise floor (for now) with my 10*10 gains and 120mV triggers, without worrying about that small difference between the two loops. Good to know how the server works too in the processing when thinking about what we're sending.

Now today it's on with figuring out what kind of E-field antenna to build! I've found some threads in various places and am getting ready to read them all.
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Offline Cutty Sark Sailor

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Re: Should I balance out noise floor readings between loops?
« Reply #3 on: April 02, 2017, 11:37:16 AM »
Great background. Thanks for the detail!

I'll continue to enjoy my 25mV noise floor (for now) with my 10*10 gains and 120mV triggers, without worrying about that small difference between the two loops. Good to know how the server works too in the processing when thinking about what we're sending.

Now today it's on with figuring out what kind of E-field antenna to build! I've found some threads in various places and am getting ready to read them all.
Those parameters are quire typical... 25 is great.. my systems are more like 40
You can use a beverage can pull tab for an E probe If you want..
Just take a piece of wire about 5-10 inches long, stick it in the inboard terminal (outboard is ground) connect your coax, hang that bugger at least a couple of meters above ground as far from structures, noise makers, etc as possible.(mine is 23 feet)... DO NOT connect any ground of any type other than the coax which supplies power, to the E field preamp... the 'air space' between the probe and Earth is critical... don't short it out!... and let 'er rip.  The E field is VERY sensitive... your settings will be more like 4*2 or even 2*2.  It also is NOT designed for distant detecting.. it's usage should be for nearer sferics... originally they wanted to specify 300KM ( about 200 miles)
« Last Edit: April 02, 2017, 11:39:05 AM by Cutty Sark Sailor »

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Offline cbh3

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Re: Should I balance out noise floor readings between loops?
« Reply #4 on: April 02, 2017, 11:44:12 AM »
Good deal. I put a 5" wire on the it and have it in the garage currently, just to make sure it worked and the unit was seeing it operate. I'll be moving it outside and using something a little longer, if I can find the right spot. Maybe today. I will keep it dialed down to be used for close distances. Will be interesting to see how all of this operates when storms actually come through West Michigan vs. just far away sensing.
WU: KROCKF4 || CWOP: C9861 || CoCoRaHS: MI-KN-83 || Blitzotung: 1737
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