2014-08-10, 14:34 (This post was last modified: 2014-08-10, 14:37 by Jonathan.Williams.)
(2014-08-10, 11:16)Ross.Wheeler Wrote: Detecting lightning within a certain radius of a location, with a single receiver, is almost impossible.
Lightning strikes are of various intensities. Some are small, (relatively) low current discharges, others are massive discharges which produce very powerful radio frequency signals.
How a single point station can possibly discriminate between the two eludes me. It clealy also eludes a great many other technical minds!
The only two ways I know of require a significant number of stations operating co-operatively.
Method 1 requires each station to use two antennas and to produce a direction and time. Somewhere, these directions (and time signatures) are merged to determine where the strike was.
Method 2 requires each station to precisely time-stamp the signal, and a co-operative system that analyses the signals to work out where the source must have been to satisfy all the measured signals.
Method 2 is what Blitzortung uses - a "Time-of-Arival" (TOR) system. It is simple in concept but complex in implementation and requires a significant investment in hardware and processing power.
A simple receiver plus threshold detector may tell you that there is lightning "somewhere within the receiving area", that area may be several thousand miles, and without discrimination, will almost certainly count every electrical circuit opening or closing, every arcing contact, every breaking down insulator, withing a great distance from your (single) receiver.
There is at least one study (Stanford?) that found lightning produces a typical signal, and the nature of the signal varies with distance due to phase velocity characteristics.
Anyway, I would not be surprised if, for BO stations that use H-field coils that are properly set up at right angles to one another, some direction finding is also possible (see the X-Y plots on lightningmaps.org). Given the variation in coil design, it's probably not as accurate for DF'ing as, say, the systems used in Lightning Radar or (ex-) Vaisala's National Lightning Detection Network, but since typical BO stations probably don't change configuration very often, it might at least be useful for elimination of some false positives.
Quote:Detecting lightning within a certain radius of a location, with a single receiver, is almost impossible.
Lie!
Boltek's are single receiver's, and for beeing that and taking that in act, damn accurate if they are calibrated correctly
The Boltek is still only an educated guess. Yes, you can calibrate them, but they will still be subject to a large degree of inaccuracy - from those I've spoken to about their operation anyway. Yes, they probably give you a useful guess. No, they don't give you an accurate or reliable distance.
(2014-08-10, 14:34)Jonathan.Williams Wrote: There is at least one study (Stanford?) that found lightning produces a typical signal, and the nature of the signal varies with distance due to phase velocity characteristics.
Yes, but that will require quite a lot of computational power, which the OP specifically wasn't going to be using.
(2014-08-10, 14:34)Jonathan.Williams Wrote: Anyway, I would not be surprised if, for BO stations that use H-field coils that are properly set up at right angles to one another, some direction finding is also possible (see the X-Y plots on lightningmaps.org).
Yes, and it's quite accurate. While I was commissioning my first station, I used this to determine the source of some interference, by taking my sensor and a laptop and taking a few readings from different locations.
Even so, using DF will require multiple stations. If you're lucky, just two, but there will inevitably be lightning along the axis of those two resulting in no solution, and a third would be necessary. Again, it's not just using the receiver and plonking a counter on the output!
Just to clarify - yes, I agree a single receiver can certainly tell you if there's lightning-like activity around.
I was saying that a single receiver of the kind suggested (a BO amplifier with no external computing) cannot reliably discriminate between
noise or lightning, and cannot accurately be set to only pick up lightning with a (say) 50km radius (ignoring lighting >50km).
Yes, precision analysis of the waveform might give you enough additional information to make a reasonable estimate of distance under many (even most) atmospheric conditions, but that is not the configuration requested by the OP (which I thought would be a given in the context)
2014-08-10, 22:33 (This post was last modified: 2014-08-10, 22:34 by Jonathan.Williams.)
(2014-08-10, 22:20)Ross.Wheeler Wrote: Yes, and it's quite accurate. While I was commissioning my first station, I used this to determine the source of some interference, by taking my sensor and a laptop and taking a few readings from different locations.
Even so, using DF will require multiple stations. If you're lucky, just two, but there will inevitably be lightning along the axis of those two resulting in no solution, and a third would be necessary. Again, it's not just using the receiver and plonking a counter on the output!
Just to clarify - yes, I agree a single receiver can certainly tell you if there's lightning-like activity around.
I was saying that a single receiver of the kind suggested (a BO amplifier with no external computing) cannot reliably discriminate between
noise or lightning, and cannot accurately be set to only pick up lightning with a (say) 50km radius (ignoring lighting >50km).
Yes, precision analysis of the waveform might give you enough additional information to make a reasonable estimate of distance under many (even most) atmospheric conditions, but that is not the configuration requested by the OP (which I thought would be a given in the context)
I absolutely agree. I just thought the thread had brought up some interesting points. I don't think they'll help the OP, though. Frankly, if you're going to put the time and effort into assembling an amplifier and are interested in lightning detection, you might as well save your pennies, build the controller, join the network, and get all the frills
use an analog comparator, set certain threshold to trigger an impulse, calculate the strike ratio and store it in database - that was my original idea.
The amplifier circut is fairly easy, worth givin it a try
(2014-08-11, 01:02)piotreeek Wrote: calculate the strike ratio
But that's the point... the amplifier itself has no concept of "strikes". It's just noise. It can't tell an electric fence or loose connection in a switchboard, or flashover at an insulator, or a motorcar with crook plug leads.... from a real lightning strike.
All you're doing is measuring "how much impulse noise is there now?"
If that's enough for you, great. But "impulse noise" != "lightning activity"
