All that a stormscope can do is receive the EM burst from the strike, use ADF methods to get the azimuth, and have a wild guess at the range using the intensity plus some (according to a Goodrich claim) fudge factor derived from the signal spectrum, which I don’t understand because all the frequencies are going to travel at the same speed and, on a line of sight, are going to be equally attenuated.
Goodrich are believed to have (or have bought) some patents in this area so maybe there is something in there…
on a line of sight, are going to be equally attenuated
Sticking ‘atmospheric attenuation of frequency’ into google images gives several graphs to suggest that’s not so. Particularly in a damp atmosphere.
Particularly in a damp atmosphere.
Yes, but all the interesting absorption effects start at the GHz range, while the lightning spectrum lies in the double digit kHz! So about 4 orders of magnitude in between.
Well AFAIK short (length wise) intercloud strikes can reach up to the single digit MHz, but AFAIK aviation stormscope can’t receive them.
So stormscopes measure the intesity of the arriving strike, and compare it to some “normative strike” to calculate the distance. Too bad if the actual strike didn’t comply to the “normative strike”.
My guess is that the fudge factor doesn’t come from different frequency attenuations, but they likely try to infer from the look of the time domain waveform how strong the original lightning was.
That’s why time of arrival methods like Blitzortung are vastly superior, IMO.
So I personally would (actually have) rather invest my money into a sat link to access blitzortung than to retrofit a stormscope. And that saves weight too.
Blitz used to support an API and I used to have a little prog (Lview) which gave me the image on my desktop (winXP). A few years ago that stopped, and the man said it was too much bother supporting it.
I wonder if one could transmit the short messages using some sort of “below noise floor” method, at GHz frequencies, and covering all of Europe? 
Satcomms is either expensive or unreliable or both.
f I remember it’s more of a distance based calculation based on the electromagnetic H and electrostatic E field computation. Maxwell theory…I believe..
Maxwell theory…I believe..
That’s what we’re talking about. Problem is, from the received signal strength, you can either work out the distance or the original signal strength at the source (lightning), but not both. So since you want the distance, you need to make assumptions about the original signal strength. And these guesses are not very reliable.
Satcomms is either expensive or unreliable or both.
And we’re having this discussion because stormscopes are cheap and reliable
I must be doing something wrong with the thuraya phone, because so far it worked pretty well – ah yes I’m not using a Lenovo laptop from the last decade
Yes, but all the interesting absorption effects start at the GHz range, while the lightning spectrum lies in the double digit kHz! So about 4 orders of magnitude in between.
You still hear lightning strikes on an FM radio – the bulk of the power may be in the KHz but not all of it. There was still a fair amount of attenuation at the FM frequencies – 100MHz or so.
This report shows that the lightning spectrum at 100MHz is some 70dB down.
So yes, you can hear it in FM radio if the strike is close and the station weak, but you don’t need a stormscope to locate a strike hitting a few 100m away from you! You need a stormscope to locate strikes far away, where those highly attenuated parts of the waveform aren’t useful. Furthermore, the receive antenna will further attenuate these very high frequency parts.
Also, even 100MHz is well below the interesting atmospheric absorption above several GHz.
Low frequency it is then:
http://www.google.com/patents/US5263368
