How does a StrikeFinder work?

[PeterNSteinmetz]

I had a StrikeFinder in a previous plane but never really understood it more than it picked radio associated with lightning strikes.

Can someone explain how this gadget shows the location of strikes?

 

[rotorwrench]

Can someone explain how this gadget shows the location of strikes?

It works on the same principal as an ADF works in locating an NDB with a loop and sense antenna. In general terms, the strike finder loop antenna detects the direction of the strike by its EMF and the sense antenna fine tunes that direction. But instead of an arrow indicating the direction like on an ADF, the strike finder display shows the lighting strikes as a dot or dots depending on the scale used.

 

[PeterNSteinmetz]

Thanks, that explains direction, but what about distance?

 

[Jim Logajan]

Thanks, that explains direction, but what about distance?

Here are some patents:

US4023408A - Stormscope - Google Patents

A storm mapping system detects electrical activity caused by weather phenomena such as lightning strokes and the like and displays information related to the electrical activity as indicative of storm location with reference to an origin which is taken as the observer's location. A cathode ray...

patents.google.com

US5295072A - Sampled data lightning strike detection and mapping system capable of recovering a pre threshold sample history for detection and mapping processing - Google Patents

A sampled data lightning strike detection and mapping system receives a signal waveform representative of a lightning strike and samples the waveform to generate a train of data samples representative thereof. A data sample of the train is identified as exceeding a predetermined threshold and...

patents.google.com

From the first patent: "The azimuth of the display is indicative of the azimuth of the electrical activity. The distance from the reference location to any illuminated location is a function of the signal strength. Although signal strength is not a precise indicator of distance, it is a useful data item in that the more severe storms generate the maximum signal strengths. In contrast to the prior art systems, the storm mapping system of this invention illuminates a location whose distance from the origin is inversely related to signal strength. In this manner, electrical activity closest to the observer's location is displayed as such."

 

[Jim Logajan]

Just realized both patents are expired and they contain circuit diagrams. DIY lightning detectors anyone?

 

[PeterNSteinmetz]

Interesting idea Jim. What sort of underlying platform would you think to use? Would it qualify under non-certified safety enhancing equipment?

 

[PeterNSteinmetz]

A much simpler version than that required for aviation purposes, but might contain some idea.

Detect Lightning Strikes With An Arduino

Lightning is a powerful and seemingly mysterious force of nature, capable of releasing huge amounts of energy over relatively short times and striking almost at random. Lightning obeys the laws of …

hackaday.com

 

[rotorwrench]

but what about distance?

I believe the strike equipment samples several specific EM frequencies and compares it to a programmed benchmark to determine distance. But I'm not 100% sure.

Would it qualify under non-certified safety enhancing equipment?

You can install anything you want on your aircraft to include your DIY strike indicator. It's how you install it that determines what documentation you will need. Now if you want to sell your DIY indicator to the public for an aircraft thats a different story.

 

[Bob Noel]

I believe the strike equipment samples several specific EM frequencies and compares it to a programmed benchmark to determine distance. But I'm not 100% sure.

That's my understanding... using relative strength of different frequencies, and knowing how much different frequencies are attentuated by the atmosphere, an estimate can be made of distance (albeit a really rough estimate but one that is probably more accurate that just looking at signal strength).

Not perfect, but as I've said at other times, my own use of my strikefinder was more of there-be-dragons, don't go there.