GW7ERI AMATEUR RADIO

Tutshill - Chepstow - Monmouthshire

 

Home Made Lightning Detectors

 

 

 

 

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Some time ago whilst surfing the web I stumbled across an excellent website written for electronics hobbyists. The construction projects on this site, http://www.techlib.com/ are the work of Charles Wenzel, and I thank him for making his circuits available.

As I have an interest in both Ham Radio and Weather events, I was particularly taken with his designs for home made lightning detectors, and I decided to have a go.  

The circuits for the lightning detectors can be found at http://www.techlib.com/electronics/lightning.html along with construction notes and readers versions.

The detectors are direct conversion AM (Amplitude Modulation) radio receivers, which are tuned to receive on a frequency of 300 Kilohertz (Khz.)

 When a lightning strike occurs, a radio wave 'pulse' is generated across a wide spectrum of radio frequencies. This static electricity burst can be heard on domestic broadcast receivers tuned to the AM broadcast band.

The radio captures the static burst (pulse) and amplifies it to an extent that the pulse can be used to drive a number of user options, including flashing a lamp or sounding a buzzer. Thus if lightning is present in the atmosphere the detector provides advanced warning of a storm event. As the storm gets closer, the frequency of the pulses increase, therefore it is possible to tell if a storm is approaching or moving away.

I also have an interest in 1920's 1930's vintage radio equipment, and my first detector was designed to mimic this vintage look.

 

The coil holder is an authentic piece from the 1920's, and the coil former is a spider's web type which I made from an old compact disk wound with enameled copper wire. The number of turns is calculated to tune to 300Khz when used in conjunction with the specified inductors in the circuit.

I had good results using a 2 meter band vhf 'rubber duck' type antenna.

 

Inspired by the performance of the 'prototype,' I decided to build the improved version from the circuit detailed on the Techlib site

 

I wanted to observe any increase in the number, or intensity, of storms over time, so I decided to modify the design above by adding a 'Pulse Counter Module' to the Pulse output in the circuit. I also built into the circuit the 'meter' and 'lamp' options (see techlib web site,) then added a buzzer for audible warning.  

    

The circuit was built onto matrix board, and the case was then drilled and assembled. I added a reset switch so I can set the counter to zero as required. The front panel lettering was achieved by using 'transfer' paper printed by an Epson inkjet printer and sealed with spray lacquer.

The detector is reset each morning at 0900 and a record is kept of the number of static pulses which have been detected. I am hoping over time to compare the atmospheric noise levels on a year by year basis.

The final stage was to mount an outside antenna. I used a 2 meter band 5/8 whip.

Overall I am very happy with the performance of both of the detectors, which compare favorably with the data displayed at http://blitzortung.org web site.

The Blitzortung live lightning data can be seen on my Blitzortung Lightning page in the Weather section.