Lightning Detection Receiver circuit project

lightning detection radio receiver

There is no technical help with the projects. This circuit is shown as an educational example only.

This lightning detector built on a piece of wood uses only 2 transistors but will detect lightning strikes over 100 miles away.

The antenna works INDOORS - it does not need to be mounted outdoors.

It uses our directional lightning detection antenna part # D6T-3KC-BC or part # AF4T-0.1H-2K-BC-EB as the sensing element.

An audio amplifier connected to the output will emit loud click sound for each lightning strike detected. When severe storms are approaching, this receiver will go crazy - producing hundreds of clicks per minute.

A signal meter can be added in a similar manner to the one in project # 10. This addition also would allow driving a buzzer.

This is a direct detection amplified "crystal" radio receiver. It does not generate RFI or use regeneration. It has no AGC circuit or noise-blanker, making it excellent for research applications.

This radio will drive any common audio amplifier (like the Radio Shack mini-amp) loudly to room-filling volume.

Power the detector with a 9 volt battery. It draws little power so it will run for a long time. The Radio Shack audio amplifier will also run a long time (about 2 months) on a 6-volt rechargeable lantern battery.

Power the detector and audio amplifier only with battery power to prevent AC power buzz noise and pick up of noise.


There is no technical help with the projects. This circuit is shown as an educational example only.

The parts and values are shown on the diagram above on this page. Standard values used. General parts available at any electronics store. Antenna and tuning capacitor available here at WWW.STORMWISE.COM

Antenna is our part # D6T-3KC-BC lightning detection antenna or use part # AF4T-0.1H-2K-BC-EB which has greater sensitivity.

The transistors Q1 and Q2 are NPN transistors 2N3904.

All transistors are available from Radio Shack stores or other electronics parts store.

RX1 is 1 K ohms. If detection range is too great then use a 10 K-ohm resistor. A variable resistor ( 0 to 50 K-ohms ) can be used to adjust the detection range if desired here.

IMPORTANT NOTE: If using antenna D6T-3KC-BC then C1X is 0.047 uF. This capacitor tunes the antenna to approximately 3 KHz, the lightning detection band center. Check frequency of lightning detector, it should not be lower than 2.5 KHz or higher than 3.5 KHz. Adjust capacitor value accordingly if the frequency is out of range. The parts values in circuit design shown were selected for the specific frequency range.

IMPORTANT NOTE: If using antenna AF4T-0.1H-2K-BC-EB then C1X = 100 pF to tune to @ 2.2 KHz. Do NOT tune below 1.6 KHz, as this is the ionospheric cut off. Range will be very limited below 1.6 KHz.

R2X is a resistor of 10 meg ohms down to 2 meg ohms. This value controls the sensitivity. Detector will work fine without it, but with an adjustable resistor you can set the range from local to distant. Without the resistor the range is about 50 to 75 miles. With the resistor the range will be much greater. Resistor should not be less than 2 meg ohms. Try a 5 meg ohms resistor for RX2.

How to build it: Print out the above circuit diagram. Scale it down on your printer or photoshop program so that it is the right size, large enough for the electronic parts to fit the dots. This size is about 6 and 1/8th inches long and 2 and 1/2 inches wide.

Do not leave out or bypass any of the parts, all parts have a required function.

How to build: See photos below on this page.

Obtain some safety goggles, you'll be soldering and hammering nails and cutting a piece of wood (use a hand saw only). Solder is molten metal and can spatter into your eyes. Do not solder without full eye protection.

A 30 watt soldering iron was used.

If you are not familiar with soldering practices, then it -IS- possible to use wire-wrap methods to build the receiver. You can also build the receiver on a solderless breadboard. Ask at Radio Shack store for this item. You'll need the one with the grounded shield base, receiver -will- oscillate on these if not connected to the shield base. You will still need the safety goggles when clipping part's leads or working with the wires.

A square piece of wood should be obtained that is slightly larger than your print-out.

Obtain some copper plated weather-strip nails from the local hardware store. Cut out the paper circuit diagram print-out and tack it to the wood, one tack going into each dot in the diagram. Place the parts on the tacks. Solder parts to the tacks. Make sure tacks do not short to ground shield except where indicated.

Place the transistors last after all the other parts have been soldered, to prevent static damage or heat damage. It is best to just let the transistor sit on top of the tacks and solder it to the top of the tacks with a small drop of solder. Do not bend the transistor's leads too much.

Parts may contain LEAD or other chemicals so wash hands after handling. Solder contains LEAD or other chemicals so wash hands after handling.

There is no technical help with the projects. This circuit is shown as an educational example only.

The output audio signal is over 0.7 volt, enough to drive a small audio amplifier very loudly. Use Radio Shack's Mini Amp, Radio Shack part number 277-1008C.

You should easily detect lightning from thunderstorms over 100 miles away with this unit.

There is no technical help with the projects. This circuit is shown as an educational example only.

The antenna should not be placed more than 10 feet away from the receiver. The antenna works indoors and does not need to be high up to work. Try it at ground level then try it up high - not much difference!

Don't place antenna near speaker! VERY LOUD SQUEELING SOUND WILL OCCUR!

The antenna is directional so rotate the antenna for best reception. If storms usually move in from the West then point the end of the antenna to the North. It is bi-directional with 2 null points. You can locate the direction of the storms by finding the point with the most / least clicks per minute.

Certianly a PC board can be etched and the receiver built that way, for those who are advanced, but the wood way works great for beginners so it's up to you.

Testing and modifications

Try the detector out during the day and at night. Make note of the ranges to the storms. Range will be better at night.

There is no technical help with the projects. This circuit is shown as an educational example only.

The transistors we used had an hfe gain of about 325. Gain can vary between 150 to 370 for different transistors. This can affect sensitivity, but don't worry, adjustment of parts values can fully compensate to give the super long range you want:

If range is too low both day and night then try the following:

Add in another 10 meg resistor in the 20 meg resistor chain in the 2nd RF amplifier, for a total of 30 meg ohms. This will increase sensitivity.

The unit has a "squelch effect", caused by the 2nd RF amp's biasing levels and by adjusting the resistor values (20 meg and R2X) will bring the squelch level down so that lower intensity strikes are able to be detected. Also some low level hum noise may begin to be heard, so don't adjust it too low! RX2 should not be less than 2 meg ohms.

Do you Want to listen to what the receiver hears? Then just bypass the 4 diodes in the output. You'll hear all of the 3 KHz lightning strikes plus any background noise coming in.

Also note that the unit will be more sensitive at 6 volts than if powered at 9 volts, for a given parts value (battery voltage affects the squelch level, the detector becomes slightly more sensitive as the battery voltage drops). You can run both the detector and the amplifier off of the same 6-volt 4-amp hour rechargeable lantern battery for quite a while. Keep the antenna away from the speaker - loud squeel sound will occur.

Do not allow the wood to become moist or damp - This can affect sensitivity due to stray resistance through the wood due to moisture. Build on a standard circuit board to prevent this. When used indoors in normal humidity, moisture is not a concern.

Copyright 2011
All rights reserved