Listen to the VLF natural radio band. Listen to Whistlers, Tweeks, Auroras, Earthquakes, and other natural events that create VLF radio waves in the range of 100 Hertz - 10000 Hertz.

This 5 transistor VLF receiver will drive a speaker.

The unit allows wide band (untuned) reception and features Hi-Lo tone control switch (SW1).

The unit can be tuned by placing a capacitor across the antenna leads, but this will distort the pleasing sounds of the natural radio waves.

VLF Antenna. Any of our VLF antennas.

Q1, Q2, Q3, Q4, Q5: STORMWISE PART # 2N4124 NPN Transistors.

R1: 3000 ohm resistor. Do not use wire wound type. Adjust value higher or lower for best overall "tone". Lower resistor values cut higher frequencies and general sensitivity. Max value is @ 10 K-ohms.

R2: 47 K-ohm resistor.

R3: 47 K-ohm resistor.

R4: 100 K-ohm resistor.

R5: 1 Meg-ohm resistor.

R6: 470 K-ohm resistor.

R7: 10 Meg-ohm resistor.

R8: 330 ohm resistor.

R9: 330 ohm resistor.

C1: 0.022 uF capacitor.

C2: 10 uF capacitor.

C3: 0.1 uF capacitor.

C4: 0.1 uF capacitor.

C5: 0.1 uF capacitor.

C6: 220 uF capacitor.

SW1: Any pushbutton SPST switch. For tone control.

SW2: Any pushbutton SPST switch. For ON - OFF.

VR1 (part not labled in diagram near speaker). Optional 200 ohm volume control resistor.

SPKR: Any 8 ohm, 12 ohm, or 16 ohm Speaker greater than 3 inches diameter. Use a "mid-range" type Hi-Fi speaker designed for the frequency range of 1000 Hertz through 5000 Hertz. This is the audio frequency range of the tweeks and whistlers.

WARNING! Do NOT use headphone or earphones. Sudden very loud sounds possible.

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

Keep the antenna 12 inches or more away from the speaker or speaker leads. Feedback squeel will result.

Antenna can be located remotely outdoors away from powerline noise by using microphone cable or twisted pair.

Antenna does not need to be up high for good reception. It can be located a few feet above ground level away from power lines.

Operation:

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

Connect all input and output cables.

Apply 9 volts from battery.

If the unit squeels then you forgot to place R1, or the Antenna is too close to the speaker.

Adjust TONE Switch (SW1) as needed for most pleasing sound or signal strength.

Do NOT use headphones or earphones, sudden very loud sound possible.

Rotate antenna for best reception. Keep antenna away from speakers. Sudden LOUD feedback squeeling sound possible!

Whistlers and Tweeks are best heard after 9 PM your local time. Rotate antenna for best results.

Whistlers travel NORTH and SOUTH along the Earth's magnetic field lines so point the ENDS of the ferrite rod antenna EAST and WEST so the flat broadside will pick up.

Tweeks travel EAST and WEST (mostly) so point the ENDS of the ferrite rod antenna NORTH and SOUTH so the flat broadside will pick up.

For best results use a "mid-range" type Hi-Fi speaker designed for the frequency range of 1000 Hertz through 5000 Hertz. This is the audio frequency range of the tweeks and whistlers.

The ionosphere propagation cutoff is approximately 1600 Hertz, which results in the "ping" sound of tweeks. But this cutoff does not mean that nothing can be heard below 1600 Hz. VLF waves can travel through the Earth's soil and underground rivers.

If the antenna is mounted vertically this will allow hearing local underground radio signals (from earthquakes), and eleminate all of the distant lightning static noise, including any tweeks and whistlers.

See antenna directional signal pick up diagram at bottom of this page.

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

You may want to change C1 and C2 depending on the exact tone quaility you prefer.

The receiver will go down to 1 Hertz, but you will have to increase the capacitor values and use many turns of wire (more than 2000) to get there.

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

TUNING DATA

This project is an un-tuned wideband VLF receiver so no tuning capacitor is needed.

These antennas exibit a bi-directional reception pattern as shown above.

Looking down from above with the ends of the antenna pointing North and South, just like a compass would, the directions of best reception are EAST and WEST as shown by the circles in the chart above. There is no signal pickup from the North or South. To pickup from the North and South you would have to point the ends of your antenna to the East and West.

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