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radio for VLF (very low frequencies)

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Experimental receiver for VLF. I received electromagnetic (radio) signals between 14 and 22 KHz with a capacitor of 4,7 NF over the showed coil. The schematic is identical to that of the storm detector IV (with the 6088 Tube), the coil is differently constructed. There is one more transistor amplifying stage + an AM detector (germanium diode) at the end of the extra stage. Input (basis) and output (collector) capacitor to the extra transistor can be between 390 N and 470N. The coil (tank circuit) can receive frequencies between 4,5 KHz and 25 KHz. At 4,5 KHz the capacitor is approx. 20 N (test), at 14-22KHz the capacitor is 4,7 N. Test the resonance of the receiving coil (= received frequency) by connecting an LF generator with a capacitor of approx 50 P to the top of the coil and a scope on a location before the AM detector. Turn the frequency and see where the coil "peaks" with a certain location of the ferrite rod (more in-out).(on the channel of Allamericanfive radio on YouTube there is a clear demonstration of what I mean in the video "resonant frequency"). Coil is 7 x 200 turns 0,1 mm enameled wire, wound in sections of 200 turns, on cardboard tube of approx 1 cm diameter. Ferrite rod must be moved in-out the coil to tune in on the maximum of the received Very Low Frequency. You can see on the scope if you have tuned in well. Turning (changing the direction) of the ferrite coil has a great effect on reception. I don't know where these radiosignals come from (not from computers I presume). The noise you hear on this video was created by my digital camera and received. So I could not get too close. In the showed video one of the 200 turns sections is shortcut, so the effective coil is 6 x 200 turns. If there is interest I will upload the complete schematic.

Channel: Science & Technology
Uploaded: November 30, 1999 at 12:00 am
Author: radioam232

Length: 03:00
Rating: 4.92
Views: 4230

Tags: 14  22  4.5  6088  frequencies  KHZ  low  NL11561  radio  radioam232  receiver  very  VLF  

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Video Comments

radioam232 (November 30, 1999 at 12:00 am)
The project was inspired by an article in an old radio magazine ('60s)that it was possible to hear thunderstorms from far way (and proved to be true).
callieland (November 30, 1999 at 12:00 am)
excuse me boys, i'm no engineer so indulge me. why are you endeavoring to listen to VLF signals?
radioam232 (November 30, 1999 at 12:00 am)
It is a kodak easyshare Z 740. All digital cameras like to eat batteries. So a 1700 mAHour is a good choice.
gccengineering1996 (November 30, 1999 at 12:00 am)
What model number of the camera do you have? I have camera model C340 and the digital camera is a battery guzzler. I just put in 2 new batteries and right now the batteries are dead. What batterie would you recommend for making long videos for radio?
radioam232 (November 30, 1999 at 12:00 am)
Indeed the camera (Kodak digital camera) makes radiofrequent noise. Did not know that untill I approached the VLF antenna. The noise field is approx 30-40 cm around the camera.
gccengineering1996 (November 30, 1999 at 12:00 am)
cool sounds good. I see that there is noise from the camera cause the camera is emitting RF energy, possibly the reason why I cannot make a video listening to LW without making noise. I will keep on watching your videos and learn more.
radioam232 (November 30, 1999 at 12:00 am)
its on a series on my channel, all about building a storm detector.
gccengineering1996 (November 30, 1999 at 12:00 am)
Does this cover 1kHz to 20 kHz? Most of that activity is Natural Radio. Is there a circuit diagram for this circuit so I can start planning out this project soon?
radioam232 (November 30, 1999 at 12:00 am)
Thank you! Wish you luck, i find it very interesting, for me it is also an unknown frequency range.
XRayCam (November 30, 1999 at 12:00 am)
Thanks......wonderful radio. I am just getting started into ELF/VLF radio listening :)

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