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Old 6th May 2020, 6:49 pm   #1
Chris55000
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Default VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

Hi!

Can any Member find me any construction plans for, or kit of parts to build, a V.L.F. receiver to pick up atmospheric noise, sferics, "whistlers", the "terrestrial dawn chorus", etc?

Chris Williams
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Old 6th May 2020, 8:14 pm   #2
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

Try the mic buffer here http://www.techlib.com/electronics/VLFwhistle.htm on a soundcard or mic jack on a portable device.
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Old 6th May 2020, 8:34 pm   #3
Philips210
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Default Re: VLF Receiver for Steroids, Whistlers, Dawn Chorus, etc?

Hi.

It's worth a look on the Techlib website, particularly here http://www.techlib.com/electronics/VLFwhistle.htm There are a number of different circuits there.

I built the VLF receiver featured in Practical Electronics, October 1979 but haven't tested it yet as I need to build the associated aerial. I will get around to that hopefully this year. PE magazines can be found on the ARH website.

Another interesting project which I hope to build was in EPE magazine, April 2003. That was an Atmospherics Monitor. This can again be found on ARH.

Regards,
Symon

EDIT: MM beat me to it with the Techlib link
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Old 7th May 2020, 12:12 am   #4
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

I'm sure there was another VLF receiver in PE in the 60s but I can't remember which issue. Couldn't find it in a quick look on the ARH site but I'll check in the morning.

Keith
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Old 7th May 2020, 1:20 am   #5
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

I have a vague memory of it being called something like 'Whistler receiver' or something similar.

Like wise, using those terms on the ARH site didn't turn up anything either.

Found it - Practical Electronics September 1968 "Whistler Receiver"
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Old 7th May 2020, 1:32 am   #6
Terry_VK5TM
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

As usual got sidetracked by this thread:-

Googling 'vlf whistler receiver' gives a lot of hits, a couple or three examples:

http://asv.org.au/downloads/RAS/Whis...on-Issue_1.pdf

http://www.radio-astronomy.org/pdf/q...tler-proof.pdf

https://web.archive.org/web/20080601...m/project5.htm
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Old 7th May 2020, 8:17 am   #7
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

Quote:
Originally Posted by Terry_VK5TM View Post
I have a vague memory of it being called something like 'Whistler receiver' or something similar.

Like wise, using those terms on the ARH site didn't turn up anything either.

Found it - Practical Electronics September 1968 "Whistler Receiver"
That's the one. There was also an article on VLF phenomena in the previous issue.

Keith
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Old 7th May 2020, 9:32 am   #8
Philips210
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

Quote:
Originally Posted by KeithsTV View Post
Quote:
Originally Posted by Terry_VK5TM View Post
I have a vague memory of it being called something like 'Whistler receiver' or something similar.

Like wise, using those terms on the ARH site didn't turn up anything either.

Found it - Practical Electronics September 1968 "Whistler Receiver"
That's the one. There was also an article on VLF phenomena in the previous issue.

Keith
Hi

In the PE VLF receiver of October 1979 that I mentioned in post #3 there was also coverage of the VLF phenomena in the September issue too.

Regards,
Symon
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Old 7th May 2020, 10:03 am   #9
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

This thread reminded me that I have one of the old Palomar VLF converters, must find it and see if it still works. I will read the above articles to see what sort of sounds are out there and what antennas get used.

Adrian
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Old 7th May 2020, 10:05 am   #10
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

I wonder if it would be worth experimenting with a 'negative capacitor' circuit for the receiver input. I made a receiver like this many years ago for a research project at work. The negative capacitor replaces the big (narrowband) inductor used in some VLF receiver designs. This allows broadband operation from <1kHz through to the MW band and the antenna element is just a few inches long. The idea is to adjust the small negative capacitance to (almost) cancel any capacitance in the antenna element.
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Old 7th May 2020, 12:05 pm   #11
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

I wonder if things are clearer dowm there.... below the clock rate of SMPS?

David
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Old 7th May 2020, 1:02 pm   #12
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

Back in the late 1970s a work mate built an amplifier with germanium transistors and connected it to a pair of pegs in the ground.
One weekend he brought it to me and I shoved an audio sweep oscillator and amplifier onto a mains transformer in step up mode and fed it into the ground with about 20 feet of spacing between the probes.
We got the signal to go about a mile.
The ground pegs on the receiver was to some extent directional.
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Old 7th May 2020, 2:29 pm   #13
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

Did the idea come from the power buzzer amplifier combinations used for Morse ground signalling in WW1 ? These covered a similar distance (dependant on soil conditions.
Mike.
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Old 7th May 2020, 9:07 pm   #14
Philips210
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

Hi.

A few pics attached of my VLF Receiver (PE October 1979). Note the CA3140E op amp on a skew angle. This was a temporary measure as the PCB is intended for the 'T' version (transistor style metal can). I'll replace the plastic package version for the correct type when one becomes available.

I did a work around on the three pot cores for the mains frequency filter as the original pot cores weren't obtainable.

The little audio amplifier IC that drives the headphones is an odd one. It's a Motorola MC3360P and I amazingly found one amongst my stock of junk. I remembered where it originally came from. It was from an Everday Electronics BFO type metal detector project (late 1977) by FG Rayer. This could easily be updated for a more current style chip no doubt.

The aerial looks straightforward to build using a multicore screened cable. A junction box allows the 'windings' to be made by looping the wires together in sequence to form a multiturn coil. I hope to build the aerial and test out the complete set up before too long. Time is the problem these days though.

Regards,
Symon
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Old 8th May 2020, 1:10 am   #15
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

Quote:
Originally Posted by Gridiron View Post
Did the idea come from the power buzzer amplifier combinations used for Morse ground signalling in WW1 ? These covered a similar distance (dependant on soil conditions.
Mike.
I am not sure what the guy was listening for.
What he built was most likely from germanium transistors. He never showed me a circuit diagram but I guessed it would be no more than an audio amplifier and set up my test signal and let him listen for it.
He was duly impressed especially when I proved to him that putting just two probes into the ground gave a directional result.
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Old 8th May 2020, 11:38 pm   #16
JohnBG8JMB
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Default Re: VLF Receiver for Sferics, Whistlers, Dawn Chorus, etc?

problem:

My hearing falls off severely above 1kHz. Something like -50 dB at 7kHz

Any suggestions for a frequency downshifter - think bat detector?

Take care

John
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