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Attempt at receiving ELF

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Avalanche

Sun Sept 27 2009, 11:46AM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

Hi all,

A few months I came across this page

and was always interested in giving it a try.

Anyway, yesterday I built the receiver shown, with only a few small differences in that I used KA358 amplifiers and some 5-15v DC-DC converters to form the various rails. It seems to work, but I think the cutoff frequency is too low! Going by the maximum rate of rise on the scope, it seems to cut off around about 5Hz? For an 'antenna' I used 2x 1 foot copper tubes hammered into the ground 4 meters apart. They are connected to the receiver via a 20 meter length of RG58 coax.

Has anyone else had any luck in receiving anything at frequencies this low?

Here's some pics

The receiver - powered by an old laptop PSU

Typical signal on the scope - 1 second timebase

Signal followed by a period of silence...

... which can go on for a while

Not sure if these results even mean anything but that's what I'm getting

Proud Mary

Sun Sept 27 2009, 11:58AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

I tried to receive the Schumann Resonances, but there seems too much interference from a local power station to receive anything definite

Avalanche

Sun Sept 27 2009, 12:07PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

What was your setup? I think it all comes down to filtering, this receiver has absolutely no output at 50Hz with a 100m spool of wire connected across the input, but I can stand 2 meters away from the spool with a magnet and get about 10v p-p on the scope at 2hz by rotating the magnet.

I haven't got a clue what the other signals are that I'm getting

Proud Mary

Sun Sept 27 2009, 01:56PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

I used the two valve rig described on the Italian below 22kHz site - with just a few modifications - I had a grid leak resistor of suitable size - and displayed the output via the audio input of my PC as a spectrum. I'm not sure that it really went down to 5Hz, though it did when viewing the 5Hz from a sig gen.

As for the 'mystery signals' I wondered if they couldn't be connected with a local electric railway, or command signals sent down the 132kV lines from a local power station, and switching farm.

I get French electricity, which I believe has complex command signals embedded in it, (to change remotely meter rates and so on) but am not up to date on the details.

I wondered if you might get a better impression using a spectrum analyser.

I have found the following supplier of close tolerance high value silver mica capacitors very reliable over the past year:

Scott Fusare

Mon Sept 28 2009, 10:49AM

Registered Member #531 Joined: Sat Feb 17 2007, 10:51AM
Location: Burlington, Vermont
Posts: 125

A number of years back I was successful in detecting the Schumann resonances electrical field component. Personally I think E-field reception is the simpler and cheaper approach to the problem, but that's a matter of opinion.

As the article you posted resides on Renato's website you have already found the mother load of hobbyist VLF-ELF information. I highly recommend Renato's book also, great stuff.

Assuming you are chasing the Schumann peaks the challenge is the same no matter what technique you choose â€“ small signal of interest buried in, potentially, huge man made noise.

Are the Schumanns what youâ€™re after?

Scott

Proud Mary

Mon Sept 28 2009, 03:49PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Hi Scott, I agree about the E-field being the only practical proposition. Unless you are a total Schumann junkie, you could never justify the very high cost of trying to detect the magnetic component. I'm sure you've seen pics of giant solenoid ELF antennae that must have cost an arm and a leg in copper wire alone, let alone the effort involved only to bury it in a hole!

But I'm not sure this thread is about the Schumann's, but about anomalous ground signals, so we'd better leave it to Avalanche to pick up his thread in the right direction.

Scott Fusare

Mon Sept 28 2009, 05:11PM

Registered Member #531 Joined: Sat Feb 17 2007, 10:51AM
Location: Burlington, Vermont
Posts: 125

Hi Harry,

Yes, I have seen the pictures. My favorite is the giant air core version. Must have been hellishly sensitive to vibration.

Didn't mean to drag the thread off topic. I have a bad habit of reading ELF / ULF and thinking the Schumann peaks are the target. Ground currents are an area I have not explored experimentally.

I'll let Avalanche clarify before I babble on..

Scott

Avalanche

Mon Sept 28 2009, 05:14PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

sorry, yes - I'm was just having a go at picking up anomalous signals, similar to those shown on that page. I thought it might be interesting and fairly simple equipment wise. The original author reported having more success with the probes in the ground, so I thought I'd start there - receiving ground currents.

Just from looking at the scope, it doesn't look like I'm getting anything really. I'm going to try locating the receiver nearer to the ground probes first, then if I get any signal, the plan was to build an A to D converter which outputs results to RS232 for logging into a .WAV file, then I can view them on spectrum lab.

Proud Mary

Mon Sept 28 2009, 05:41PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

The problem is you don't know the origin of the signals in the original paper: they might be ground return signals from an electric railway, city lighting system - any number of possible human sources really.

I was a member of the ELFRAD group

but was kicked out for drawing attention to the radio signatures of tunnel boring machines apparently emanating from Johnston Atoll.

Scott Fusare

Mon Sept 28 2009, 06:12PM

Registered Member #531 Joined: Sat Feb 17 2007, 10:51AM
Location: Burlington, Vermont
Posts: 125

Avalanche -

Just a thought but given the "period of silence" you are seeing I would suspect something is saturating. You might have a peak at the signal just after the 1st amp and see what things look like. All the filtering in the world won't help if things have gone non-linear up front. If there truly is no signal, you might try moving your ground probes farther apart.

Harry -

I am curious about your Johnston Atoll story. Would you be interested in sharing it, perhaps in a PM if more appropriate?

Scott

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