Schumanns

Detection and recording of Schumann resonances proved to be more difficult than

first expected. Initially I wanted to use my large ground loop , but never managed

to see even the slightest trace of the Schumanns. Renato (IK1QFK) showed me

that it was almost impossible to receive them with horizontal loops. Vertical polari-

zation was required; this needed a bit of a re-think.....

That's why I built the 200 turn Octoloop next, which made Schumann resonance

detection possible. But due to loop microphonics, reasonable interference free

reception is only possible when there is not much wind.

Finally the big induction coil was built; this enables reception unaffected by weather,

but (there seems to be always a "but") daytime operation is still riddled with some

forms of interference. I call this collectively " human activity" . Because during the

early evening hours the various low frequency spectrum spikes (~2......25Hz)

slowly disappear and during most of the night clean spectra are recorded.

Throughout the experimentations with Schumann resonance reception it was always obvious that

the weather had a profound influence on the quality and appearance of the recordings, at least in

my location here. This may well be tied in with the presence of H.V. power lines within a km of the

sensing coil(s). So far I never had the opportunity to escape into the remote Australian interior with

my induction coil and PC, and make a few days worth of recordings , but I'm tempted !!

To illustrate the problems, look at the following spectra :

Weather dry, but strong winds Spectrum 9 , note the strong spectral lines around 17 & 22Hz,

also a weaker line ~ 5Hz. Reasons for the presence of those lines are not clear (as yet).

Same again, but comparison between ind.coil and underground loop Spectrum 10

As before, the left section shows the 5,17 & 22Hz lines (induction coil), the right side

(40 turn underground loop) shows different lines altogether, preamp 12Hz LPF.

Same again, but comparison between ind. coil N-S, and then E-W alignment . Spectrum 11

This is more surprising, at least 50% of dominant lines change when orientation

of the induction coil axis was changed through 90 deg.

This one showing how the Schumanns get affected by sudden rain Spectrum 12

Same again, two rain showers Spectrum 13

And the extreme, continuos strong winds and rain Spectrum 14

And here a little experiment:

Extracted the 7.8Hz component with a low Q bandpass filter (Q=2) and modulated the VCO port of

a function generator chip (XR2206), carrier frequency ~ 615Hz. This makes the otherwise sub -

audible 7.8Hz Schumann resonance audible by "warbling" the 615Hz carrier. Unfortunately there

are also occasionally high level transients (noise spikes), and these cause a sudden ,large frequen-

cy displacement with some ringing. The .wav file is ~ 340kB long, the last 5 seconds of the 30 secs.

recording have (for comparison) the signal modulation switched off. Schumann.wave

Later in the year a different approach was tried. Scott Fusare has shown that Schumann resonances

can be readily recorded with a simple E-field antenna, like a 6ft vertical rod. Initially I found this hard

to believe , considering the detectors the professional researchers were using. But there was no point

theorising how this can possibly work. The simple solution was to construct a similar device as Scott

had designed, and also using a similar antenna. The best link to his work that I could find was at

Eric Vogel's excellent site ,( this link comes via Peter Schmalkoke's site ) > E-field antenna

Many simultaneous E-field and H-field recordings were made over a time span of a few months ,and

the results were surprising. Quite often the vertical antenna would perform better than the induction

coil, but only at the first two resonances. Since both detectors are using the same post-amplifier

and filtering circuits, the frequency response should be the same for each. At other times the induct-

ion coil was better. In any case, the induction coil was usable at all times, whilst the vertical antenna

only usable when (weather-) conditions are good. Considerable care was taken to prevent creepage

resistance, as well as the antenna was guyed with three nylon strings in order to minimize movement

caused by wind. Despite all this, there were sometimes long spans of time, in the order of hours ,

when no or very little Schumann resonance signals was detected from the vertical, whilst normal

signal levels can be observed with the induction coil. Measurements made during such occasions

indicated no identifiable malfunction in the FET front-end buffer , the range of measured d.c. volts

at critical circuit nodes being similar to when receiption was good.

It was never really resolved if this is just a local effect, or widespread, even global. But I suspect

the reason for this maybe the fact that with such a minimal pick-up device like a 6ft rod, there is no

amount of signal to spare. Everything has got to be just right, no margin for environmental effects.

I have encountered a similar thing with amateur radio astronomy. With very small antennas , like

3...6 metre dishes, one can on occasions record surprisingly weak radio sources, but only the large

instruments will give reliable and repeatable detections.

I'm planning to build a larger vertical antenna, which hopefully will give good performance at

all times. Renato Romero is using a large top loaded vertical system ,which as I understand ,

allows reliable Schumann recording. > Marconi-Tee

Here is a spectrogram of a E - and H - field simultaneous recording > Vert.+ ind.coil

July 2002 - Built and tested a vertical ~ 4m tall with a 0.6m dia. round aluminium plate on top

to add capacitance. Total capacitance ~ 86pF. Still using a derivative of Scott Fusare's pre-amp,

but input resistance reduced to 300MOhms. This value was determined experimentally.

This device now gives consistently better results than the induction coil !! It also has the added

bonus of being less sensitive to power mains interferences than the induction coil.

Pictures : E-field antenna antenna capacitive top hat insulator close-ups A B