EXPLORING VLF AND ELF FREQUENCIES By John Bailey

EXPLORING VLF AND ELF FREQUENCIES By John Bailey M 0 MTW

EXPLORING VLF AND ELF FREQUENCIES 1. What frequencies VLF (Very Low Frequencies) 2. What can be heard? . 3. Professional VLF Radio Stations 4. Local Interference 5. Strange behaviour of radio at VLF 6. The receivers and Antennas 7. Analysing the signals – software ELF (Extra Low Frequencies) – as with VLF 8. Next Projects 9. Online sources

The frequencies BAND Frequency ELF – Extremely Low Frequency SLF – Super Low Frequency ULF – Ultra Low Frequency VLF – Very Low Frequency LF – Low Frequency MF – Medium Frequency 0. 1 – 3 Hz 3 – 30 Hz 30 – 300 Hz 300 – 3 k. Hz – 30 k. Hz – 300 k. Hz

Starting with VLF • 300 Hz to 3 KHz (Commonly given as 300 Hz to 30 KHz)

VLF theory • As VLF wavelengths are very long they can diffract around large obstacles. • They can propagate as ground waves around the curvature of the Earth. • The Ionoshpere ‘D’ layer at 60 k. M reflects the VLF wave between this and Earth ground a duct a few VLF wavelenths high is formed. • The duct acts a waveguide waves following a zigzag path around the world. • VLF waves have very low attenuation 2 -3 d. B per 1000 k. M. • Attenuation is low because VLF waves are reflected at such a low level unlike shortwave signals being reflected at higher levels and more affected by ionisation. • Propagation distances of 5000 to 20000 k. M can be achieved and are more stable than higher frequencies. • On the down side VLF signals are subject to more atmospheric noise.

Natural VLF radio signals • Static discharges – lightning • “spherics” atmospherics radiated by lightening. • Tweeks – sounds like twittering and is a deformation of the static propagating. • Insects – produced by current flowing between clouds and ground – frequency can vary with time. • Whistlers - reducing infrequency over periods from half to several seconds. Several types of whistler can be identified. • Auroral chorus – can sound like musical whistles, varying in both tone and frequency. • Flying Saucers – connected to aurora phenomenon.

SOLAR FLARES • Solar flares can be detected at VLF frequencies. • This is often achieved by continuously monitoring signal levels of military transmissions. • A Solar Flare is caused by the sudden collapse of the very highly strained magneticfield in the region of a Sun-spot.

SOLAR WIND • The solar wind and cosmic rays can be monitored by VLF equipment. • Measurements taken by various space probes. • The solar wind deforms the earth’s magnetosphere.

Man made VLF signals • Submarines • Radio Navigation • Time Radio Stations

THE VARBERG RADIO STATI 0 N • The Varberg Radio Station at Grimeton is a VLF transmission facility at Grimeton near to Varberg, in Halland, Sweden. • It has the only working Alexanderson alternator rotating armature radio transmitter in the world. • 200 k. W Output

THE VARBERG RADIO STATI 0 N • The transmitter was built in 1922 to 1924 to operate at 17. 2 k. Hz. • The antenna is a 1. 9 km (1. 2 mile) flattop wire aerial consisting of eight horizontal wires suspended on six 127 -metre high freestanding steel pylons in a line. • The Grimeton VLF transmitter location is also used for shortwave transmissions, FM and TV broadcasting. • Upto the 1950 s, the Grimeton VLF transmitter was used for transatlantic radio telegraphy to Radio Central in Long Island, New York, USA. From the 1960 s until 1996 it transmitted orders to submarines in the Swedish Navy.

GRIMETON RECEPTION REPORTS • Grimeton transmits twice a year on 17. 2 k. Hz CW, at the end June / beg. July (Anderson Day)and Christmas Eve (extra transmission 16 th August 2016) • Above is the reception report from 3 rd July 2016

SAQrx SOFTWARE • SAQrx is a soundcard based receiver covering 0 -22 k. Hz. • Was written to allow listening to the Grimeton transmissions. • Is available to download free from SM 6 LMK https: //sites. google. com/site/sm 6 lkm/saqrx/

MILITARY STATIONS • VLF Transmitter - Yosami , Japan -In April 1929, the Yosami Station established the first wireless communications between Japan and Europe with a long wave operating at 17. 442 k. Hz. An inductor-type high-frequency alternator provided output power at 500 k. W. • The antenna system used eight towers, each 250 m high. The facilities were used for communicating with submarines by the Imperial Japanese Navy from 1941 to 1945 and by the United States Navy from 1950 to 1993.

Strange behaviours of radio waves at VLF frequencies. Penetrate water ~ 40 meters in saltwater. Very large wavelengths mean signals are not blocked by mountain ranges. Suffer little of fading experienced at other frequencies. Subject to high atmospheric noise (sferics) like whistlers caused by lightening.

DIFFERENCE BETWEEN ELECTRIC AND MAGNETIC FIELD • To listen to VLF signals you need to choose between electric field and magnetic field receivers. • The differences are small as both carry the same information. • Example a VHF FM signal received with a whip aerial receives the electrical component whilst long waves received using a ferrite rod aerial receive the magnetic component. • Generally the antenna to receive the electrical component is most often used as its easier to construct.

Interference & noise. • Mains Hum – harmonics extend to over 10 KHz • Signals from high voltage power lines. • Electric motors • TV-Line timebase. • Radio navigation • Military RTTY

50 HZ MAINS HARMONICS • A problem at lower VLF frequencies.

Other disturbances • Local obstructions • Trees shielding signal. • Insects – weak electrostatic field variations – sensitive electric field receivers with whip antennas. • Static discharges from clothes • Wristwatches - when using a magnetic field receiver the weak VLF magnetic fields of wristwatches are detectable. • Cars –Ignition noise is detectable from 200 meters distance.

OPERATING LOCATIONS • • Remote Away from sources of interference – mains hum – power lines No obstructions Away from industrial areas

ANTENNAS • Trideco" antenna tower array at the US Navy's Radio Station in Cutler, Maine, USA. • The central mast is the radiating element, with a star-shaped horizontal wire array. • About 1. 2 miles in diameter, it communicates to submerged submarines on 24 k. Hz at a power of 1. 8 megawatts, the most powerful radio station in the world

ANTENNAS • US Navy Communications Station , Panama. • Established in 1908 in use upto 1960 s? • A cryptographic centre and a fleet broadcast centre

Audio Clips • What do they sound like : Whistler Dawn Chorus Pure whistler 2 hop whistler http: //www. astrosurf. com/luxorion/audiofiles. htm

Audio Clips 2 Auroral chorus Periodic emissions Magnetic Storms Flying Saucers Distant thunderstorms

Commercially available equipment WR-3 ELF/VLF RECEIVER http: //www. auroralchorus. com/wr 3 gx 2. htm NASA INSPIRE VLF-3 Receiver http: //theinspireproject. org/

HOMEBREW EQUIPMENT Lots of handheld equipment because its portable and can be operated in quieter more remote locations.

MY EQUIPMENT VLF BBB 4 ELECTRIC FIELD RECEIVER (STEVE MCGREEEVY) • • High impedance input. Short whip antenna Portable Simple circuit with good performance.

BBB 4 CIRCUIT I added a 50 Hz Filter to reduce mains hum

THE FLOATING RECEIVER

THE FLOATING RECEIVER HOW IT WORKS • The floating receiver is a variant to the electric field receiver. • Instead of taking the signal between the antenna connection and ground it’s taken between two symmetrical antenna terminals. • By avoiding the ground connection the receiver has two advantages : - Illininates noise from the ground connection, collects signal present in the air only. - Avoids noises from the PC through connecting cables.

THE FLOATING RECEIVER • Constructed on veroboard. • Resistive bridge 2 x 100 M resistors using 10 x 10 M resistors in series.

MY EQUIPMENT *Antenna 5” drain pipe *2 sheets heavy duty aluminium *Each sheet separated by 100 mm *Receiver located inside drain pipe to weather proof. *Connected by 10 metres of screened cable to pc. Antenna is not resonant and can be small.

Analysing the signals – software FFT (fast Fourier transform software)analysis of the received signals. * SPECTRAN – I 2 PHD / IK 2 CZL * SPECTROGRAM – Richard Horne * SDR#

SPECTRAN • Has an effective mains hum filter included.

GRAPHICAL REPRESENTATION OF SIGNALS • WHISTLER

• Spectum Lab • TWEEKS

ELF frequencies (the sub-audio band) Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths from 10, 000 to 100, 000 kilometers. In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 k. Hz.

About ELF frequencies Difficulties of ELF communication • ELF waves propagate slightly slower than the speed of light in a vacuum. • Wavelengths are extremely long comparable to the earths diameter. • Two US maintained sites, one in Chequamegon-Nicolet National Forest, Wisconsin and another in the Escanaba River State Forest, Michigan • -these use long ground dipoles with multiple strands ranging from 22. 5 to 45 Kilometers.

ELF FREQUENCIES ELF effects on human nervous system • A study in 1999 showed that the threshold for direct perception of exposure to ELF RF by human volunteer subjects started at around 2 to 5 k. V/m at 60 Hz, with 10% of volunteers detecting the ELF exposure at this level. • ELF at human perceivable k. V/m levels was said to create an annoying tingling sensation in the areas of the body in contact with clothing, particularly the arms, due to the induction of a surface charge by the ELF.

ELF ANTENNA • A half wave dipole for 80 Hz would measure 1162 miles. • Elf transmissions through the earth need very high transmitted power in the mega watt range.

Uses of the ELF Band • Submarine communications. • Railways – Norwegian rail system supplies 16 k. V AC at 16. 66 Hz to its engines. • HAARP – Auroral Research based in Alaska. • Mains networks.

ELF FREQUENCIES

Natural Signals in the ELF band • Schumann resonances discovered in 1952 by W O Schumann. Formed by excited statics within the cavity between the earth and the ionosphere. • Long distance sferics. • Whistlers and Hiss – 200 Hz down to 20 Hz taking upto a minute to pass. • Magnetic Pulsations – formed in the magnetosphere.

Graphical display • Shumann Resonances

Simple ELF Receiver

ELF Antennas

RESEARCH GROUPS • Stanford VLF Group - The Stanford ELF/VLF group is exploring an alternative method of ELF/VLF wave generation, which utilizes the same currents that make the northern lights, to turn the upper atmosphere into a big radiating antenna. • The VLF ELF Radio Research Institute - it carries out research into VLF and ELF radio waves, particularly naturally generated waves in the Earth's atmosphere, magnetosphere and ionosphere, such as whistlers and chorus. • NASA – solar storms and space weather reports. • The High Frequency Active Auroral Research Program (HAARP)

Using a PC soundcard BASIC PRINCIPLE The pc soundcard is used to convert the vlf signal into an audible signal. frequency is converted down to an audio frequency of 650 hz. Just connect some meters of wire as an antenna to the mic input of the soundcard and try to listen to a local signal source. Add a simple lc network parallel to the input as vlf preselector this will protect your soundcard if you connect a longer piece of wire An active antenna can also be used.

Online VLF receivers https: //www. ab 9 il. net/vlf 1. html LOCATION STREAM TYPE DELFT, NETHERLANDS **Software Defined Radio** Tuneable SDR CAPE CORAL, FL, USA MONO SEBRING, FL, USA MONO MARLTON, NJ, USA MONO HAWLEY, TX, USA MONO BIELEFELD, GERMANY MONO CUMIANA, ITALY MONO SHEFFIELD, UK MONO TODMORDEN, UK MONO BIELEFIELD + CUMIANA STEREO MARLTON + SEBRING STEREO TODMORDEN + BIELEFIELD STEREO TODMORDEN + MARLTON STEREO

NASA Online VLF receiver http: //www. spaceweather. com/glossary/inspire. html

NEXT PROJECT RCM 2 Easy Loop Antenna IK 1 QFK • Uses single Op amplifier • 75 cm 40 turn Loop Antenna

NEXT PROJECT/S • ELF Receiver • SID Receiver -Sudden Ionospheric Disturbance Receiver – detects solar flares and gamma ray bursts. • Fluxgate Magnetometer – measures the intensity and orientation of magnetic lines of flux. • WSPR 137. 5 KHz 2200 M Beacon transmitter.

Further reading/sources Books: RSGB – RADIO NATURE – By Renat 0 Romero, IK 1 QFK ISBN: 9781 -9050 -8637 -5

THE END Thankyou for listening