1. Recepia semnalelor de frecvenfoarte joasGabriel Iana
2. Cuprins Originea semnalelor Tipuri de semnale provenite din
natur Aplicaii Comunicaii Navigaie Modele de antene
3. Pentru a recepiona semnalele de joasfrecven trebuie s
cunoatemsemnalele din natur Semnale electromagnetice provenite
dinmediul ambiant Semnale generate de factorul uman
4. Nature RadioIdeea de ascultare a unei emisii care nuprovine
de la un operator radio, un modem sau dede la orice dispozitiv,
uneori ne surprinde pentru cne asteptm s gsim un zgomot de la o
descrcareelectric sau ceva de genul acesta. Dar cnd vomgsi un ton,
sau un semnal de tip whistler i multealte suprapuse, precum un cor
de voci umane,suntem uimii pentru c nu le-a generat nimeni.Cnd
descoperim legturile dintre aceste emisii icmpul magnetic al
pmntului, a celor atmosfericeprecum furtunile sau reacii fizice
atomice care sepetrec cteva mii de kilometri de Pmnt,
rmnemstupefiai.
5. Originea SemnalelorCmpul magnetic terestru
6. Magnetosfera Este la 200km altitudine unde micarea
sarcinilorelectrice este controlat de cmpul magnetic alpmntului In
interiorul mangetosferei sunt zone mari de radiaiinumite Van Allens
Band
7. Descrcrile electrice atmosferice Crusta pmntului esteformat
din minerale iap srat (buneconductoare electrice) Potenialul n
partea desus a atmosferei estede peste 400000V Intre un nor si
pmntse poate ajunge la odiferen de potenialde 2-3milioane de
Voli
8. Cmpul biomagnetic
9. Tipuri de semnaleRezonana Shumann Sunt n jur de 2000furtuni
la un moment dat Se produc aproximativ 50descrcri electrice
pesecund Semnalele se reflectacam de la 100kmnalime Frecvena de baz
7.8Hzi armonice la (15.6,23.4, 31.2 Hz)
10. Fluierturi (The whistlers) Sunt semnale cu frecvene
cuprinse ntre 1kHz i 30Khzcu amplitudine maxim ntre 3kHz si 5kHz.
Sunt produse de fulgerele crora impulsul magnetictraverseaz
ionosfera si apare o dispersie de civa kHz
11. Fluierturi (The whistlers)
12. Fluierturi (The whistlers)
13. Activiti seismice Sunt observatoare seismice care
analizeazcmpul magnetic generat de ctre micrilescoarei terestre
pentru a le preveni Acestea sunt mprite n 2 benzi de frecven:
0.01Hz i 12Hz 30 i 150Hz
14. Activiti seismice
15. Clasificare benzi radioNume Band FrecvenELF Extremely Low
Frequency 3Hz - 30HzSLF Super Low Frequency 30Hz - 300HzULF Ultra
Low Frequency 300Hz - 3000HzVLF Very Low Frequency 3 - 30 kHzLF Low
Frequency 30 - 300 kHzMF Medium Frequency 300 - 3000kHz (0.3 - 3
MHz)HF High Frequency 3 - 30 MHzVHF Very High Frequency 30 - 300
MHzUHF Ultra High Frequency 300 - 3000 MHz (0.3 - 3GHz)SHF Super
High Frequency 3 - 30 GHzEHF Extremely High Frequency 30 - 300
GHz
16. Aplicaii ale semnalelor de joasfrecven n comunicaii
Comunicaia ntre sisteme care nu se afl lasuprafa (sub ap, n sol)
Sisteme de navigaie pentru submarine, vapoare,sisteme militare,
etc. Detecie materiale explozive din incinte ecranateSTATIONS, ITU
LICENCES AND SERVICES BELOW 22 kHz50 Hz - 7.04 kHz Range of
frequencies to be transmitted by Space Shuttle mission STS-45 in
mid March 1992.45 Hz Navy test frequency for submarine
communications from US sites 197016.6667 Hz Mains power frequency
for railways (Norway). Also referred asindustrial frequency.13 Hz
Second Schumann resonance10 Hz Emissions from MIR, INSPIRE Project7
Hz The first Schumann resonance for the earth ionosphere cavity.1
Hz Frequencies in this range may be related to earthquake &
seismic events.
17. STATIONS, ITU LICENCES AND SERVICESBELOW 22 kHz1280 Hz Test
done at Kaford, Norway in 1979/80. ERP was 29W.1200 Hz MIDAC a
system used by cavers to communicate with the surface. CW is
useddown to 1200 below ground.1025 Hz Bynary tones on electric
mains power, to change accounting rates in homecounters (e.g., used
in Switzerland).OOK modulation.983 Hz A ULF beacon available for
testing purposes in the USA.874 Hz A frequency mentioned in
BREAK-IN in reference to an underground cavingexpedition.470 Hz
Bynary tones on electric mains power, to change accounting rates in
homecounters, like 1025 Hz76 Hz SANGUINE or Project ELF. A US navy
submarine communications network.75 Hz Used during US tests in the
1970s. Replaced by 76Hz. See also 45Hz.70 Hz Submarine
communications60 Hz Mains power (N. America and other countries)50
Hz Mains power (Europe)
18. Sisteme de comunicaii la submarine Generarea de cod binar
76Hz pentru U.S. 82Hz pentru Russian system Putere radiat efectiv
mic 1-7W Se pot recepiona pe tot globul cu o anten T detip Marconi
cu o bucla de 2100 m2
19. Sisteme de comunicaii la submarine
20. Instalaie n bandaELF pentrusubmarine ntreMichigan
iWisconsin.Instalaiile sunt la238Km distan isemnalul radioeste
generat decurentul dintrecele dou staii.
21. Sisteme de comunicaii
22. Recepie n banda de 82HzA Zevs transmission recorded in
Italia by Renato Romero on the 8th of December 2000, at08:40
UTC
23. THE RUSSIAN VLF NAVAID SYSTEM,ALPHA, RSDN-20Segment
nr.stationFrequency kHz1 2 3 4 5 6F3p 14.881091
kHzNovosibirsk,Revda, SeydaF3 14.880952 kHz Krasnodar Khabarovsk
Novosibirsk Seyda RevdaF2 12.648809 kHz Revda Novosibirsk
Khabarovsk Krasnodar SeydaF4 12.090773 kHz RevdaF5 12.044270 kHz
SeydaF1 11.904761 kHz Novosibirsk Seyda Krasnodar Khabarovsk
RevdaNEW RSDN-20transmission sequenceby frequencyNOVOSIBIRSK
55:45:22.0 N 84:26:52.4 EKRASNODAR 45:24:17.9 N 38:09:29.0
EKHABAROVSK 50:04:23.9 N 136:36:24.1 EREVDA 68:02:07.8 N 34:41:00.0
ESEYDA 39:28:16.0 N 62:43:07.3 E
24. The Russian VLF time-signal stations,Beta
25. Antene de recepie
26. Antena bucl (magnetic)
27. Antene bobinate (magnetice)Number of turns: 96000Wire
diameter: 0,16 mm (AWG34)Winding length: 80 cmThick winding: 0,178
cmLength of wire: 13,44 kmWeight of copper wire approximately: 2,5
kgSingle turn area: 0,001225 square meters (3,5x 3,5 cm)1 pT field
gives a voltage output of 0,354 mV(+/- 3 dB)1 mV voltage output
corresponds to a field of2,82 pT (+/- 3 dB)
28. Preamplificator anten magnetic
29. Concluzii Semnalele de joas frecven reprezint o bazde
studiu att pentru cele recepionate din naturdar i cele generate de
om Recepia acestora n conjucie cu software-ulradio pot fi analizate
i demodulate pn lafrecvena de 24kHz (frecvena maxim a plcii audio
de calculator) O provocare n domeniul cercetri cost nrealizarea
unei posibile legturi ntre semnalelede joas frecven i percepia
celui de-al 6-leasim la animale.
30. Bine ai venit n aceast lumeexotic i distrai-v!