Dziwani komwe mungapite ku eyapoti pogwiritsa ntchito RTL-SDR ndi GNU Radio

Pa Habr!

Pakalipano, palibe njira zambiri zoyankhulirana zomwe, kumbali imodzi, zimakhala ndi chidwi komanso zosangalatsa, kumbali ina, kufotokoza kwawo sikutenga masamba 500 mumtundu wa PDF. Chizindikiro chimodzi chotere chomwe ndi chosavuta kuchizindikira ndi chizindikiro cha VHF Omni-directional Radio Beacon (VOR) chomwe chimagwiritsidwa ntchito poyendetsa ndege.

VOR Beacon (c) wikimedia.org

Choyamba, funso kwa owerenga: momwe mungapangire chizindikiro kuti chiwongolerocho chidziwike pogwiritsa ntchito antenna yolandira omnidirectional? Yankho lili pansi pa odulidwa.

Mfundo zambiri

dongosolo Mafupipafupi Omni-directional Range (VOR) yakhala ikugwiritsidwa ntchito poyendetsa ndege kuyambira zaka za m'ma 50 zazaka zapitazi, ndipo imakhala ndi ma beacons amtundu waufupi (100-200 km), omwe amagwira ntchito mu VHF pafupipafupi 108-117 MHz. Tsopano, mu nthawi ya gigahertz, dzina lokwera kwambiri pafupipafupi molingana ndi ma frequency oterowo limamveka ngati loseketsa ndipo palokha limalankhula za zaka muyezo uwu, koma mwa njira, ma beacons amagwirabe ntchito NDB, ikugwira ntchito mumayendedwe apakati pa 400-900 kHz.

Kuyika mlongoti wolunjika mundege ndikovuta mwadongosolo, chifukwa chake vuto lidawuka la momwe mungasinthire zambiri za momwe amalowera ku beacon mu siginecha yokha. Mfundo ya ntchito "pa zala" ikhoza kufotokozedwa motere. Tiyerekeze kuti tili ndi nyali wamba yomwe imatumiza kuwala kocheperako kobiriwira, komwe nyali yake imazungulira nthawi imodzi pamphindi. Mwachiwonekere, kamodzi pa miniti tidzawona kuwala kwa kuwala, koma kung'anima kumodzi koteroko sikukhala ndi chidziwitso chochuluka. Tiyeni tiwonjezere yachiwiri ku nyaliyo osalunjika nyali yofiira yomwe imawala panthawi yomwe kuwala kwa nyaliyo "kudutsa" njira yopita kumpoto. Chifukwa Nthawi ya kuwala ndi kugwirizanitsa kwa beacon amadziwika; powerengera kuchedwa pakati pa kuwala kofiira ndi kobiriwira, mukhoza kupeza azimuth kumpoto. Ndi zophweka. Zimatsalira kuchita zomwezo, koma kugwiritsa ntchito wailesi. Izi zidathetsedwa posintha magawo. Zizindikiro ziwiri zimagwiritsidwa ntchito pofalitsa: gawo loyamba ndi lokhazikika (lofotokozera), gawo lachiwiri (losinthika) limasintha m'njira yovuta kutengera momwe ma radiation amayendera - mbali iliyonse imakhala ndi kusintha kwake. Choncho, wolandira aliyense adzalandira chizindikiro ndi kusintha kwake "kwake" gawo, molingana ndi azimuth kwa beacon. Ukadaulo wa "spatial modulation" umachitika pogwiritsa ntchito mlongoti wapadera (Alford Loop, onani KDPV) ndikusintha kwapadera, kopusitsa. Zomwe zilidi mutu wa nkhaniyi.

Tiyerekeze kuti tili ndi ma beacon wamba, omwe akugwira ntchito kuyambira zaka za m'ma 50s, ndikutumiza ma siginali mumayendedwe wamba a AM mu Morse code. N’kutheka kuti nthawi ina, woyendetsa sitimayo ankamvetsera matelefoni a m’makutuwo n’kumalemba mayendedwe ndi kampasi pamapu. Tikufuna kuwonjezera ntchito zatsopano ku chizindikirocho, koma m'njira yakuti "tisaswe" kugwirizana ndi zakale. Mutuwu ndi wodziwika bwino, palibe chatsopano ... Zinachitidwa motere - toni ya 30 Hz yotsika kwambiri inawonjezeredwa ku chizindikiro cha AM, ikuchita ntchito ya chizindikiro cha gawo lachidziwitso, ndi chigawo chapamwamba, cholembedwa ndi ma frequency. kusinthasintha pafupipafupi kwa 9.96 KHz, kutumiza chizindikiro chosinthika. Posankha zizindikiro ziwiri ndikufanizira magawo, timapeza mbali yomwe tikufunikira kuchokera ku 0 mpaka 360 madigiri, yomwe ndi azimuth yomwe tikufuna. Panthawi imodzimodziyo, zonsezi sizidzasokoneza kumvetsera kwa beacon "mwachizolowezi" ndipo zimakhala zogwirizana ndi olandira AM akale.

Tiyeni tichoke ku chiphunzitso kuti tichite. Tiyeni tiyambitse cholandila cha SDR, sankhani AM modulation ndi 12 KHz bandwidth. VOR ma beacon frequency atha kupezeka mosavuta pa intaneti. Pa sipekitiramu, chizindikirocho chikuwoneka motere:

Pankhaniyi, chizindikiro cha beacon imafalitsidwa pafupipafupi 113.950 MHz. Pakatikati mukhoza kuona mosavuta kuzindikira matalikidwe modulation mzere ndi Morse code zizindikiro (.- - ... kutanthauza AMS, Amsterdam, Schiphol Airport). Pafupi ndi mtunda wa 9.6 KHz kuchokera kwa chonyamulira, nsonga ziwiri zikuwonekera, kutumiza chizindikiro chachiwiri.

Tiyeni tijambule chikwangwani mu WAV (osati MP3 - kuponderezana kotayika "kupha" mawonekedwe onse a siginecha) ndikutsegula mu GNU Radio.

Decoding

mwatsatane 1. Tiyeni titsegule fayiloyo ndi chizindikiro chojambulidwa ndikugwiritsa ntchito fyuluta yotsika kuti tipeze chizindikiro choyamba. GNU Radio graph ikuwonetsedwa pachithunzichi.

Zotsatira: chizindikiro chotsika pafupipafupi pa 30 Hz.

mwatsatane 2: zindikirani chizindikiro cha gawo losinthika. Monga tafotokozera pamwambapa, imapezeka pafupipafupi 9.96 KHz, tifunika kuyisuntha mpaka zero frequency ndikuyidyetsa ku demodulator ya FM.

GNU Radio graph:

Ndi zimenezotu, vuto lathetsedwa. Tikuwona zizindikiro ziwiri, kusiyana kwa gawo komwe kumawonetsa ngodya kuchokera kwa wolandila kupita ku beacon ya VOR:

Chizindikirocho chimakhala chaphokoso, ndipo kusefa kwina kungafunike kuti pamapeto pake muwerenge kusiyana kwa gawolo, koma ndikukhulupirira kuti mfundoyo ndi yomveka. Kwa iwo omwe ayiwala momwe kusiyana kwa gawo kumatsimikiziridwa, chithunzi kuchokera aviation.stackexchange.com:

Mwamwayi, simuyenera kuchita zonsezi pamanja: zilipo kale ntchito yomaliza mu Python, ndikulemba ma siginecha a VOR kuchokera kumafayilo a WAV. Kunena zoona, kuphunzira kwake kunandilimbikitsa kuphunzira nkhaniyi.

Omwe ali ndi chidwi atha kuyendetsa pulogalamuyi mu kontrakitala ndikupeza mbali yomaliza kuchokera pafayilo yojambulidwa kale:

Mafani oyendetsa ndege amatha kupanga cholandila chawo chonyamula pogwiritsa ntchito RTL-SDR ndi Raspberry Pi. Mwa njira, pa ndege "yeniyeni" chizindikirochi chikuwoneka motere:

Chithunzi © www.aopa.org

Pomaliza

Zizindikiro zotere "kuchokera m'zaka zapitazi" ndizosangalatsa kwambiri kusanthula. Choyamba, iwo ndi osavuta, DRM yamakono kapena, makamaka, GSM, sikuthekanso kutanthauzira "pa zala zanu". Iwo ali otseguka kuti avomereze ndipo alibe makiyi kapena cryptography. Kachiwiri, mwina mtsogolomo adzakhala mbiri yakale ndikusinthidwa ndi satellite navigation ndi makina amakono a digito. Chachitatu, kuphunzira miyezo yotereyi kumakupatsani mwayi wophunzirira tsatanetsatane waukadaulo komanso mbiri yakale momwe mavuto adathetsedwera pogwiritsa ntchito madera ena ndi maziko azaka zapitazi. Chifukwa chake eni olandila amatha kulangizidwa kuti alandire zizindikiro zotere akadali akugwira ntchito.

Monga mwachizolowezi, mayesero osangalala aliyense.

Source: www.habr.com