ABSTRAKSI: LORAN-C (Long Range Navigation-C) merupakan teknik penentuan posisi yang beroperasi pada frekuensi rendah 100 KHz. Loran-C terdiri atas beberapa stasiun transmitter yang terpisah beberapa ratus mile dan membentuk chain. Dalam satu chain, satu stasiun berperan sebagai master dan yang lain sebagai secondary. Setiap chain minimal terdiri atas satu master dan dua secondary untuk menghasilkan dua kurva line of position (LOP). Master dan secondary mengirimkan pulsa pada interval waktu yang tepat ke suatu titik observasi (target/ user). Receiver Loran-C mengukur time difference (TD) antara saat pengamat (user/target) menerima pulsa dari master dan saat menerima pulsa dari masing-masing secondary. Ketika perbedaan waktu tersebut dikonversi ke jarak, lokus dari titik-titiknya mempunyai TD yang sama antara master dan masing-masing secondary, kemudian membentuk kurva hiperbolik LOP. Interseksi dua atau lebih LOP hiperbolik, menghasilkan posisi.
Dalam Tugas Akhir ini dibahas mengenai perencanaan sistem Loran-C di Indonesia, meliputi penentuan spesifikasi transmitter dan receiver Loran-C , penentuan lokasi transmitter berdasarkan perhitungan kuat sinyal Loran-C yang dipancarkan dan kuat noise yang berpropagasi melalui gelombang tanah (groundwave) dan perhitungan GRI (Group Repetition Interval). Serta mensimulasikan penentuan posisi menggunakan software matlab 6.5. Kemudian melakukan analisis hasil perencanaan dan perhitungan akurasi sistem Loran-C.
Hasil perencanaan menunjukkan bahwa jarak jangkauan transmitter ke receiver sangat dipengaruhi oleh daya pancar, permukaan bumi yang dilalui dengan konduktivitas dan permitivitas yang berbeda-bada serta noise. Sedangkan GRI harus cukup besar agar dapat memastikan bahwa pulsa masing-masing transmitter sampai ke user dengan sempurna sebelum cycle GRI dimulai kembali. Namun harus cukup kecil agar delay waktu tidak terlalu besar. Simulasi memberikan informasi akurasi sistem Loran-C.Kata Kunci : Loran-C, ground wave, Hiperbolik line of position, Time difference.ABSTRACT: LORAN-C (Long Range Navigation-C) is position determination method, operate in 100 KHz Low Frequency. Loran-C system consists of transmitting station, which are placed several hundred miles apart and organized into chains. Within a Loran-C chain, one station is designated as the master station and the others as secondary stations. Every Loran chain contains at least one master station and two secondary stations in order to provide two lines of position. The master and secondary stations transmit radio pulses at precise time intervals. A Loran receiver measures the Time Difference (TD) between when the observer (target / user) receives the master signal and when it receives each of the secondary signals. When this elapsed time converted to distance, the locus of points having the same TD between the master and each secondary forms the hyperbolic LOP. The intersection of two or more of these LOPs produces a fix of users position.
This final project explain about Loran-C system planning in Indonesia, include determination of transmitter and receiver Loran-C specification, determination of transmitting stations location based on field strength radiation calculation and noise prediction that is propagate pass through ground plan and group repetition interval (GRI) calculation. And, it simulate position determination uses matlab 6.5 software. Then, both results of planning and simulation are analyzed.
The result of planning indicates that length of range from transmitter to receiver is affected by power radiation, ground plan which is has difference conductivity and permittivity each other and the noise. Further, GRI must great enough to certain each transmitter pulses perfectly achieve to the user before GRI cycle turn again. But must small enough so the delay not too long. Simulation shows information of Loran-C system accuracy.Keyword: Loran-C, groundwave, hyperbolic line of position, time diferrence.