Airport Spatial Usability in Measuring the Spherical Antenna Properties on Small Aircraft

The strict safety requirements of air transport for nonstandard placement of electronic onboard systems require an innovative approach to the experimental verification of the placement of these devices. Particular attention is required to the location of these electronic devices’ antenna systems on the fuselage. A prerequisite for determining the location of the antenna and verifying its radiation is a thorough knowledge of the radio communication transmission of onboard electronic systems in cooperation with terrestrial or satellite systems. From this point of view, this article focuses on an innovative method of verifying the spherical radiation characteristics of the antenna of an onboard rescue system emergency locator transmitter (ELT) to assess its communication link with the Cospas-Sarsat satellite system. The measurement is performed on a small sports two-seater aircraft with an antenna placed in an unusual place in the aircraft’s cabin, between the seats. It was impossible to use a suitable nonreflective attenuation chamber for the measurement, so we present a method and procedure for this type of measurement in the open space of an airport. The achieved results prove the plausibility and reproducibility of the measurement. Furthermore, combining several polar radiation characteristics makes it possible to obtain an idea, even if only a part, of the spatial (spherical) radiation characteristic. This article presents a simple method of measuring the characteristics of aircraft antennas when it is not possible to use a suitable professional nonreflective attenuation chamber for measurements for various reasons. This method can also be used on other larger means of transport or other objects that experience the same problem.

Penerima Sinyal Emergency Locator Transmitter dengan Metode Direct Receiver pada Frekuensi 121,5 MHz

To find out the location of an aircraft accident from an ELT signal beam of 121.5 MHz, search and rescue (SAR) officers or civil aviation authorities need an ELT signal receiver device that works at the same frequency, which is 121.5 MHz. The purpose of this research is to produce an ELT signal receiver with direct receiver method at a frequency of 121.5 MHz which is simpler, requires fewer RF devices, and is according to specifications for civil aviation. In this research, the design and realization of ELT signal receivers are carried out using the direct receiver method, including: a BPF and a RF amplifier as a direct receiver circuit, an AM demodulator, and an audio amplifier. Based on the results of measurements and tests that have been done, the direct receiver circuit can receive an ELT signal at a frequency of 121.5 MHz in the range of 121.330 to 121.617 MHz with -40.35 dB sensitivity, the AM demodulator can demodulate the audio signal at a frequency of 346.6 Hz, and the audio signal at a frequency of 337.6 Hz as a pointer to an ELT signal can be heard through the loudspeaker. The results of this study are ELT signal receivers with direct receiver method at a frequency of 121.5 MHz which are according to specifications for civil aviation.

OSILATOR 121,5 MHZ PADA ELT MENGGUNAKAN VCO MC1648

Pada saat terjadi kecelakaan pesawat terbang di suatu tempat, dapat diketahui posisi atau lokasinya dengan menggunakan suatu alat yang diletakkan pada badan pesawat terbang tersebut, yaitu emergency locator transmitter (ELT). Pada ELT terdapat komponen osilator sebagai pembangkit sinyal pada frekuensi 121,5 MHz, dengan spesifikasi militer yang tidak tersedia di pasar bebas. Pada penelitian ini dilakukan perancangan dan realisasi voltage controlled oscillator (VCO) menggunakan MC1648 sebagai osilator pada frekuensi 121,5 MHz, serta implementasinya pada pembangkit sinyal ELT. Hasil pengukuran menunjukkan VCO sebagai osilator dapat membangkitkan sinyal keluaran berupa gelombang sinusoida dengan tegangan antara 11,60 s.d. 41,5 mVpp dan rentang frekuensi 90,88 s.d. 126,75 MHz, dimana frekuensi = 121,5 MHz dapat dibangkitkan pada tegangan DC masukan = 4,25 VDC. Rangkaian VCO sebagai osilator 121,5 MHz hasil penelitian ini, dapat diimplementasikan pada pembangkit sinyal ELT hasil penelitian sebelumnya, sehingga dapat dibangkitkan sinyal ELT pada frekuensi 121,5 MHz, berupa gelombang AM dengan indeks modulasi = 24,05%.