AMRAD-OSCAR 27 as well as EYESAT-1 or simply AO-27 is a satellite similar to UO-14. Of everything on board, it is the most interesting for radio amateurs FM crossband converter. Dvanásťkilogramový satellite na obežnú dráhu s inklináciou 98,5° a dobou obletu 101 minút vyniesla Ariane 4, ktorá odštartovala 26.septembra 1993 01.47 UTC z Korou vo Francúzkej Guayane.
The shuttle carried a German laser reflector, Healthsat-II, PoSAT-1, and amateur satellites KITSAT-OSCAR-25 (KO-25) and Italy-OSCAR-26 (IO-26).
EYESAT-1 is a MICROSAT-class satellite built by Interferometrics Inc. of Chantilly, Virginia to monitor the movement of vehicles in industry. On board is the AO-27 converter, which was constructed by the members AMRAD P.O. Drawer 6148 McLean, Virginia, USA, 22106-6148, a technically oriented, non-profit, amateur radio organization.
The AO-27 has a crystal controlled FM receiver on 145.850 MHz and also crystal controlled FM transmitter at approximately 436.795 MHz with output power: via 1W (rarely used); 0.5W or under 0.1W (only from the exciter). The uplink antenna is a linearly polarized whip on the front of the satellite, the downlink antenna is 1/4 on the side of the satellite. The rotation and turning of the satellite thus causes a relatively significant effect QSB.
So that the satellite can work for many years with a limited amount of energy it is switched on only for part of the trip. The converter is turned on when its imaginary footprint on Earth will exceed 37°N with solar panel lighting, sometimes also during weekend and evening flights. After five years of operation, this philosophy proved to be correct, as the on-board battery showed only minimal wear.
Like any FM converter, the AO-27 can convert at a moment's notice only a single signal. In order for multiple stations to be able to communicate during the flyby, the cooperation and consideration of the individual operators is necessary - above all, listen before we press PTT.
The AO-27 receiver is very sensitive, a good signal can be achieved with 25W into an average gain omnidirectional antenna. It is not necessary to correct the Doppler frequency shift on the uplink frequency. With a sensitive UHF FM receiver, preamplifier and omnidirectional antenna, the AO-27 signal can be received with leakage, with a smaller directional antenna, the signal is already solid. The Doppler frequency shift at 436.795 MHz is already +/- 9 kHz and must be corrected.
The signal on the downlink is 4-7 dB weaker than the UO-14. With a power of 0.5W and a distance of 800-3200 km between the operator and the satellite, it is clear that with You can no longer succeed with a "rubber" antenna. At best, the signal will be very weak and unstable. When using 1/2 antenna, the recommended sensitivity of the receiver is at least 0.18uV 12 dB SINAD, if we want to achieve at least an average signal at an elevation of 10° or more. Improvement can be achieved by using a reflector and rotating the antenna.
For the first attempts, it is advisable to choose weekend tours with a higher elevation. We open the squelch and try to capture signals from the converter around the downlink frequency. UFB is tuning after 1 kHz, in emergency at least after 5 kHz. We have to 100% understand the station we want to call, if we have a suitable device for 2 m, we will give our call once or twice. And we are waiting for an answer….
The latest information is available from Weekly Satellite Report, the official AO-27 website http://www.ao27.org/ a AMRAD In Space — AO-27 .