AO-27 Demo

AO-27 transmits with a power output of 0.5 W into a quarter-wavelength whip antenna. Satellites are approximately 500 miles (800 km) distant when directly overhead and over 2,000 miles (3,200 km) distant when near the horizon. For use on AO-27 with a half-wavelength whip, your receiver sensitivity at 436 MHz should be at least 0.18 uV for 12 dB SINAD, which corresponds to the approximate signal strength of AO-27 at 10 degrees elevation when your whip antenna is correctly positioned for the polarization of the incoming signal. At the horizon, AO-27’s signal strength, under similar conditions, is approximately 0.13 uV. Most modern, high-quality amateur radio transceivers will meet these specifications if designed to operate at this frequency (i.e., without modifications). Most scanners, and most radios which have had to be modified to cover 436 MHz, will not.
AO-27 transmits FM on about 436.795 MHz, plus/minus Doppler shift of up to 10 kHz on either side. Their uplink frequency is 145.850 MHz, plus/minus Doppler corrections of up to approximately 3.4 kHz.
by Ray Soifer, W2RS

Continue reading