The Dream Project | Dream / Communications

Typically 70cm band is used.
Minimal power is needed, because of the high altitude and unobstructed line of sight. UKHAS uses 10mW.
The radio that UKHAS uses doesn't match the 70cm ARRL band plan. According to TMARC, we should use between 445.9250MHz and 446.0750MHz, as that's dedicated to simplex use.
The local amateur radio club, K3ARS, would be able to provide us with 70cm receivers, as they have a repeater on 449.175 Mhz (-) PL 156.7.
Apparently, the most common band for APRS in the US is 2 meters. (144.390Mhz)
We should be able to design an APRS audio generator based on the GPS output using our embedded computer. Getting it to work with an RF transmitter, however, may require the use of a spectrum analyzer, a VCO.
We need to use a circularly polarized antenna on the payload so that the polarization of the beam antenna (a three element Yagi has a 66 degree wide primary radiation lobe) doesn't affect the signal. A 90 degree mismatch in polarization causes a 30 dB loss.
A Quadrifiliar Helix is a compact antenna with circular polarization.
The NEMA 0183 standard is the protocol for GPS output. It outputs one sentence a second, and a sentence contains up to 80 ASCII characters. At one byte per ASCII character, that's a data rate of 80 bytes/second, or 640 baud - which is within the APRS-on-2-meters standard of 1200 baud. NEMA 0183
AGWPE - uses computer soundcard to decode APRS audio, used for testing.
DireWolf - A new APRS decoder that is infinitely better than AGWPE - better GUI, simpler configuration, better defaults...