Ham Radio Forum

Frequencyes used by cubesat transmitters
(cubesat = a small sattelite usually weighing 1 -3 kg)

I am looking for an UHF cubesat transmitter able to sustain, continuously, data rates of at least 115 200 bps from a 300 - 400 km orbit. Total available power for transmission is 1 W (this is a critical restriction), maximum weight including antenna should not be more than 400 g.
I have found a list of frequencies, baud rates, communication protocols used by cubesats but unfortunately most of them are characterized by extremely low baud rates with a few doubtful exceptions not in UHF band.

Question: Is it physically possible to build a transmitter with the characteristics mentioned above or not? Are other bands (utilized preferably by radio amateurs) more suitable for high speed transmissions?

There are both legal and technical issues associated with what you want to do.

Legal Issue
The RF signal transmission bandwidth of a radio signal increases as the data bandwidth of the modulating signal is increased. The RF signal transmission bandwidth that would result from sending data at 115,200 bps would greatly exceed rules and regulations of the FCC and other world regulators at the Cubesat transmission frequencies listed in the table you referenced: http://cubesat.ifastnet.com/forum/download/file.php?id=66

Technical Issues
Technical difficulties associated with transmitting wideband data by radio vary inversely as a function of the ratio of data bandwidth to RF transmission center frequency. It is technically easy to send extremely wide bandwidth data if the RF transmitter center frequency is also extremely high, but doing that becomes increasingly difficult at lower RF transmission frequencies. Unfortunately, it becomes increasingly difficult to efficiently convert DC power to RF power as the transmission center frequency is increased.

The baud rates listed in the Cubesat transmitter summary table are low due to these issues.

Andy