Henk Hamoen PA3GUO used his AMSAT-UK FUNcube Dongle Software Defined Radio (FCD SDR) to show the variations in signal strength between the two amateur radio stations on-board the International Space Station (ISS).
The amateur radio station in the Russian Service Module uses a Kenwood D700 transceiver which is understood be on its lowest power setting of 5 watts output and feeds a whip antenna on the Module. When acting as a packet radio digipeater it transmits data on 145.825 MHz.
A second amateur radio station in the European Space Agency (ESA) Columbus Module is usually used for voice communication. It comprises Ericsson handheld transceivers believed to be capable of 5 watts output to a whip antenna on the exterior of the module. When the radio hams on-board the ISS talk to other radio amateurs on Earth they transmit on 145.800 MHz.
Both stations use 5 kHz deviation FM (25 kHz channel spacing).
Henk PA3GUO writes:
FCD SDR recording of ARISS Italy school contact with astronauts onboard the ISS. Purpose is to show the signal strengths of the 2 transceivers onboard ISS: Ericsson Voice transceiver (left) and Kenwood data transceiver (right). At time 11:54z [2013-06-29] my antenna had to turn 180 degrees, signal is lost for a while. Remarkable: at the beginning voice TX signal is strong, even a bit stronger as data TX signal. At the end of the pass data keeps strong, voice fully drops into the noise. Seems the antenna of the Voice [ESA Columbus Module] transceiver is somewhat (more) shielded by the ISS exterior (e.g. solar panels).
29 June 2013, school contact Italy with International Space Station
Frequency: 145.800 + 145.825 MHz
Antenna: 6 elements + 15 meters Aircell coaxial cables
Receiver: FCD SDR + SSB pre-amp (mounted next to the FCD SDR)
Software: HDSDR (SDR receiver) + SatControlFCD (DK3WN freq control)
Watch ARISS Italy ISS SDR recording (speech and data spectrum)
Astronaut Radio Amateurs http://www.w5rrr.org/astros.html
PA3GUO website http://www.pa3guo.com/