Signal strengths of the two ISS ham radio stations

International Space Station ISS with shuttle Endeavour 2011-05-23

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).

Expedition 5 flight engineer Peggy Whitson KC5ZTD holds one of the two amateur radio antennas in the Unity node on the ISS. The antennas were installed during a spacewalk scheduled on August 22, 2002

Expedition 5 flight engineer Peggy Whitson KC5ZTD holds one of the two ISS amateur radio antennas installed on the Russian Service Module August 22, 2002

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).

FUNcube Dongle Software Defined Radio

FUNcube Dongle Software Defined Radio

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)

Russian Service Module amateur radio antennas
Also see

Astronaut Radio Amateurs

PA3GUO website