Radios, Modes and Antennas on the ISS

The ISS amateur radios are Ericsson MP-X handheld radios, a Kenwood TM D700 and a Kenwood D710.

Two hand-held Ericsson (M-PA Series) transceivers are on board in the ISS Columbus module: a VHF radio that receives and transmits FM voice or packet radio signals in the 2-meter (144 to 146 MHz) Amateur Band, and a UHF radio that receives and transmits FM voice or packet radio signals in the 70 centimeter (435-438 MHz) Amateur Band. Both radios are Ericsson (M-PA) series commercial grade radios. These radios look identical in size and features, but are specially tuned to support the different bands.  Up to 5 Watts of output power is available on any one of 64 possible channels.

The Kenwood TM-D700 radio. located in the ISS FGB Service Module (Zarya), supports 2 meter (144-146 MHz) and 70 cm (435-438 MHz) operation. This radio provides a higher output power capability (restricted to a maximum of 25 Watts in ISS operation) supporting FM and packet operations. The higher power capability allows nearly horizon-to-horizon signal reception using simple hand-held radios or scanners. A set of 5 default options, or Programmable Memories, are embedded in the D700 to support ISS operations.

There are numerous channels programmed in the radios. Two of these channels on the 2 meter radio band support voice operations (145.80 down/144.49 up for ITU Regions 2 &3 & 145.80 down/145.20 up for ITU Region 1). It is necessary to use two uplinks due to region-to-region ITU restrictions on uplink frequencies.

The crew switches between one frequency to the other; scanning is not used. For example, if a crew member begins a QSO over the US, they can track US stations until they hit the Atlantic and then they will quickly lose US stations. They can then switch over to the other frequency and pick up stations in Europe or Africa.