Luca Parmitano KF5KDP on Expedition 36 EVA July 9, 2013- Image credit ESA

ESA astronaut Luca Parmitano KF5KDP has been making random voice contacts from the International Space Station (ISS) to other radio amateurs on Earth on 145.800 MHz.

When the astronauts put out a CQ call, in range of Europe and Africa, they transmit on 145.800 MHz FM but operate “split” listening for replies 600 kHz lower on 145.200 MHz. If you are lucky and hear them calling CQ just remember to activate your rigs repeater shift to ensure you reply on the correct frequency. You should never transmit on 145.800 MHz.

The International Space Station is traveling around the Earth at over 28,000 Km/h. This high speed makes radio signals appear to shift in frequency, a phenomenon called Doppler Shift.

This Doppler shift will cause the ISS transmit frequency of 145.800 MHz to look as if it is 3.5 kHz higher in frequency, 145.8035, when ISS is approaching your location. During the 10 minute pass the frequency will move lower shifting a total of 7 kHz down to 145.7965 as the ISS goes out of range. To get maximum signal you ideally need a radio that tunes in 1 kHz or smaller steps to follow the shift but in practice acceptable results are obtained with the radio left on 145.800 MHz.

In the UK we use narrow 2.5 kHz deviation FM but the ISS transmits using the wider 5 kHz deviation used in much of the world. Most rigs can be switched been wide and narrow deviation filters so select the wider filter. Hand-held rigs all seem to have a single wide filter fitted as standard.

You can receive the ISS outdoors using a 2 metre hand-held with its helical antenna but a 1/4 wave whip will give far better results.

For the current status of the amateur radio stations on the ISS see http://www.issfanclub.com/

Cor PD0RKC reports “On Monday, August 5, 2013 I had a short contact with Luca, anyone made an audio recording? Please send it to my e-mail address see QRZ.com. Thanks in advance!”