In article ,
says...

low bit rate (sounds a bit like RTTY) transmitter on the ISS on around
149.9xx Mhz? I ask as there is definitely such a transmission and though
I've not checked the times exactly it seems to be around the times one would
expect to be in range of the station from the UK.
The doppler shift variation is very large and very hard to keep in tune
manually.
Its obviously in quite a low Earth orbit as this kind of doppler effect
does not happen on spacecraft up where the weather sats are on 137Mhz.
Its also an unusual freqency to use, often these tend to be russian in
origin from memory.

Unsure of the details, but this is a high level overview for those who
have never heard of this before.

International Space Station Reference
Ham Radio
http://spaceflight.nasa.gov/station/reference/radio/

Jeff
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