Satellites in HEO - 'Molniya' type orbit - are used by the US for slow speed radio teletype (RTTY) communications using FSK (Frequency Shift Keying) The downlink signals are easily discernable. Transmissions have been reported also from satellites in geosynchronous orbit but they are not detectable in the UK because the supposed transmitting satellites are below the horizon when viewed from here
There are unsubstantiated reports that the uplinks can be intercepted in some parts of the continental United States.
As of 2006 June, downlink channels 1-8 and 10-12 were carrying RTTY links, some with frequency shift of approximately 2.7 kHz and some with approximately 2.1 kHz. Channel 9 had a single carrier, making it very useful for measuring the Doppler shift.
From time to time, the transmit frequency is shifted downwards (approx 168 second intervals) by about 20 Hz in order to counteract the changing Doppler shift experienced by ground stations.
Freq (MHz) |
Satellite |
Payload |
Signal Type |
Notes
|
243.695 |
USA-137 (SDS-3 F1)
1998-5A
25148
90025 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 1 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
Early in 2007, USA-137 ceased to transmit AFSATCOM |
243.695 |
USA-125 (SDS-2 F4)
1996-38A
23945
90028 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 1 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
2007 Oct 15, USA-125 ceased to transmit AFSATCOM |
243.705 |
USA-137 (SDS-3 F1)
1998-5A
25148
90025 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 2 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
Early in 2007, USA-137 ceased to transmit AFSATCOM |
243.705 |
USA-125 (SDS-2 F4)
1996-38A
23945
90028 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 2 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
2007 Oct 15, USA-125 ceased to transmit AFSATCOM |
243.710 |
USA-137 (SDS-3 F1)
1998-5A
25148
90025 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 3 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
Early in 2007, USA-137 ceased to transmit AFSATCOM |
243.710 |
USA-125 (SDS-2 F4)
1996-38A
23945
90028 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 3 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
2007 Oct 15, USA-125 ceased to transmit AFSATCOM |
243.715 |
USA-137 (SDS-3 F1)
1998-5A
25148
90025 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 4 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
Early in 2007, USA-137 ceased to transmit AFSATCOM |
243.715 |
USA-125 (SDS-2 F4)
1996-38A
23945
90028 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 4 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
2007 Oct 15, USA-125 ceased to transmit AFSATCOM |
243.720 |
USA-137 (SDS-3 F1)
1998-5A
25148
90025 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 5 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
Early in 2007, USA-137 ceased to transmit AFSATCOM |
243.720 |
USA-125 (SDS-2 F4)
1996-38A
23945
90028 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 5 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
2007 Oct 15, USA-125 ceased to transmit AFSATCOM |
243.725 |
USA-137 (SDS-3 F1)
1998-5A
25148
90025 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 6 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
Early in 2007, USA-137 ceased to transmit AFSATCOM |
243.725 |
USA-125 (SDS-2 F4)
1996-38A
23945
90028 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 6 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
2007 Oct 15, USA-125 ceased to transmit AFSATCOM |
243.730 |
USA-137 (SDS-3 F1)
1998-5A
25148
90025 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 7 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
Early in 2007, USA-137 ceased to transmit AFSATCOM |
243.730 |
USA-125 (SDS-2 F4)
1996-38A
23945
90028 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 7 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
2007 Oct 15, USA-125 ceased to transmit AFSATCOM |
243.735 |
USA-137 (SDS-3 F1)
1998-5A
25148
90025 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 8 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
Early in 2007, USA-137 ceased to transmit AFSATCOM |
243.735 |
USA-125 (SDS-2 F4)
1996-38A
23945
90028 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 8 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
2007 Oct 15, USA-125 ceased to transmit AFSATCOM |
243.740 |
USA-137 (SDS-3 F1)
1998-5A
25148
90025 (classfd.tle) |
Military quick reaction comms |
Channel usually occupied by an unmodulated carrier |
AFSATCOM Channel 9 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
Early in 2007, USA-137 ceased to transmit AFSATCOM |
243.740 |
USA-125 (SDS-2 F4)
1996-38A
23945
90028 (classfd.tle) |
Military quick reaction comms |
Channel usually occupied by an unmodulated carrier |
AFSATCOM Channel 9 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
2007 Oct 15, USA-125 ceased to transmit AFSATCOM |
243.745 |
USA-137 (SDS-3 F1)
1998-5A
25148
90025 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 10 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
Early in 2007, USA-137 ceased to transmit AFSATCOM |
243.745 |
USA-125 (SDS-2 F4)
1996-38A
23945
90028 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 10 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
2007 Oct 15, USA-125 ceased to transmit AFSATCOM |
243.750 |
USA-137 (SDS-3 F1)
1998-5A
25148
90025 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 11 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
Early in 2007, USA-137 ceased to transmit AFSATCOM |
243.750 |
USA-125 (SDS-2 F4)
1996-38A
23945
90028 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 11 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
2007 Oct 15, USA-125 ceased to transmit AFSATCOM |
243.760 |
USA-137 (SDS-3 F1)
1998-5A
25148
90025 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 12 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
Early in 2007, USA-137 ceased to transmit AFSATCOM |
243.760 |
USA-125 (SDS-2 F4)
1996-38A
23945
90028 (classfd.tle) |
Military quick reaction comms |
CW - RTTY-style data |
AFSATCOM Channel 12 transmission
2005-2007, USA-137 and USA-125 were providing alternating coverage of the northern hemisphere from HEO
Second transmission frequency at 2242.50 MHz
2007 Oct 15, USA-125 ceased to transmit AFSATCOM |
