US commercial satellites and other countries' launches have their own transmission needs and use spot frequencies across the S-band spectrum that sometimes seem quite random as they try to fit in between all the other satellites in orbit.

There are twenty SGLS channels in total but some appear to be currently unused, or it may simply be that nothing has been detected recently.

Uplinks are in the L-band part of the spectrum with associated downlinks at S-band. Some satellite constellations have almost exclusive use of certain of the SGLS channels (eg - the SDS satellites in HEO and geosynchronous orbit appear to use only Channel 9).

Two NOAA satellites have been detected transmitting at the SGLS Channel 10 frequency. One, NOAA 11 is defunct and has an uncontrolled and faulty transmitter. The other, NOAA 19, is quite healthy. 2247.5 MHz is the frequency allocated to the STX4 transmitter aboard all recent NOAA satellites so patient listening may unearth the other active satellites when switched on occasionally. NOAA communicates with a civilian tracking system rather than SGLS.

NASA's AIM satellite also uses the frequency of an SGLS channel but it probably does not operate in SGLS mode.

All three of these satellites are listed here because of the frequency, not because they use SGLS.

The table lists satellites using SGLS frequencies in ascending numerical order. Note that the actual frequencies tend to differ slightly from the nominal values for each channel. Satellites are also seen to drift in frequency according to the amount of sunlight falling on the solar cells. This is particularly obvious around the equinoxes when geosynchronous satellites experience periods of eclipse.