Changes to AO-51 CTCSS access tone

This week, Drew Glasbrenner KO4MA, AMSAT-NA VP Operations reported that the CTCSS 67 Hz sub-audible tone used on AO-51's uplink to enable the FM transponder has been turned off. Carrier access is all that is required to access this satellite.

Drew explained further, "The 67 Hz tone was originally designed to allow AO-51's downlink to be switched off when the satellite was not in use.

The use of the subaudible tone access has been problematic over areas of heavy use and when trying to identify the seemingly growing interference issues experienced on the 2 meter uplink frequency."

Access into AO-51 is expected to improve worldwide. Despite the near ubiquity of subaudible tone enabled radios in North America, many areas of the world have limited or difficult access to this type of equipment, even in commercial off-the-shelf gear. Carrier-access enables amateur radio
operators in these areas to use the satellite.

Drew concluded, "Full duplex operation is the most courteous and efficient means of operating the FM satellites. This allows you to listen to the downlink before you transmit as well as when you transmit to reduce QRMing other users. Also, please continue with renewed vigor to help identify and
eliminate both non-amateur interference, and amateurs operating outside of the established bandplan that interfere with our satellites."

Drew, KO4MA

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