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Author Topic: Amtrak ACSES II at 217 MHz  (Read 526 times)

Offline radio_FSK

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Amtrak ACSES II at 217 MHz
« on: April 18, 2024, 2102 UTC »
This is an ACSES II signal at 217MHz

Please note the radio is being bombarded with an extremely strong signal as this was captured from only 1 mile away. The SDR causes strong signals to be duplicated along the capture space.

Some data appears to be known about ACSES II signals: https://www.sigidwiki.com/wiki/Advanced_Civil_Speed_Enforcement_System_(ACSES_II)

Messaging standard ATCS 200 appears to be correct as referenced in Siemens technical documents.
No idea how the baud rate 9600 is known.

Consult this channel listing as well: https://www.radioreference.com/db/subcat/89094
South of New Haven applies for where this was captured. ACSES S1 channel appears to be the one audible here.

Please let me know what kind of data mode this is. My guess is 4-level FSK but I don't know enough to be sure. My goal is to write a program to decode these signals. In a conversion to audio I can see what appears to be a bit sync for 68 bits (assuming 9600 baud) preceding each message.