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Modulated Antenna User Manual - Prelim3
Page 7 of 10
Printed: 11/16/22
3:39 PM
RECEIVING UHF SIGNALS
After the TPM stem receives the wake up signal it will transmit a UHF data package. The stems transmit data in
one of two frequency bands 315 MHz and 433 MHz bands depending on the stems design. Typically, 315 MHz is
used in the U.S. and 433 MHz is used in export vehicles. The frequency used is governed by the FCC in the
United States. Vehicle’s being sold in other countries will be governed by that country’s RF communications
governing body.
Like the Modulated LF message structure, the basic unit for a UHF transmission is a packet. This packet will be
coded in a similar way that the LF data was coded. After a valid wake up signal is received by the stem, it will
typically transmit the same data packet several times in “bursts”. The number of packets in a burst varies from
stem to stem. It can even vary for a single stem type, based on the mode the stem is in. With all the different
stems that have been observed to date, the number of bursts can be in as few as 4 packets repeated to as many
as 16 packets. Repetition of the packets helps ensure the highest probability that data will be received. Also,
receiving the same packet multiple times helps ensure that the data was received correctly, not some falsely
interpreted noise.
