New NOAA 18 satellite frequencies for the WEPIX 2000B

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WEPIX 2000B receiver

The new NOAA satellites, NOAA 18 and NOAA 19 are using new transmission frequencies for APT transmission. The new frequencies, 137.100 and 137.9125 MHz are not programmed into the 2716 EPROM of the WEPIX 2000B receiver, so I have calculated the required programming data for them, as shown in the table below.

Since the design of the WEPIX receiver will only accept frequency steps of 5 KHz or 10 KHz, the new 137.9125 frequency cannot be exactly programmed, so I chose the closest values above and below that frequency. The error is only 2.5 KHz, so either channel should be able to receive the APT signal with minimum degredation. Due to doppler shift, the recption may be slightly better on one channel while the satellite is approaching, and it may be better on the other channel as the satellite moves away from your location.

Bank 2 of the EPROM does not need to be changed, if you are happy with the existing frequency programming.

Channel Frequency EPROM ADDRESS Hexadecimal data
1 137.100 0000 00 0F 04 00 00 08 0C 00
2 137.300 0008 00 0F 04 04 01 08 0C 00
3 137.400 0010 00 0F 04 0E 01 08 0C 00
4 137.500 0018 04 0F 04 00 00 08 0C 00
5 137.620 0020 04 0F 04 0C 00 08 0C 00
6 137.850 0028 04 0F 04 03 02 08 0C 00
7 137.910 0030 08 0F 04 01 00 08 0C 00
8 137.915 0038 00 0F 09 03 00 00 09 01

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