Xylem System 5000 User Manual User Manual

Page 73

Outputs

At times a user must look at the raw data sent from the satellite to see if things are working

properly. The first part of the message is very important to understand as it may help identify

problems at a site. Below is an actual message sent from a site.
163708DE08078184903G51+1NN021EUB00023BCT@DZ@DY@Dc@Db@Dm@Dxj

Let’s break this down to understand it better. The first 8 characters are the transmitter ID or DCP

address. They are shown in bold below.
163708De08078184903G51+1NN021EUB00023BCT@DZ@DY@Dc@Db@Dm@Dxj

The next two bytes are the year. In this case the 08 is for 2008.
163708DE08078184903G51+1NN021EUB00023BCT@DZ@DY@Dc@Db@Dm@Dxj

The next 3 bytes are the Julian day. In this case 078 is March 18th, on a leap year.
163708DE08078184903G51+1NN021EUB00023BCT@DZ@DY@Dc@Db@Dm@Dxj

The next 6 bytes is the time the transmission was received. This should be within the assigned

time window. In this transmission it was at 18 hours, 49 minutes and 03 seconds.
163708DE08078184903G51+1NN021EUB00023BCT@DZ@DY@Dc@Db@Dm@Dxj

The next byte indicates if the transmission was received properly; the G indicates Good. Other

possibilities are P for parity errors and ? for unknown errors.
163708DE08078184903G51+1NN021EUB00023BCT@DZ@DY@Dc@Db@Dm@Dxj

The next two bytes show the signal strength of the signal received at the satellite. In this case it

is 51 which is quite good. Numbers in the high forties are also good; lower forties is fair and 35

or less is surprising to see the transmission making it to the satellite.
163708DE08078184903G51+1NN021EUB00023BCT@DZ@DY@Dc@Db@Dm@Dxj

The next two bytes indicate if there is any frequency drift. A plus 0 is ideal indicating no drift.

In this case the +1 indicates a positive drift of 50 Hz from the center frequency. For each count,

1, 2, 3 etc it refers to 50 Hz per count of drift. A drift of 1 or 2 positive or negative is common.
163708DE08078184903G51+1NN021EUB00023BCT@DZ@DY@Dc@Db@Dm@Dxj

The next two bytes indicate modulation status. The NN indicates normal modulation index, and

normal modulation quality. The index may also report an H or L for high or low modulation

index. The quality may also report F or P for fair or poor quality.
163708DE08078184903G51+1nn021EUB00023BCT@DZ@DY@Dc@Db@Dm@Dxj

Deciphering Downlink Message Headers