Vaisala RVP900

Chapter 7 __________________________________________________ Host Computer Commands
VAISALA______________________________________________________________________ 275
The SNOISE command should be reissued, now and then, to compensate
for drift in the RF and A/D systems. However, because DC offsets do not
propagate into the "I" and "Q" values, reissuing the command is much less
critical than with the RVP6. The noise levels must be measured for the
RVP900 to properly process data. This can be done by issuing the SNOISE
at least once after power-up, or by setting the correct values for the
power-up noise levels with the Mt setup command (see Section 4.2.5
Mt<n>— Triggers for Pulsewidth #n on page 117). The RVP900 does not
automatically take a noise sample as part of its initialization procedure.
The measured offsets are stored internally for all subsequent uses inside
the RVP900. The offset values may be inspected through the GPARM
command, as may the current range and rate values themselves. Whenever
the range or rate are changed, the user must make sure that the new trigger
rate allows at least 32 km following the new noise range. If this
requirement is not met, or if other failures are detected during the noise
measurement, appropriate bits are set in the GPARM latched status word.
This word should generally be checked after SNOISE to make sure that
everything worked properly.
0916-102
Rng If 1, then the range in input word 1 is taken as the starting
noise range for this and all subsequent SNOISE calls.
Rat If 1, then the trigger rate in input word 2 is taken as the
noise rate for this and all subsequent SNOISE calls.
Action Specifies what action is carried out by the command.
0 Compute a new noise sample based on the present IFD
input signals.
1 Do not compute a noise sample, but rather, read new noise
values from the host computer and use them for subsequent
processing. Four additional input words supply the noise
information, and GPARM words 6, 9, and 44 to 50 are
changed to reflect the new noise settings.
If the current transmit pulse is a hybrid pulse, and XARGS
arguments are supplied, then the additional arguments set
the noise level for the second pulse.
2 Do not compute a noise sample, but rather, restore the
powerup noise defaults.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
| | | | | | | | | | | | | | | | |
| |Action |Rat|Rng| | 0 0 1 0 1 | Command
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