Vaisala RVP900, User Manual

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The (
I
,
Q
) time series data from the IFDR are transmitted to the host computer through
Ethernet UDP packets. Depending on the receiver configuration (dual-pol, bin spacing, and
so on.) the time series data rate may be as high as 50 MB/second. To improve the efficiency
of packet transmission and reception, use jumbo packets, that is, packets that are longer
than the typical 1500-byte standard. RVP900 allows jumbo packets up to 8192 bytes.
Limits: 250 ... 8192 bytes. Use, for example,
ifconfig mtu 8192 eth0
to set the
receiver Maximum Transfer Unit size on the host computer. You must also configure
any inline Ethernet switches to transmit the jumbo packets.
Maximum ethernet incoming UDP frame length : 8192
The UDP time series packets are send-and-forget, meaning that the IFDR assumes that
every transmitted packet is correctly received by the RVP900 host computer. This
assumption is reliable as long as there is sufficient buffering of the incoming data to prevent
overruns within the Linux environment. Usually the 1.5 MB default provides reliable
reception, but this can be increased to 5 MB if
UDP acquisition ID mismatch errors
are listed in the RVP900 diagnostic log.
Limits: 100000 ... 5 000 000 bytes
Receive buffer size for incoming UDP packets : 1500000
This is the frequency of the acquisition sampling clock in the IFDR module. The clock is
synthesized on-board using a low-jitter PLL that allows any frequency to be generated
merely by choosing it here to the nearest 0.1 Hz.
Limits: 50 MHz ... 100 MHz
IFD synthesized system clock: 72.0000000 MHz
The synthesized system clock can be derived from an internal crystal oscillator or from an
externally applied reference clock. When the external source is used, its frequency is
specified here.
IFD clock is derived from an external reference: YES
External input reference: 10 MHz
This setting is used to configure the input of live antenna angles. If angle data are supplied
outside RVP900, for example by an RCP8 making direct calls to the IRIS antenna library,
then select
None . For test purposes, the SimRVP and SimIFD options implement an
antenna simulator either in the host computer or the remote IFDR. Parallel angle inputs can
be used through TAGs, and 3-wire synchros can hookup using the S/D option.
Select
RtCtrl
when custom software has been written to deduce antenna angles from the
real–time state machine controller.
Chapter 5 – TTY Non-volatile Setups
103