User's Manual

RVP8 User’s Manual
October 2005
TTY Nonvolatile Setups
3–35
3.3 Advanced Options
3.3.1 * — Sample current noise levels
The “*” samples current noise levels from the receiver and then subtracts that noise from
subsequent measurements. More information is provided in the Sample Noise Level (SNOISE)
section 6–6.
3.3.2 @ — Display/Change current Major Mode
This command provides developers with a simple way of switching modes enabling on–the–fly
testing of code. The top level RVP8 operating modes are described in the documentation of the
SOPRM command word #9. This question allows you to use the mode that has been selected by
that command, or to force the use of a particular mode.
3.3.3 ~ — Burst-In / IF-In Swap Command (Rev.D IFD)
The “~” command swaps the Burst and IF inputs at the IFD. Requests to toggle the state are
made from the top level as follows:
RVP8> ~
IFD Burst/IF Inputs are: SWAPPED
RVP8> ~
IFD Burst/IF Inputs are: NORMAL
The selection remains in effect for the duration of the setup session, but then returns to
NORMAL upon exiting the TTY monitor. The “~” command is very handy because it allows
the Pb, Pr, and Ps plotting commands to easily run with one input or the other. Here are two
examples of how this might be useful.
S When checking the range alignment on a Klystron system, the Pb plot can not be used in
the usual way to center the Tx burst because a continuous-wave COHO (rather than a
burst pulse) is typically used as the phase reference in these systems. However, if you
swap the Burst and IF inputs, you can then use the Pb command to view and center the
received leakage of the Tx pulse, and thus locate range zero.
S When setting up the AFC loop, you can use your RF signal generator to simulate the
transmitter’s frequency, and then run the loop with swapped RVP8/IFD inputs. The AFC
servo will then hunt and follow the siggen frequency supplied via the receiver. You can
then make step changes in that frequency to verify that the loop responds properly.
Note that the same input swapping function is also available via the RVP8/IFD toggle switches.
However, those switches may be located far away from the operator’s terminal; hence, the
command interface is still a valuable addition. The “~” command can only be used with a Rev.D
or later IFD; the command is unimplemented, and will not show up in the “Help” list, when
earlier receivers are connected.