User Manual - TRS-RenTelco

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8. Disconnect the MIU CH4 coaxial cable from the VM5000. All of the MIU
LEDs, including Power, will extinguish, but the MIU is still receiving power
to conduct this test. Connect the MIU CH4 coaxial cable to the cable coming
from the analyzer input, using the BNC female/female adapter. To do this,
the latching ring must be rotated to the full clockwise position, as viewed
from the pin-side of the probe housing. Then carefully insert the BNC
adapter, noting the location of the slots for the BNC “ears”.
NOTE. Take care not to short the probe housing pins to the BNC adapter shell
while inserting it. Momentarily shorted pins will not damage the MIU, but can
cause it to change operating mode.
9. Connect the cable coming from the tracking generator and 6 dB attenuator to
the MIU H input BNC.
10. Using Hyperterminal, send the query $LOAD? to the MIU. Verify that you
receive the response: load=0110000. This checks that the MIU operating
mode did not change as a result of disconnecting the CH4 coaxial cable.
NOTE. If the string is not correct, send the command $LOAD=0110000 to the
MIU.
11. Decrease the analyzer Reference Level by 34dB from the Reference Level
selected in step 5. For example, if the Reference Level is –6 dBm, then
decrease it to –40 dBm. The frequency response of the H channel should be
visible in approximately the same position as was the normalized display of
step 6.
NOTE. Take care in identifying the correct signal trace. On many analyzers two
traces, the H channel frequency response with and without normalization, will
be visible. The proper signal trace is the one that is closest to the position of the
normalized display of step 6.
12. Measure the loss difference between low frequency (far left side of trace) and
that at 320 MHz. The measurement method will vary with analyzer model.
Many analyzers have amplitude cursor modes to simplify this type of
measurement. Usually the most accurate way to make this measurement (and
the method to use for an analyzer without amplitude cursor modes) is to vary
the analyzer Reference Level:
a. Using the fine Reference Level adjust, position the left side of the signal
trace to a convenient reference line (such as a graticule line or marker).
Note the Reference Level reading.
VM5000 Automatic Video Measurement Set Option VGA Read This First 21