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1. RADAR OPERATION
1-32
1.20.2 Measuring range by the variable range marker (VRM)
There are two VRMs, No. 1 and No. 2, which appear as dashed rings so that you
can discriminate them from the fixed range rings. The two VRMs can be
distinguished from each other by different lengths of dashes.
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No. 1
VRM
Target
blip
No. 2
VRM
VRM1
VRM2
>0.66NM<
1.18NM
45:02
99:59
TTG to VRM
Measuring range with VRMs
By keyboard
1. Press the [VRM ON] key to display either of the VRMs. Successively
pressing the [VRM ON] key toggles the active VRM between No. 1 and No. 2.
The currently active marker is enclosed with >.....<.
2. Operate the VRM rotary control to align the active variable range marker with
the inner edge of the target of interest and read its distance at the lower-right
corner of the screen. Each VRM remains at the same geographical distance
when you operate the [RANGE] key or the RANGE box. This means that the
apparent radius of the VRM ring changes in proportion to the selected range
scale.
3. Press the [VRM OFF] key to erase each VRM.
By trackball
1. Roll the trackball to place the arrow in the VRM1 or VRM2 box, whichever
VRM you want to use.
VRM1
VRM2
VRM boxes
2. The guidance box reads “VRM ON/.” Push the left button to turn on the VRM.
The guidance box now reads “VRM SET L = DELETE /.”
3. Push the left button again and the cursor jumps to inside the effective display
area. The guidance box now reads “VRM FIX / EXIT.”
4. Roll the trackball (coarse adjustment) or wheel (fine adjustment) to align the
active variable range marker with the inner edge of the target of interest and
read its distance at the lower-right corner of the screen. Each VRM remains
at the same geographical distance when you operate the [RANGE] key. This
means that the apparent radius of the VRM ring changes in proportion to the
selected range scale.
5. Push the left button to anchor the VRM and fix its readout, or push the right
button to return the VRM to its previous location (range).
6. To erase a VRM, choose the appropriate VRM readout box and then push
the left button until the VRM disappears from the screen.