Operating Instructions
1705A Spectrum Monitor 2-7
Measurement Graticule
The 1705A is equipped with aninternal graticule crt. The graticulehas an 8 X
10 division scale that is lighted. Scalebrilliance is controlled by the front-panel
SCALE control. Figure2-4 shows the 1705A graticule. Refer to this figure and
subsequent figureswhen reading the following discussion of the graticule.
Tek
REF
--10
--20
--30
--40
--50
--60
--70
L
O
G
+f
Figure2 -4: 1705A graticule scale
The verticalscale is eight divisions in height. The center vertical scale is broken
into five equal minor divisions per major division. Notethat the 0 dB reference
is at the top of the graticule and that 80 dB (maximum division) is at the bottom
of the graticule. There are two gain selections: normalgain (10 dB/div) and
high gain (2 dB/div). Innormal gain mode, major divisions are 10 dB, which
makes each minor division 2 dB. When the GAIN front-panel push butt on is
held, high gain is selected,and major divisions are approximately 2 dB, which
makes minor divisions about0. 4 dB each.
Since dB is a dimensionless ratio, and there are severalscale variations, it is
essential that therebe some discussion of the various scales. The unit of
measure described as dB (decibel) is 10 LOG P1/P 2. Ifthere is a specific scale
defined (m, k, w, p, etc.), there is a specific reference point established. The
1705A has input specificationsin dBm, which means that they are referenced to
1 mW (milliwatt). Therefore, --30dBm is 30 dB below 1 mW. Table2--1is a
handy referencetable for dB and dBm. Table 2--2provides a reference for
conversion fromdBm to v.

VerticalScales