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AT
Attenuation
The AT command specifies the RF input attenuation from B to 70 dB, in 10 dB steps.
The input attenuator is coupled to the reference level. This coupling keeps the mixer input level at or below a
threshold, when a continuous wave signal is displayed on the spectrum analyzer screen with its peak at the refer-
ence level. Instrument preset (IP) sets the threshold value to - 10 dBm. (See KS, and ML.)
The AT command allows less than the threshold value at the mixer input. Executing CA (couple attenuator) resets
the attenuation value so that a continuous wave signal displayed at the reference level yields - 10 dBm (or the
specified threshold value) at the mixer input.
When the attenuation is changed with the AT command, the reference level does not change. Likewise, when the
reference level is changed with the RL command, the input attenuation changes to maintain a constant signal level
on screen.
The following program lines illustrate proper syntax:
10 OUTPUT718;"AT60;"
20 OUTPUT718;"ATUP;"
Sets attenuation to 60 dB.
Line 10:
Line 20:
Sets attenuation to 70 dB.
When queried (OA or ?), AT returns the attenuation value as a real number, followed by a carriage-return/line-
feed (ASCII codes 13, 10). The end-or-identify state (EOI) is asserted with line feed.
Refer to Chapter 8 in Section I.
3 0 P r o g r a m m i n g
AT
real
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