B&K 4071 Input gain, External AM Mode Parameters, Input Gain, Carrier Frequency, PEP Level

5.3 External AM Mode

Introduction

External AM mode generates amplitude-modulated signal of fixed carrier frequency, were externally supplied signal is used as a modulating signal to vary signal modulated frequency and depth. Modulated frequency, output level, input gain and DC offset values could be manually entered from the front panel keypad in this mode. External signal gating options is available in this mode. External AM mode could be entered by pressing “Mode”> “AM” >”2” key at any time.

External AM Mode Parameters

The External AM mode has the following front panel display:

1	External AM	Input gain: .999
	1,000,000.00 Hz	PEP level: -10.0 dBm
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Figure 5.3-1: External AM mode display

1. Input Gain

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In this field specify a value used to scale the input signal. With a value of .999, a 1 Vp -p signal on the input will result in 100% modulation of the carrier amplitude. You may enter a value from 0 to .999. (The gain value is always less than 1.0).

To enter a value, type 1 to 3 numeric digits. If you type 3 digits, the value is automatically entered. If you only type 1 or 2 digits, you can press the MHz key or the KHz key or the Hz key (all are equivalent) to enter the gain value.

2. Carrier Frequency

In this field enter the frequency of the carrier, from 0 Hz (DC) to 31.5 MHz in 0.01 Hz steps.

3. PEP Level

In this field enter the output level, from 4 mVp -p to 5 Vp -p in 1mV steps or from -44.0 dBm to +18.0 dBm in 0.1 dBm steps.

NOTE: The level specified in External AM mode is the Peak Envelope Power, or PEP. As a peak-to-peak value, this level represents the maximum peak-to-peak voltage swing that will result from a 100 percent modulated carrier. If no modulating signal were applied, the unmodulated carrier would have only half the peak-to-peak swing of a 100% modulated carrier.

NOTE: The level specified is a 50O loaded level. This is the level of the signal, which will appear across a 50O load connected to the SIG Out connector. Into an open circuit, the output swing will be twice the value entered.

Offset

You can enter an offset voltage for the output signal. For more information on output offsets refer to section 4.4.

Ext Gating Input

This TTL compatible input can be used to gate the output signal on or off. A logic high voltage turns off the output. For further information on the Ext Gating Input, refer to section 2.0.

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BK Precision 4071 User Manual Rev.2.2