B&K 4071 user manual Internal FSK Mode Parameters, Mark Frequency, Space Frequency

5.9 Internal FSK Mode

Introduction

Internal FSK mode generates a frequency shift keyed signal of fixed amplitude. Internal timer is used as modulating signal to toggle the output signal frequency between mark frequency and space frequency. Mark and Space frequencies, output level, modulating shift frequency and DC offset values could be manually entered from the front panel keypad in this mode. External signal gating option is available in this mode. Internal FSK mode could be entered by pressing “Mode”> “FSK” >”1” key at any time.

Internal FSK Mode Parameters

The Internal FSK mode has the following front panel display:

1	Int FSK: 1,000 Hz	Mark: 1,000,000.00 Hz
	Space: 2,000,000.00 Hz	-10.0 dBm
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Figure 5.9-1: Internal FSK mode display

1. Modulating Frequency

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In this field enter the frequency at which the output will switch between the Mark and Space frequencies. You may enter from 0 Hz to 130,000 Hz in 1 Hz steps. The internal modulating frequency is accurate to 1 Hz from 0 Hz to 3900 Hz. It is accurate to within 1% across its full range of 0 Hz to 130,000 Hz.

2. Mark Frequency

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

3. Space Frequency

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

4. Level

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

NOTE: For wideband FSK (where the difference between Mark and Space frequencies is > 1.0 MHz), the output level may shift slightly between the mark and space frequencies. The 4071 has internal leveling circuitry, which is disabled in this mode, in order to offer higher FSK modulation rates.

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