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Model 11848 A
A7 10 MHz Modulated VCXO B Assembly
The 10 MHz ±1 kHz VCXO (voltage controlled crystal oscillator) provides a clean, tuneable source
available at the front-panel 10 MHz B connector. This source can be used as a tuneable VCO for
measurement of 10 MHz sources or in conjunction with the 10 MHz ±100 Hz VCXO in A6 for
demonstration purposes. It can also be phase modulated by the Phase Modulator for testing phase
noise accuracy in the system performance tests.
A8 400 MHz VCO Assembly
The 400 MHz VCO provides a clean, wide-range, tuneable source available at the front-panel 350-
500 MHz connector. This source can be used as a tuneable VCO for measurement of 350-500 MHz
sources or in conjunction with the 400 MHz Oscillator in A9 to test flatness in phase-noise measurement
or by itself for noise-floor testing using a power splitter and delay line.
Pad 1, Amplifier 1, Pad 2, Amplifier 2, and Amplifier 3 provide the correct level to the front-panel
connector for driving the input phase detector. The 550 MHz Low-Pass Filter removes harmonics of
the signal.
A9 400 MHz Oscillator Assembly
The 400 MHz Oscillator provides a fixed source available at the front-panel 400 MHz connector.
The 50 dB Pad lowers the signal level to reduce the signal-to-noise ratio. The Amplifiers boost the
signal level back up but also add noise of their own. This source is primarily used in conjunction with
the 350-500 MHz VCO in A8 to check the flatness of the broadband noise beyond 500 kHz or for
demonstration purposes.
A1 HP-IB Input/Output Assembly
The Al HP-IB Input/Output Assembly (not shown in the block diagram) contains the digital circuitry
to interface the controllable hardware with the controller via HP-IB. It also contains the power supplies.
The power supplies are +5V, 4-15V, and —15V.
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