Operation Overview
3-24
EXT REF I N
5Y��AK@
l or.t1 z REF
OUTPUT
I F OUTPUT
Model 3585A
The EXT REF IN input allows the 3585A's master oscillator to be
phase locked to the internal Oven Reference or an external frequency
standard. The input is ac coupled and the input impedance is 50
ohms. The frequency of the reference signal applied to this input
must be 10 MHz or any subharmonic down to 1 MHz ( ± 5 ppm), and
the amplitude must be within the range of 0 dBm to + 1 5 dBm (50
ohms). Dynamic range performance will be degraded unless the
phase noise and spurious content o f the reference signal
is
s
- l lOdBc (1 Hz) referred to 10 MHz at a 20 Hz to 1 kHz offset.
To use the internal Oven Reference, connect this BNC-to-BNC
jumper between the OVEN REF OUT connector and the EXTER
NAL REF IN connector.
The 10 MHz REF OUTPUT supplies a 10 MHz square wave that is
phase locked to the reference frequency applied to the EXTERNAL
REF IN connector. When the internal Oven Reference is used, the
frequency accuracy is 10 MHz ± 1 x 1 0 - 7 per month. The output is
transformer coupled, the output impedance is 50 ohms and the
nominal output level is + 20 dBm/50 ohms. This reference output
can be used to phase lock an external signal source or another
analyzer to the 3585A's frequency reference.
The IF OUTPUT is taken from a voltage divider which connects
directly to the output of the 3585A's final IF filter. The output signal
is a 350 kHz (nominal) sine wave, whose amplitude is linearily pro
portional to the amplitude of the input-signal component to which
the 3585A is tuned . The output is ac coupled and the output im
pedance is approximately 450 ohms. When the signal amplitude is
equal to the Reference Level and the Reference Level is + 10 dB to
- 56 dB relative to the Range setting, the full-scale IF output level
ranges from approximately 247 mV rms ( - 12.0 dBV) to 1 57 mV
rms( - 1 6.0 dBV), depending on the internal IF gain setting. The IF
gain settability is limited to 4 dB steps and, because of the variable
offsets that are introduced by the Automatic Calibration system, the
IF gain and full-scale IF output level is not always the same for a
given Reference Level setting. The full-scale IF output level will vary
(over a 4 dB range) as a function of Reference Level, Range, Im
pedance and Resolution Bandwidth. Before using the IF Output in a
critical measurement application, select the required operating
parameters, force an Automatic Calibration and then
measure
the
full-scale IF output level.
The IF Output can be used to drive an external detector (e.g., a
voltmeter or wave analyzer) to obtain a linear video output which, in
turn, can be used for audio monitoring in radio surveillance applica
tions, or applied to the vertical input of a storage 'scope or X-Y
Recorder for applications requiring a linear amplitude scale. The IF
Output can also be connected to a true rms voltmeter, such as the
-hp- Model 3403C, for making rms noise-level measurements.
