Table of Contents
Advertisement
NOTE
The RF protect circuit may trip if generator is run at full power output without having
a 50-ohm load connected.
4-9.
DUPLEX GENERATION. When operating in the duplex generate mode the offset frequency can be set
to either 45 MHz or 0 to 10 MHz (adjustable). The lmage/Dplx switch sets the offset frequency above (high) or
below (low) the monitored frequency. When offset is in the 0 to 10 MHz range, the control range may include a
fold back region. If the generator is operated in this fold back area erroneous frequency output indications can
be given. Avoid areas where backward indication ora jittering display of the offset frequency are incurred. The
following is an example of the duplex generator being used to setup repeater levels.
a.
Connect DUPLEX GEN output to repeater receiver antenna input and repeater transmitter signal
sample to RF In/Out connector. The Duplex Gen Output level is fixed at -30 dBm nominal.
b.
Set FUNCTION switch to Gen and DISPLAY to Duplex Gen.
c.
Select Duplex Monitor frequency (repeater transmit frequency) from memory table or enter directly
from keyboard.
d.
Set DUPLEX GENERATOR frequency to repeater receiver frequency.
e.
Adjust PL and test tone deviation to desired level on display.
f.
Set FUNCTION switch to Monitor and measure the deviation of the repeated signal.
NOTE
Switch function to power monitor and connect repeater transmitter (under 125
watts) directly to the RF In/Out connector to read power and frequency error, as
well.
DUPLEX
RF
OUTPUT
IN/OUT
R·2001A
REPEATER XMIT
FREQUENCY
REPEATED
RECEIVED FREQUENCY
ATER
REPE
RFIN
REPEATER
D•JPLE.< MOll
PDS DEVIATION
RF OUT
REPEATER
NEG DEVIATION
OF RE PEA TED SIGNAL
D
s
EVIATION ALARM-
ETTING
-:.n
LE'' '"'
.;.::
..,._OF REPEATED SIGNAL
~~------~0--~-----.~,,
ri:
~LAFtl 05,0 ·H:
ATTfh ·:
B521·27
Figure 4-5.
Duplex Generation Test Setup and CRT Display
4-10.
FREQUENCY COUNTER.
The frequency counter measures inputs in a range from 10Hz to 35 MHz.
The input to the frequency counter is through the Vert!Sinad/DVM/Counter in, BNC connector (located in the
OSCILLOSCOPE section of the front panel). The counter sensitivity is controlled by the scope Vert switch.
The following shows the minimum sensitivity for each switch setting:
Switch setting
0.01
0.1
1.0
10.0
Sensitivity
50 mV RMS
500 mV RMS
5V RMS
50V RMS
The autorange output of the counter is displayed on the CRT to a resolution of 0.1 Hz or 5 digits.
NOTE
Do not connect transmitter directly to the frequency counter input. Instead use the
RF In/Out connector and the frequency error meter for transmitter frequency
measurements.
4-11.
SPECTRUM ANALYZER.
Input to the spectrum analyzer is through the RF In/Out connector. Select
the spectrum analyzer position on the DISPLAY column. Place the FUNCTION switch in the monitor position.
Select the desired width of sweep by the Dispr/Sweep control. The center frequency is selected from the
memory or entered directly from the keyboard, it is displayed at the top-right of the CRT. The following is an
example of locating the frequency of an incoming signal with the spectrum analyzer.
a.
Connect antenna to RF IN/OUT connector.
b.
Set FUNCTION switch to Mon. and DISPLAY to Spect. Analyzer.
c.
Select center frequency from memory table or enter directly from keyboard.
d.
Adjust Disp/Sweep control for desired spectrum span.
e.
Adjust Step attenuator if required to reduce sensitivity.
f.
g.
To determine whether a given displayed signal is valid or being internally generated, flip the
lmage/Dplx switch to the opposite position. If signal moves in frequency or disappears, it
then/represents an internally generated spurious response or received image.
Use the RF Scan control to move desired signal to center of the screen. If the signal is located to the
right of screen center line, move the RF Scan control clockwise into one of five positive stepping
modes. If the signal is to the left of screen center line, turn the RF Scan control counter clockwise to
one of five negative stepping modes.
h.
Adjust Dispr/sweep control fully counterclockwise for 1 MHz spectrum span.
i.
Again use RF Scan to recenter signal on screen.
j.
Set DISPLAY to Gen/Mon Mtr.
k.
Now adjust the RF scan control to minimize any existing frequency error between the incoming signal
and the Monitor frequency.
~14
~5
Advertisement
Table of Contents
