Wavetek 2001 Instruction Manual page 34

Model 2001
MAINTENANCE
rtlO MHz, and on band 2 and 3 520 MHz. Again, accuracy
on band 2 and 3 i s affected by the OUTPUT vernier control.
START/STOP MODE: Return to BAND 1 and set the
MODE to S/S (Start/Stop). Set START to -1 0 MHz and
STOP to 510 MHz. A pattern similar to Figure 5-5 should
be present on the scope display. Reduce STOP control
until the 500 MHz marker just disappears from the right
side of i t s scope display; read error of the STOP frequency
indicator (red), repeat a t each 50 MHz interval.
Return STOP dial to 510 MHz and adjust START control
until the zero lock-in point just disappear from the left
side of the scope display; read error of the START frequency
indicator (green), repeat at each 50 MHz interval. Allowable
error is the same a s band 1 in the a f mode, k10 MHz.
Recheck for bands 2 and 3, vary OUTPUT vernier at each
50 MHz check point. Allowable error is 2% of indicated
frequency.
5.3.7 C W MODE CHECK
Turn MODE switch to CW. This position removes the re-
turn trace blanking and the sweep width drive from the
oscillator. The output frequency is controlled by the
CENTER FREQ control and the dial accuracy will be the
same a s previously checked at the a f mode. The detected
pattern on the scope will be a negative voltage equal to that
produced in the S/S and a f mode with the absence of the
zero level return trace.
5.3.8 SPURIOUS SIGNAL CHECK
Checking for spurious signal content is not normally requir-
ed for periodic calibration, only for initial incoming inspec-
tion. The only practical way to measure the spurious signal
content is with a high quality spectrum analyzer covering
the frequency range of 10 MHz to 3 GHz. The spurious
check
is
made in accordance to the instructions furnished
with the particular spectrum analyzer.
The main spurious signals on all three bands is the second
and third harmonic of the output signal and should be
more than 26dB below the main output signal from 10 to
500 MHz on band 1 and 26dB below the output signal from
500 to 1400 MHz on bands 2 and 3. Harmonic content is
not specified below 10 MHz on band 1 and an increase of
the second harmonic output to approximately 22dB below
the output in the 450 to 500 MHz area of band 2 is normal.
In
addition to
the
harmonically related spurious signals,
band 1 will have non-harmonic spurious signals due to the
hetrodyne method of obtaining the sweep output signal.
These spurious signals are typically 40 to 50dB below the
output from 10 to 400 MHz and increase to no more than
26dB below the output in the 400 to 500 MHz area.
5.3.9 RF OUTPUT FLATNESS (amplitude variations vs.
frequency)
Flatness can be checked with a negative polarity RF detec-
tor or a power meter. The power meter method is to be
preferred since its own flatness is better than that of most
RF detectors. A 0.5dB detector flatness is typical of many
detectors over this frequency range. However, the power
meter has two limitations not present in the RF detector.
First, slow response time and second, not useable below
20 MHz. The first limitation can be overcome by making
the flatness measurements in the C W mode, the second by
making flatness measurements with a detector in the low
frequency area.
To measure flatness, set the MODE switch to CW, OUTPUT
control to +lWBm, and connect the power meter to the
RF output connector. Tune the entire frequency range
from 20 to 1400 MHz and note the frequency where maxi-
mum output was obtained. With the OUTPUT VERNIER
control
set
the output at that frequency to exactly +lWBm.
Again tune the entire band and note the minimum output
reading. A minimum output of 8.5dBm or more is required
to meet the flatness specifications of k0.75dB.
5.3.10 RF OUTPUT LEVEL
The MAX R F output level is set to produce exactly
+
1 WBm
at 300 MHz. This produces the minimum error over the
greatest frequency range and can be checked by using the
power meter while operating the instrument in the C W
mode.
5.3.11 ATTENUATORS
20dB Vernier: The accuracy of the 20dB vernier can be
checked using the power meter while operating the instru-
ment in the C W mode. The vernier dial
is
calibrated at 300
MHz. Dial accuracy is *0.5dB to 500 MHz, L l d B to 1000
MHz. and k2dB to 1400 MHz. This error is contributed
by the vernier and does not include the basic flatness error
at +lWBm.
70dB Attenuator: The accuracy of the step attenuator can
be measured by using a suitable Attenuation Test Set or by
directly substituting precision RF attenuator pads for each
10dB step of the attenuator. The difference between the
two outputs represents the attenuator error. An
RF
Model 2001
± 10 MHz, and on band 2 and 3 ±20 MHz. Again, accuracy
on band 2 and 3 is affected by the OUTPUT vernier control.
START/STOP MODE: Return to BAND 1 and set the
MODE to SIS (Start/Stop). Set START to -10 MHz and
STOP to 510 MHz. A pattern similar to Figure 5-5 should
be present on the scope display. Reduce STOP control
until the 500 MHz marker just disappears from the right
side of its scope display; read error of the STOP frequency
indicator (red), repeat at each 50 MHz interval.
Return STOP dial to 510 MHz and adjust START control
until the zero lock:-in point just disappear from the left
side of the scope display; read error of the START frequency
indicator (green), repeat at each 50 MHz interval. Allowable
error is the same as band 1 in the
0.
f mode, ± 10 MHz.
Recheck for bands 2 and 3, vary OUTPUT vernier at each
50 MHz check point. Allowable error is 2% of indicated
frequency.
5.3.7 CW MODE CHECK
Turn MODE switch to CWo This position removes the re-
turn trace blanking and the sweep width drive from the
oscillator. The output frequency is controlled by the
CENTER FREQ control and the dial accuracy will be the
same as previously checked at the
0.
f mode. The detected
pattern on the scope will be a negative voltage equal to that
produced in the SIS and
0.
f mode with the absence of the
zero level return trace.
5.3.8 SPURIOUS SIGNAL CHECK
Checking for spurious signal content is not normally requir-
ed for periodic calibration, only for initial incoming inspec-
tion. The only practical way to measure the spurious signal
content
is
with a high quality spectrum analyzer covering
the frequency range of 10 MHz to 3 GHz. The spurious
check is made in accordance to the instructions furnished
with the particular spectrum analyzer.
The main spurious signals on all three bands
is
the second
and third harmonic of the output signal and should be
more than 26dB below the main output signal from 10 to
500 MHz on band 1 and 26dB below the output signal from
500 to 1400 MHz on bands 2 and 3. Harmonic content is
not specified below 10 MHz on band 1 and an increase of
the second harmonic output to approximately 22dB below
the output in the 450 to 500 MHz area of band 2 is normal.
In
addition to
the
harmonically related spurious signals,
band 1 will have non-harmonic spurious signals due to the
MAINTENANCE
hetrodyne method of obtaining the sweep output signal.
These spurious signals are typically 40 to 50dB below the
output from 10 to 400 MHz and increase to no more than
26dB below the output in the 400 to 500 MHz area.
5.3.9 RF OUTPUT FLATNESS (amplitude variations vs.
frequency)
Flatness can be checked with a negative polarity Rf detec-
tor or a power meter. The power meter method is to be
preferred since its own flatness is better than that of most
RF detectors. A 0.5dB detector flatness is typical of many
detectors over th is frequency range. However, the power
meter has two limitations not present in the R F detector.
First, slow response time and second, not useable below
20 MHz. The first limitation can be overcome by making
the flatness measurements in the CW mode, the second by
making flatness measurements with a detector in the low
frequency area.
To measure flatness, set the MODE switch to CW, OUTPUT
control to +lOdBm, and connect the power meter to the
RF output connector. Tune the entire frequency range
from 20 to 1400 MHz and note the frequency where maxi-
mum output was obtained. With the OUTPUT VERNIER
control set the output at that frequency to exactly +1 OdBm.
Again tune the entire band and note the minimum output
reading. A minimum output of 8.5dBm or more is required
to meet the flatness specifications of ±0.75dB.
5.3.10 RF OUTPUT LEVEL
The MAX R F output level is set to produce exactly + 1 OdBm
at 300 MHz. This produces the minimum error over the
greatest frequency range and can be checked by using the
power meter while operating the instrument in the CW
mode.
5.3.11 ATTENUATORS
20dB Vernier: The accuracy of the 20dB vernier can be
checked using the power meter while operating the instru-
ment in the CW mode. The vernier dial is calibrated at 300
MHz. Dial accuracy is ±O.5dB to 500 MHz, ± 1dB to 1000
MHz, and ±2dB to 1400 MHz. This error is contributed
by the vernier and does not include the basic flatness error
at +lOdBm.
70dB Attenuator: The accuracy of the step attenuator can
be measured by using a suitable Attenuation Test Set or by
directly substituting precision RF attenuator pads for each
lOdB step of the attenuator. The difference between the
two outputs represents the attenuator error.
An RF
5-5