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General Information
Testing
Testing
Since the Model 478A Option H83 units are specified only up to
1000 MHz with Effective Efficiency and Calibration Factor varying
very little over the operating Frequency range, the following checks (made with the 478A
Option H83 connected to an operating 432A),
will generally ensure that the 478A Option H83 is operating properly:
1. Check SWR / Return Loss from 1 MHz to 1 GHz using a swept frequency network
analyzer or equivalent. A quick fixed frequency check at 1 MHz only will ensure that
blocking capacitor C2 is intact. Verify the following specifications in
2. CAL FACTOR: Carefully zero and set the 432A range switch to the
1 mW range on the 478A Option H83. Connect the 478A Option H83 to a precision 1
mW / 50 MHz power reference such as the 435A/B or 436A power meters or the 435A
Option K05 dual power reference. With the CAL FACTOR switch set to 100%, the 432A
should read between 0.95 and 1.02 mW (includes allowance for meter and power
reference errors).
Table 3
Typical VSWR Characteristics
Parameter
Max Return Loss / SWR
* Except at 50 MHz
6
Specification
Condition
17.7 dB / ≤ 1.3
1 MHz to 5 MHz
26.4 dB / ≤ 1.1
*5 MHz to 100 MHz
32.0 dB / ≤ 1.05
50 MHz
20.8 dB / ≤ 1.2
100 MHz to 1 GHz
Thermistor Mount Manual Modifications
478A Option H83
Table
3.
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