Keysight 478A Coaxial Thermistor Mount
The Keysight 478A Coaxial Thermistor Mount (formerly Agilent Technologies) is designed for use with the Keysight Model 431 and 432 Power Meters to measure microwave power from 1 μW to 10 mW. Design of the mount minimizes adverse effects from enviromental temperature changes during measurement. For increased measurement accuracy, Effective Efficiency and Calibration Factor are measured for each mount, and at selected frequencies across the operating range; the results are marked on the label of the instrument.
The 478A can be used over the 10-HMz to 10-GHz frequeny range. Throughout the range, the mount terminates the coaxial input in a 50 ohm impedance, and has a SWR of not more than 1.75 without external tuning. Keysight 478A Coaxial Thermistor Mount instruments were previously manufactured by Agilent Technologies.
Output Connector
| Frequency Range | 10 MHz to 10 GHz | |
| Mount Calibration | Calibration Factor and Effective Efficiency furnished at six frequencies between 10 MHz and 10 GHz |
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| Impedance | 50 ohms | |
| Maximum Reflection Coefficient | 10 to 25 MHz | 0.273 (1.75 SWR, 11.3 dB return loss) |
| 25 MHz to 7 GHz | 0.13 (1.3 SWR, 17.7 dB return loss) | |
| 7 to 10 GHz | 0.2 (1.5 SWR, 14 dB return loss) | |
| Operating Resistance | 200 ohms | |
| Power Range | 1 μW to 10 mW | |
| Maximum Peak Power | 200W | |
| Maximum Average Power | 30 mW | |
| Maximum Energy per Puls | 10W • μs for a PRF ≥1HHz 5 W • μs for a PRF kHz |
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| Elements | Field-replaceable, thermally balanced thermistor assembly Thermistor assembly field adjustable so that full "zero-set" capability can be restored in the event inadvertent overload (mount calibration no longer valid) |
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| RF Connector | Type -N male, compatible with female connectors whose dimensions conform to MIL-C- 71 or MIL-C-39012. Brass connector. | |
| Mates with 431 and 432 cables. | ||
| Weight | net, 5 0z (140 g) Shipping, 1lb (450 g) | |
- High accuracy even in routine power measurements
- Temperature compensated for low drift
- Measures microwave power as low as one microwatt
- Shows calibration factor and effective efficiency at 12 frequencies
- Frequency Range: 10 MHz to 10 GHz
- Maximum SWR: 10 MHz to 25 MHz 1.75; 25 MHz to 7GHz 1.30; 7 GHz to 10 GHz 1.50
- Available options: 478A-H75 and 478A-H76 for frequency range 1 MHz to 1 GHz (Max. SWR 1.3, 1.05 at 50 MHz). 478A-H76 provides standard lab calibration at 50 MHz