Keysight 478A Coaxial Thermistor Mount

HP/Agilent 478A Coaxial Thermistor Mount
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HP/Agilent 478A Coaxial Thermistor Mount HP/Agilent 478A Coaxial Thermistor Mount HP/Agilent 478A Coaxial Thermistor Mount
Keysight 478A
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The Keysight 478A Coaxial Thermistor Mount 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 Model 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.



  • 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



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
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
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adjustable so that full "zero-set" capability can be restored in the event inadvertent overload (mount calibration no longer valid)
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)