Keysight 8478B – Coaxial Thermistor Mount (10 MHz to 18 GHz)

• High accuracy even in routine power measurements
• Designed to measure microwave power from 1μW to 10mW
• Frequency Range: 10 MHz to 18 GHz
• Type N (male) connector is standard
• For APC-7 connector, please select option 8478B-011

The Keysight Model 8478B Coaxial Thermistor Mount is designed to measure microwave power from 1μW to 10mW. The design of the mount minimizes adverse effects from environmental temperature changes during measurement. For increased measurement accuracy, Effective Efficiency and Calibration Factor are measured for each mount at selected frequencies across the operating range; the results are marked on the label of the instrument.

The Model 8478B can be used over the 10MHz to 18GHz frequency range. Throughout the range, the mount terminates the coaxial input in a 50-ohm impedance and has an SWR of not more than 1.75 without external tuning.

Each mount contains two series pairs of thermistors, which are matched to cancel the effects of drift with ambient temperature change. Thermal stability is accomplished by mounting the leads of all four thermistors on a common thermal conductor to ensure a common thermal environment. This conductor is thermally insulated from the main body of the mount so the thermal noise or shocks applied externally to the mount, such as those from handling the mount manually, cannot significantly penetrate to disturb the thermistor. This thermal immunity enables the thermistors to be used in the measurement of microwave power down to the microwatt region.

Maximum SWR:

•  10 MHz to 30 MHz: 1.75
•  30 MHz to 100 MHz: 1.35
•  100 MHz to 1 GHz: 1.10
•  1 GHz to 12.4 GHz: 1.35
•  12.4 GHz to 18 GHz: 1.60

Several options available

Keysight offers several options for the 8478B, including alternative connectors, calibration, and more. These options can be ordered from the accessories section of this page.

•  8478B-011 – APC-7 connector
•  8478B-H43 – Factory selected for best SWR from the batch. Std lab cal every 1 GHz to 18 GHz
•  8478B-H27 – Standards lab cal at 9MHz
•  8478B-H48 – Improved VSWR equal to 1.2:1 from 1 to 12GHz; 1.34:1 from 12 to 18GHz
•  8478B-H86 – Selected for best available VSWR, std lab cal at 26 frequencies
•  8478B-H84 – Std lab cal at specified frequencies
•  8478B-H01 – VSWR at or less than 1.05 at 50MHz