Agilent 8491B DC to 18 GHz Coaxial Fixed Attenuator (Pre-Owned)

Key Features At A Glance

• Frequency coverage from DC to 26.5 GHz with APC-3.5 connectors; performs resonance-free to 34 GHz
• Thin-film tantalum nitride on sapphire substrate for precision performance across the full band
• Attenuation accuracy within ±1.0 dB across the specified range, varying by attenuation value
• Low SWR: 1.10 (DC to 8 GHz), 1.15 (8 to 12.4 GHz), 1.25 (12.4 to 26.5 GHz) on most values
• Available in 3, 6, 10, 20, 30, and 40 dB attenuation values
• Maximum input power 2 W average, 100 W peak at 20°C (derated to 1.3 W average at 55°C)
• Every unit tested on a precision analyzer with actual values stamped on the attenuator body at DC, 4, 8, 12, 18, and 26.5 GHz

The Agilent 8493C is a precision coaxial fixed attenuator covering DC to 26.5 GHz with APC-3.5 connectors. It is part of a broader family that includes the 8491A/B (Type-N, to 12.4 or 18 GHz) and 8493A/B (SMA, to 12.4 or 18 GHz). The 8493C is constructed using thin-film tantalum nitride deposited on a sapphire substrate, which is the design choice that enables its precision performance across the full specified band and resonance-free operation up to 34 GHz — the top frequency limit of the APC-3.5 connector itself.

The 8493C is used as a precision attenuation element wherever signal levels need controlled reduction at microwave frequencies. Documented applications include extending the range of sensitive power meters for higher-power measurements, padding poorly matched devices to improve overall system SWR, serving as a calibration standard in attenuation and RF substitution measurements, and reducing power levels delivered to sensitive components and instrumentation. The combination of low SWR, flat frequency response, and broad DC-to-26.5 GHz coverage makes the same unit suitable for both bench work and integration into measurement systems.

Brand Heritage

Agilent Technologies was spun off from Hewlett-Packard in 1999, taking the test & measurement and chemical analysis businesses with it. In 2014 the electronic measurement portion of Agilent was further divided, with the test & measurement product lines transferring to the newly formed Keysight Technologies; Agilent retained the life sciences and chemical analysis businesses. Instruments and accessories carrying the Agilent brand from that era are part of the same engineering lineage now continued under Keysight.

Compare Other Models in This Series

The 8491/8493 series spans three connector and frequency tiers from a single family of thin-film resistive-card coaxial attenuators. The 8491A/B uses Type-N connectors and covers DC to 12.4 GHz (8491A) or DC to 18 GHz (8491B), with attenuation values from 3 dB through 60 dB. The 8493A/B uses SMA connectors with the same frequency split and value range from 3 dB through 30 dB. The 8493C uses APC-3.5 connectors and extends coverage to 26.5 GHz, with attenuation values from 3 dB through 40 dB.

Across the family, the design principle is the same — a film-on-card resistive element backed by the connector type and material chosen for the band. The 8493C uses tantalum nitride on sapphire for its precision performance at microwave frequencies, while the 8491A/B and 8493A/B use the family's standard film construction matched to their respective Type-N and SMA connector systems.

Each model in the family is listed as its own product page with condition-matched pricing. Selecting the pre-owned 8493C versus a pre-owned 8491A or 8493A is a connector and frequency-coverage decision driven by the application, not a tier-up or tier-down within a single product line.

Within the family, the 8493C is the model to specify when the application requires APC-3.5 connectors and frequency coverage above 18 GHz. Its tantalum-nitride-on-sapphire construction is the specific design element that distinguishes it from the 8491 and 8493A/B units and that enables its specified performance through 26.5 GHz and its resonance-free behavior to 34 GHz.

The family differences fall along three axes printed in the datasheet: connector type (Type-N on 8491A/B, SMA on 8493A/B, APC-3.5 on 8493C), upper frequency limit (12.4 GHz on the A suffix, 18 GHz on the B suffix, 26.5 GHz on the C), and available attenuation values (8491A/B offers 3 through 60 dB; 8493A/B offers 3 through 30 dB; 8493C offers 3 through 40 dB). Maximum SWR also tightens as the model moves to higher frequencies and the APC-3.5 connector — the 8493C is specified at 1.10 from DC to 8 GHz versus 1.25 on the 8491A/8493A and 8491B/8493B Type-N and SMA variants over the same band.

The comparison table below lays out connector type, frequency coverage, available attenuation values, and SWR by band for each model in the family. Use it to match the model to the specific connector environment and upper frequency required by the measurement.

Model	Frequency Range	Connector Type	Attenuation Values
8491B	dc to 18 GHz	Type-N	3, 6, 10, 20, 30, 40, 50, 60 dB
8491A	dc to 12.4 GHz	Type-N	3, 6, 10, 20, 30, 40, 50, 60 dB
8493A	dc to 12.4 GHz	SMA	3, 6, 10, 20, 30 dB
8493B	dc to 18 GHz	SMA	3, 6, 10, 20, 30 dB

Additional differences in specifications beyond the few shown above are not listed here — see each model's full specifications below.

Product Core & Specifications

Specification	8491A / 8493A	8491B / 8493B	8493C
Frequency Range	dc to 12.4 GHz	dc to 18 GHz	dc to 26.5 GHz
Impedance	50 Ω	50 Ω	50 Ω
Connectors (8491x)	Type-N	Type-N	—
Connectors (8493x)	SMA	SMA	APC-3.5
Temperature, non-operating	−55°C to +85°C
Temperature, operating	0°C to +55°C
EMC	Radiated interference within MIL STD 461 method RE02, VDE 0871 EN55011, FCC part 18
Temperature stability	0.0001 dB/dB/°C	0.0001 dB/dB/°C	0.0002 dB/dB/°C
Maximum input power	2 W avg., 100 W peak (at 20°C, derated to 1.3 W avg. at 55°C)
Power sensitivity	0.001 dB/dB/W	0.001 dB/W

Attenuation Accuracy

Attenuation	8491A/93A (dc to 12.4 GHz)	8491B/93B (dc to 12.4 GHz)	8491B/93B (12.4 to 18 GHz)	8493C (dc to 18 GHz)	8493C (18 to 26.5 GHz)
3 dB	±0.3 dB	±0.3 dB	±0.5 dB	±0.5 dB	±1.0 dB
6 dB	±0.3 dB	±0.3 dB	±0.4 dB	±0.3 dB	±0.6 dB
10 dB	±0.5 dB	±0.6 dB	±0.6 dB	±0.3 dB	±0.5 dB
20 dB	±0.5 dB	±0.6 dB	±1.0 dB	±0.5 dB	±0.6 dB
30 dB	±1.0 dB	±1.0 dB	±1.0 dB	±0.7 dB	±1.0 dB
40 dB (8491A/B only; 8493C)	±1.5 dB	±1.5 dB	±1.5 dB	±1.0 dB	±1.3 dB
50 dB (8491A/B only)	±1.5 dB	±1.5 dB	±1.5 dB	N/A	N/A
60 dB (8491A/B only)	±2.0 dB	±2.0 dB	±2.0 dB	N/A	N/A

SWR

Attenuation	8491A/8493A & 8491B/8493B (dc to 8 GHz)	8491A/8493A & 8491B/8493B (8 to 12.4 GHz)	8491B/8493B (12.4 to 18 GHz)	8493C (dc to 8 GHz)	8493C (8 to 12.4 GHz)	8493C (12.4 to 26.5 GHz)
3 dB	1.25	1.35	1.5	1.10	1.15	1.25
6 dB	1.2	1.3	1.5	1.10	1.15	1.27
10 dB	1.2	1.3	1.5	1.10	1.15	1.25
20 dB	1.2	1.3	1.5	1.10	1.15	1.25
30 dB	1.2	1.3	1.5	1.10	1.15	1.25
40 dB (8491A/B only; 8491B only @12.4-18; 8493C)	1.2	1.3	1.5	1.10	1.15	1.25
50 dB (8491A/B only)	1.2	1.3	1.5	N/A	N/A	N/A
60 dB (8491A/B only)	1.2	1.3	1.5	N/A	N/A	N/A

Dimensions & Weight

Model	Dimensions (mm)	Dimensions (in.)	Net Weight	Shipping Weight

Important: The 8493C performs resonance-free to 34 GHz, the upper frequency limit of the APC-3.5 connector itself; however, attenuation accuracy and SWR are warranted only through 26.5 GHz.Important: To order, basic model number and option (specifies attenuation value) must be specified. Each base model is sold with a selected attenuation value option (e.g., -003, -006, -010, -020, -030, -040, -050, -060).Important: Option 849xx-UK6 calibration data is not available with the 11581A, 11582A, or 11583C attenuator sets (these sets include their own calibration report).Important: Maximum input power 2 W avg., 100 W peak at 20°C; derated to 1.3 W avg. at 55°C. Do not exceed.Important: The 8493C is not specified above 26.5 GHz, but performs resonance-free to 34 GHz with only a small loss in performance (supplemental, non-warranted).Recommended pairing: the 11583C calibrated attenuator set bundles 3, 6, 10, and 20 dB 8493C units with a traceable calibration report and walnut storage case for lab and standards-room use.

About this used unit

• Warranty included
• Functional verification included
• Note that unnecessary accessories may not be included (contact Test Architect to confirm).

Please review the Manufacturer's Data Sheet to verify published specifications. Feedback on this webpage is always welcome — please reach out to your Test Architect at any time for questions or concerns. Thank you, we truly appreciate you being our customer.