What is a connector saver?

A connector saver (also called a port saver) is a barrel adapter installed on expensive test instrument ports (VNA, spectrum analyzer, signal generator) to absorb the mechanical wear of repeated cable connections. Instrument port repairs cost 500 to 2000 dollars and require factory service. A precision barrel adapter costs 20 to 100 dollars and can be replaced when worn. The connector saver adds 0.1 to 0.2 dB insertion loss and slightly degrades return loss, but this is acceptable when de-embedded during calibration. For precision measurements, the connector saver is included in the calibration plane. For 2.4 mm and 1.85 mm connectors (operating to 50 and 67 GHz), precision connector savers with guaranteed VSWR less than 1.05 are essential because these small connectors are particularly fragile and expensive to repair.

What is the performance impact?

A quality barrel connector adds minimal degradation. Insertion loss: 0.05 to 0.3 dB depending on frequency and connector type. SMA barrel at 6 GHz: approximately 0.1 dB. SMA barrel at 18 GHz: approximately 0.3 dB. N barrel at 6 GHz: approximately 0.05 dB. Return loss: greater than 20 dB for precision adapters, greater than 15 dB for standard grade. Phase repeatability: less than 1 degree for precision, less than 5 degrees for standard. The main concern is that each additional connector interface creates a potential source of reflection (VSWR bump), intermodulation (PIM in cellular systems), and mechanical failure. In cascaded systems, the cumulative effect of multiple adapters can be significant. Rule of thumb: minimize the number of adapters in any RF path, especially above 6 GHz.

What types are available?

Barrel connectors are available for every standard RF connector type. SMA female-female: most common, DC to 18 GHz (or 26.5 GHz for precision), 50 ohm. N female-female: DC to 11 GHz (18 GHz for precision N), 50 ohm, higher power handling than SMA. BNC female-female: DC to 4 GHz, 50 or 75 ohm, quick-connect bayonet. Type F female-female: DC to 1 GHz, 75 ohm, used in CATV and satellite. TNC female-female: DC to 11 GHz, 50 ohm, threaded BNC for vibration resistance. 2.92mm (K) female-female: DC to 40 GHz, 50 ohm, precision. 2.4mm female-female: DC to 50 GHz, 50 ohm, precision. 1.85mm (V) female-female: DC to 67 GHz, 50 ohm, ultra-precision. Gender changers (male-male) are also available for reverse configurations.

Interconnect

Barrel Connector

/bar-el kuh-nek-ter/ — In-Series Adapter

Female-female coaxial adapter joining same-type cables. IL: 0.05-0.3 dB. RL: >20 dB (precision). Types: SMA (DC-18 GHz), N (DC-11 GHz), BNC (DC-4 GHz), 2.92mm (DC-40 GHz), 2.4mm (DC-50 GHz), 1.85mm (DC-67 GHz). Used: cable extension, connector saver on instruments ($20-100 vs $500-2000 port repair), test bench reconfig. Minimize adapters above 6 GHz.

IL: 0.05-0.3 dB

RL: >20 dB

Z: 50/75Ω

Understanding Barrel Connectors

The barrel connector is the simplest RF component, yet one of the most frequently used on any test bench. Its primary role is joining two cables of the same type without changing impedance, gender, or connector series. The most critical application is as a connector saver: a sacrificial adapter installed on expensive instrument ports to absorb the mechanical wear of hundreds of cable connection cycles.

At frequencies below 6 GHz, a quality barrel adds negligible loss and reflection. Above 6 GHz, every connector interface matters: each barrel adds a small VSWR bump that can ripple through cascaded measurements. Precision-grade barrels with guaranteed VSWR less than 1.05:1 are essential for metrology-grade work at mmWave frequencies.

Barrel Connector Specifications

Insertion loss vs frequency:
IL ≈ IL₀ + k√f (skin effect)
SMA: IL₀=0.03, k=0.015 dB/√GHz
@6 GHz: 0.03+0.015×2.45 = 0.07 dB
@18 GHz: 0.03+0.015×4.24 = 0.09 dB

Return loss:
RL = −20log|Γ| dB
VSWR 1.05: RL = 32.3 dB
VSWR 1.10: RL = 26.4 dB
VSWR 1.20: RL = 20.8 dB

Connector saver economics:
Barrel: $20-100 (replaceable)
Port repair: $500-2000 (factory)

Barrel Connector Types

Type	Freq Max	IL @max	Impedance	Application
BNC F-F	4 GHz	0.2 dB	50/75Ω	Lab, video
SMA F-F	18 GHz	0.3 dB	50Ω	General RF
N F-F	11 GHz	0.15 dB	50Ω	High power
2.92mm F-F	40 GHz	0.3 dB	50Ω	mmWave test
1.85mm F-F	67 GHz	0.5 dB	50Ω	Precision

Common Questions

Frequently Asked Questions

Connector saver?

Barrel on instrument port absorbs wear. Instrument repair: $500-2000 + downtime. Barrel: $20-100, replaceable. Include in calibration plane to de-embed. Essential for 2.4mm/1.85mm (fragile, expensive). VSWR <1.05 for precision. Every lab should use them.

Performance impact?

IL: 0.05-0.3 dB (freq dependent, skin effect). RL: >20 dB precision, >15 dB standard. Phase: <1° precision, <5° standard. Each adapter = reflection source + potential PIM + failure point. Minimize adapters, especially above 6 GHz. Cascade effects add up.

Types?

Every standard connector: SMA, N, BNC, TNC, Type F, 2.92mm, 2.4mm, 1.85mm, 1.0mm. Female-female most common. Male-male (gender changers) also available. 50Ω (RF) and 75Ω (CATV/broadcast). Precision vs standard grade. Stainless steel or brass/gold.

Related Terms

← Barker Code Baseband →

RF Interconnects

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