Junkosha Inc.MWX8 SeriesMetrology Grade

Your VNA Calibration Lasts Until You Move the Cable.

Every time a standard test cable flexes, it introduces phase error. The 8 Series guarantees a maximum of ±4.5° at 50 GHz — through 40,000 flex cycles. When the cable stops mattering, the measurement can begin. Available in Israel through Koto Electronics.

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50 Ω — All VariantsNMD Ruggedized Port ConnectorAuthorized Israeli Rep.

Junkosha 8 Series VNA Test Cable Assembly

±4.5°

Max Phase Stability at 50 GHz

±0.08 dB

Max Amplitude Stability at 50 GHz

40,000+

Flex Cycle Durability

50 GHz

Maximum Frequency (MWX851)

The calibration problem nobody talks about

The Moment You Touch the Cable, the Calibration is Conditional

VNA calibration removes systematic errors — but only for the state of the cable at the time of calibration. Every subsequent flex changes that state. If the cable contributes phase error that the VNA can't distinguish from the device, you are measuring the cable.

Calibration Walking

You calibrate the VNA, then flex the cable 30 times reaching different DUT orientations. Each flex shifts the cable's phase — the calibration correction terms are now wrong. The S-parameter you're recording is partially the calibration drift.

Phase Drift You Can't See

Standard test cables specify phase in a static position — which is not how you use them. The number that matters is phase stability in flexure. Without that spec, you have no way to bound the error your cable introduces during a real measurement session.

Port Connector Wear

The VNA port connector is disconnected and reconnected on every DUT. Standard connectors wear, lose repeatability, and eventually introduce connection uncertainty that is impossible to separate from measurement noise. A ruggedized port-side interface changes the failure mode.

The solution

A Cable That Is Invisible to the Measurement

The 8 Series is designed around a single principle: a VNA test cable should contribute nothing to the measurement result. Phase stability, amplitude stability, and mechanical durability are all specified for flexure — not static position.

✓
±4.5° Max Phase Stability at 50 GHz — In Flexure
Not typical. Not static. The maximum phase change during a 180° bend on a 57 mm mandrel is ±4.5° at 50 GHz. The measured traces (before, during, and after the bend) hold well within that envelope — you have a hard upper bound on your cable-induced phase error.
✓
±0.08 dB Amplitude Stability — Through the Same Flex
Insertion loss variation during flexure is bounded at ±0.08 dB at 50 GHz for the 635 mm assembly. For amplitude-sensitive measurements like filter insertion loss or gain compression, this gives you a defined, documentable uncertainty floor for the cable contribution.
✓
40,000+ Flex Cycles — Tested, Not Estimated
Junkosha's durability testing exceeds 40,000 tick-tock cycles — a full 180° bend and return — with no degradation in performance. That represents years of daily laboratory use. The cable outlasts the measurement program, not the other way around.
✓
180° Bend on 57 mm Mandrel — No Spring-Back
The cable bends fully and returns without spring-back. This means it doesn't fight you when reaching an awkward DUT position, and doesn't exert residual tension on the VNA port after you stop handling it.
✓
NMD Ruggedized Connector — Port-Side Reliability
The ruggedized NMD connector on the VNA port side is designed for repeated connection cycles without degrading repeatability. Where a standard connector's mating performance drifts over hundreds of insertions, the NMD interface maintains consistent electrical contact.

Phase Stability — MWX851 at 50 GHz

Typical measured result: Before / During / After 180° flex on 114 mm mandrel

+4.5°

−4.5°

0 → 50 GHz

Before, during, and after the flex test, the cable's phase trace holds well within the ±4.5° specification limit. The cable's contribution to your measurement error is bounded and documentable.

Applications

VNA Port Extension
S-parameter measurements where cable movement is unavoidable
Component Characterization
Filter, amplifier, and passive component measurement
Antenna & Feed Testing
Swept-frequency measurements requiring cable flexure
Calibration Verification
Stable baseline reference for calibration audits

8 Series — VNA Test Assemblies

Two Variants. One Standard.

Both variants share the same 14.2 mm OD cable, NMD port-side connector, and 57 mm minimum bend radius. Choose by maximum operating frequency.

MWX82126.5 GHz

821 — 26.5 GHz VNA

26.5 GHz — VSWR 1.29:1, ±3.9° max phase stability in flexure

635 mm (25")

Phase Stability±3.9° @ 26.5 GHz

Amplitude Stability±0.08 dB @ 26.5 GHz

Insertion Loss (typ.)1.75 dB

Insertion Loss (max)2.1 dB

965 mm (38")

Phase Stability±7.1° @ 26.5 GHz

Amplitude Stability±0.15 dB @ 26.5 GHz

Insertion Loss (typ.)2.45 dB

Insertion Loss (max)2.8 dB

Outer Diameter14.2 mm

Cable Mass240 g/m

VSWR (typ.)1.29:1

Velocity of Prop.79%

Min. Bend Radius57 mm (2.25")

Temp. Range23 ±5 °C

Connectors: NMD 3.5 mm (f/m), 3.5 mm (f) Straight

MWX85150.0 GHz

851 — 50.0 GHz mmWave VNA

50 GHz mmWave — ±4.5° max phase stability, >40,000 flex cycles

635 mm (25")

Phase Stability±4.5° @ 50.0 GHz

Amplitude Stability±0.08 dB @ 50.0 GHz

Insertion Loss (typ.)3.6 dB

Insertion Loss (max)4.5 dB

965 mm (38")

Phase Stability±9.0° @ 50.0 GHz

Amplitude Stability±0.15 dB @ 50.0 GHz

Insertion Loss (typ.)5.1 dB

Insertion Loss (max)6.2 dB

Outer Diameter14.2 mm

Cable Mass200 g/m

VSWR (typ.)1.43:1

Velocity of Prop.79%

Min. Bend Radius57 mm (2.25")

Temp. Range23 ±5 °C

Connectors: NMD 2.4 mm (f/m), 2.4 mm (f) Straight

Full Specification Comparison

All stability values measured in flexure. 50 Ω impedance. Operating temperature 23 ±5 °C.

Model	Length	Max Freq.	Phase Stability	Amplitude Stability	Ins. Loss (typ.)	Ins. Loss (max)	VSWR	OD	Mass
MWX821	635 mm (25")	26.5 GHz	±3.9°	±0.08 dB	1.75 dB	2.1 dB	1.29:1	14.2 mm	240 g/m
MWX821	965 mm (38")	26.5 GHz	±7.1°	±0.15 dB	2.45 dB	2.8 dB	1.29:1	14.2 mm	240 g/m
MWX851	635 mm (25")	50.0 GHz	±4.5°	±0.08 dB	3.6 dB	4.5 dB	1.43:1	14.2 mm	200 g/m
MWX851	965 mm (38")	50.0 GHz	±9.0°	±0.15 dB	5.1 dB	6.2 dB	1.43:1	14.2 mm	200 g/m

Shielding effectiveness >90 dB to 18 GHz. Velocity of propagation 79%.

Connector Options

NMD (ruggedized) connectors are used on the VNA port side. Standard precision connectors on the DUT side.

MWX821 — 26.5 GHz Connectors

NMD ruggedized and standard 3.5 mm options

DFDNMD 3.5 mm (f) — ruggedized, for VNA port side
DMDNMD 3.5 mm (m) — ruggedized, for VNA port side
DFS3.5 mm (f) Straight — standard, DUT side

MWX851 — 50.0 GHz Connectors

NMD ruggedized and standard 2.4 mm options

LFDNMD 2.4 mm (f) — ruggedized, for VNA port side
LMDNMD 2.4 mm (m) — ruggedized, for VNA port side
LFS2.4 mm (f) Straight — standard, DUT side

Order format: Cable type · Length (mm) · Connector I code · Connector II code · Armor. Example: MWX821-00635-DFDDMD/B = 821 cable, 635 mm, NMD 3.5mm (f) + NMD 3.5mm (m), armored.

Frequently Asked Questions

What is 'phase stability in flexure' and why does it matter for VNA measurements?

Phase stability in flexure is how much the cable's phase response changes when you bend or move it during a measurement. If you calibrated the VNA with the cable in one position and then flex it to reach the DUT, any phase shift in the cable appears as measurement error — not device behavior. The 8 Series guarantees a maximum of ±4.5° at 50 GHz regardless of how you flex the cable.

What is an NMD connector and why is it specified for the port side?

NMD (Navy Micro D) is a ruggedized connector designed for reliable, repeatable connections at the VNA port — where the cable is connected and disconnected most frequently. The ruggedized body protects the precision interface from mechanical wear. On the DUT side, standard 3.5 mm (f) or 2.4 mm (f) straight connectors are used to mate with test fixtures and devices.

Why does phase stability worsen with the 965 mm length?

A longer cable creates a longer mechanical lever — the same angular movement at the midpoint produces a greater change in the cable's electrical length. For the most stable measurements, specify the 635 mm length wherever the test setup allows. Use 965 mm when the VNA-to-DUT distance requires it.

The spec says ±4.5° at 50 GHz. Is that typical or maximum?

That is the maximum — a guaranteed limit, not a typical value. The typical performance (as shown in the flexure graph for Cable Type 851) is significantly better, with the phase trace remaining well within the ±4.5° envelope before, during, and after the 180° bend test. The spec gives you a hard ceiling, not an average.

How many flex cycles can the cable withstand?

More than 40,000 tick-tock cycles during Junkosha's testing, where the cable is bent 180° on a 2.25" (57 mm) radius mandrel and returned to straight. That exceeds the working life of most lab instruments and represents many years of daily use in a typical measurement environment.

Which variant should I specify — MWX821 or MWX851?

Match the variant to the maximum frequency your VNA and measurements require. MWX821 covers up to 26.5 GHz with 3.5 mm connectors (compatible with standard SMA-level VNA ports). MWX851 covers up to 50 GHz with 2.4 mm connectors for mmWave VNAs. Both share the same 14.2 mm cable OD and NMD port-side interface.

The MWX Series Family

The full MWX product family covers RF and microwave cable assemblies for every test and measurement application.

0 Series

26.5 – 145 GHz

1 Series

Wide Temp. / High Durability

2 Series

Flexible / Low Repulsion

3 Series

Temp. Phase Stability

Stop Working Around Cable Uncertainty

When the cable's phase error is bounded to ±4.5° and its durability is proven to 40,000 cycles, it stops being a variable in your measurement. Specify it once. Then focus on the device.

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