Published on 10/13/2026
A purchasing manager asks for "a test report" with every cable. The supplier sends a one-line certificate: "Tested OK." The engineer who receives the cables cannot tell whether OK meant a continuity beep or a full 18 GHz sweep, and has no data to compare when a cable misbehaves six months later.
A useful report is a short document that proves what was measured, how, against what limit, and on which cable. This guide describes what a good cable assembly test report contains, how to read a VSWR and insertion loss plot, and what to ask for when you place an order.
For the theory behind the three numbers see our article on insertion loss, return loss and VSWR, and for how to write the order see our RFQ checklist.
On This Page
| Section | Typical content | Why you want it |
|---|---|---|
| Identification | Part number, revision, serial number, date, operator | Traceability |
| Equipment | VNA model, calibration date, cal kit, test cables, adapters | Shows the measurement is credible |
| Setup | Frequency range, number of points, IF bandwidth, power level, calibration type | Lets you repeat the test |
| Continuity | Center and shield continuity, no short | Catches build faults |
| VSWR or return loss | Plot across the band with limit line, worst-case value and frequency | Core RF quality indicator |
| Insertion loss | Plot or values at specified frequencies vs limit | Confirms loss budget |
| Result | Pass or fail against stated limits | The decision record |
| Optional | Phase, length (TDR), DC resistance, high-pot | Specific applications |
VSWR and return loss are two views of the same measurement. Return loss in dB is minus twenty times the log of the reflection coefficient. VSWR is the ratio form. Lower VSWR and higher return loss are better.
| VSWR | Return loss (dB) | Reflected power |
|---|---|---|
| 1.05 | 32.3 | 0.1 percent |
| 1.10 | 26.4 | 0.2 percent |
| 1.20 | 20.8 | 0.8 percent |
| 1.30 | 17.7 | 1.7 percent |
| 1.50 | 14.0 | 4.0 percent |
| 2.00 | 9.5 | 11.1 percent |
Look at the worst point, not the average. A narrow spike at one frequency can be a connector or a kink. A slow rise with frequency is normal for most cable and connector combinations, which is why limits are often stated per frequency range, such as 1.20 to 6 GHz and 1.35 to 18 GHz.
Insertion loss is the signal lost through the cable and connectors, in dB, and it grows with frequency and length. A report should show it across the band or at the frequencies that matter to you. Check it against the cable datasheet: a 1 m RG316 assembly with good connectors should land near the cable's rated attenuation plus a small amount for the connectors, and a value far above that signals a problem.
Also confirm that the IF bandwidth and averaging are reasonable. A very wide IF bandwidth adds noise and can hide small ripple.
Step 01
State the limits
VSWR or return loss and insertion loss limits at named frequencies, so pass or fail has meaning.
Step 02
State the sweep range
For example 100 MHz to 18 GHz or to the highest frequency you use.
Step 03
Ask for the format
PDF with plots, or CSV or Touchstone (.s2p) files if you need the raw data.
Step 04
Ask for serial linkage
Each cable should have a serial number or label that matches its report.
Step 05
Decide on sampling
Every unit is best for critical links. Sample testing may suit simple, high volume jumpers.
At SigmaRF every assembly is VNA-swept for VSWR and insertion loss before shipment, 100 MHz to 40 GHz. Tell us the report format and limit lines you need when you request the quote so we can confirm them.
Loose or bad connectorPoor crimpKinked cableWrong connector typeDamaged pinExcess lossOpen or short
Weak reports
What should a cable assembly test report include?
Part and serial number, VNA and calibration details, frequency range, continuity result, VSWR or return loss plot with limits, insertion loss, and a pass or fail result.
What does 100 percent tested mean for a cable assembly?
Every unit is tested, not a sample. It should be stated with what was tested, such as VSWR and insertion loss across a stated range.
What is a good VSWR for a coax cable assembly?
Below 1.3:1 for typical assemblies to 6 GHz and below about 1.5:1 at higher frequencies, depending on connectors. The limit should match your application.
What is the relation between VSWR and return loss?
A VSWR of 1.5 equals 14 dB return loss. A VSWR of 1.2 equals 20.8 dB. Lower VSWR means higher return loss.
How is insertion loss tested on a cable?
With a VNA measuring S21 across the band after a calibration at the connector reference planes.
Do I get a certificate of conformance?
Ask when you place the order. Confirm the format and what it covers in the quote.
What file formats can test data come in?
PDF for plots, CSV for tables, and Touchstone (.s2p) for S-parameters that import into simulation tools.
Why do cables fail a VSWR test?
Common causes are a bad crimp or solder joint, damaged connector pin, kinked cable, wrong connector, or contamination.
A test report is only useful if it names the measurement, the limit, the equipment and the cable. Ask for the sweep range, the limit lines and the serial linkage when you order, and keep the data with the part.
SigmaRF sweeps every assembly on a VNA for VSWR and insertion loss before it ships, from 100 MHz to 40 GHz, at our India (Vadodara) volume facility and USA (Cleveland area) precision facility. Lead times can be as short as 2 days.
Need tested assemblies with data?
Tell us the limits and report format with your request.
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