TODO-DIY-BNC-CAL-KIT.MD

TO-DO: Cheap DUTs to compare DIY BNC calibration vs SMA calibration kit

Goal: check whether the DIY BNC calibration kit gives practical amateur-level results close to a reference SMA calibration kit.

Test rules

• Use the same NanoVNA, sweep range, number of points, adapters, and settings
• Save screenshots for both calibrations
• Compare both traces and marker values
• Repeat each DUT connection at least 3 times

DUTs to test

• Independent 50 ohm load
  Check whether both calibrations show a similar match, return loss, and impedance

• Fixed attenuator (3 dB / 6 dB / 10 dB)
  Check S21 attenuation and overall flatness

• Short coax cable
  Measure with open and short at the far end, then compare Smith chart behavior

• BNC barrel / SMA-BNC adapter / through adapter
  Check insertion loss and mismatch

• Simple resistive DUTs (33 ohm / 75 ohm / 100 ohm)
  Check whether the measured mismatch and impedance make sense

• Cheap LC or SAW filter
  Compare passband, stopband, and general trace shape

• Optional real-world DUT
  Small antenna, matching network, or radio dummy load

Suggested test order

• 50 ohm load
• Fixed attenuator
• Short coax cable
• Adapters / barrel
• 33 ohm / 75 ohm / 100 ohm loads
• Filter
• Optional antenna-related DUT

Practical pass/fail criteria

• PASS: results are close to the SMA calibration kit across the intended frequency range

• PASS: repeated connections give similar results

• PASS: loads, attenuators, cables, and filters behave as expected

• WARNING: noticeable differences appear only near the upper frequency limit

• FAIL: results change too much after reconnecting the DUT

• FAIL: DUT behavior looks clearly wrong compared to the SMA calibration kit

• FAIL: the DIY kit only looks good when measuring its own standards