What You Will Need

• NanoVNA with the supplied CH0-to-CH1 jumper cable
• The coax cable(s) you want to test
• A connector with the center pin shorted to the shield (for the SHORT calibration step — a PL-259 or BNC with the center pin soldered to the outer shell works perfectly)
• MFJ-261 50Ω dummy load (for the LOAD calibration step)

Step 1 — Set Your Frequency Range

Set a wide sweep that covers all the HF bands you use. Do this before calibrating — calibration is only valid for the range set when it was performed. Do not change the range after calibrating.

1. Go to STIMULUS → START → enter 1 → tap M (sets 1 MHz)
2. Go to STIMULUS → STOP → enter 30 → tap M (sets 30 MHz)

Step 2 — Calibrate

Attach your jumper cable to CH0 first, then calibrate. This zeros out the jumper so it doesn't affect your readings. Go to CAL → CALIBRATE and perform each step in order:

When complete: tap DONE → then CAL → SAVE → SAVE 0

Step 3 — Set the Display for Easy Reading

1. Go to DISPLAY → TRACE → TRACE 1 (S21)
2. Go to FORMAT → LOGMAG
3. Go to DISPLAY → SCALE → set SCALE/DIV to 1 dB
4. Set REFERENCE POSITION to the top line of the grid
5. Set REFERENCE VALUE to 0 dB

The top of the grid is now 0 dB. Each grid line down = 1 dB of loss. A good coax will show a flat line near the top of the screen.

Step 4 — Verify Your Setup is Working

1. Connect CH0 directly to CH1 using only the short supplied jumper — no coax under test yet
2. The trace should sit near the top of the screen, close to 0 dB
3. If it does — your calibration is good and you are ready to test ✓
4. If it shows large negative numbers (e.g. −20 dB or worse) — recalibrate from Step 2

Step 5 — Test Each Coax Cable

1. Connect one end of the coax to CH0
2. Connect the other end to CH1
3. Observe the trace and read the loss value

Step 6 — Use a Marker for Exact Readings

1. Go to MARKER → MARKER 1
2. Move the marker to any point on the trace
3. The exact dB value displays as a number on screen — no guesswork needed

What You Will Need

• USB-C cable (the same one used to charge the NanoVNA)
• A Windows, Mac, or Linux computer
• NanoVNA-Saver software (free — see Step 1)

Step 1 — Download and Install NanoVNA-Saver

• For Ubuntu-based Linux, the .appimage was available at one time and might return. Here's the alternative method using pipx:
  1. Check your version of pipx:
     
     pipx --version
  2. If you need to update pipx:
     
     pip install --upgrade pipx --break-system-packages
  3. Verify your version of pipx:
     
     pipx --version
  4. Make sure the pipx PATH is set:
     
     pipx ensurepath
  5. Close, then reopen your terminal:
     
     exit
  6. Install NanoVNA-Saver:
     
     pipx install git+https://github.com/NanoVNA-Saver/nanovna-saver
  7. Serial port permission (do this once):
     
     sudo usermod -aG dialout $USER
  8. Full logout and log back in:
     
     reboot
• [If Step 6 above fails, Mint 22.3 sometimes needs these dependencies first:]
  
  sudo apt install python3-pyqt5 python3-dev
• For Windows: go to github.com/NanoVNA-Saver/nanovna-saver/releases and download the .exe installer

Step 2 — Connect the NanoVNA

1. Power on your NanoVNA first
2. Connect the USB-C cable from the NanoVNA to your computer
3. Wait a few seconds for Linux Mint to recognize the device. Windows may install a driver automatically — give it a moment to complete

Step 3 — Connect in NanoVNA-Saver

1. Launch NanoVNA-Saver
2. In the left column, find the Serial port control dropdown
3. Click Rescan to find your device
4. Select the port that appears:
   • Linux: /dev/ttyUSB0 or similar
   • Windows: COM3 or similar
5. Click Connect to device
6. The software will begin pulling live data from the NanoVNA — you should see the traces appear on screen

Step 4 — Set Your Frequency Range in NanoVNA-Saver

1. In the Sweep settings panel on the left, enter your Start and Stop frequencies
2. Set the number of segments — more segments means more measurement points. For 1–30 MHz, 3 to 4 segments gives a good balance of speed and detail
3. Click Sweep to run a scan

Step 5 — Reading Coax Loss in NanoVNA-Saver

With your coax connected CH0 to CH1 as described in Section 1:

1. Look at the S21 panel in NanoVNA-Saver
2. Click the format dropdown and select Gain (dB) — this is the equivalent of LOGMAG on the device itself
3. Use the same loss reference table from Section 1, Step 5 to interpret your readings
4. The larger computer screen makes it much easier to spot a subtle downward slope in a lossy or water-damaged cable that can be hard to see on the small NanoVNA display

Step 6 — TDR: Locating a Fault in the Cable

NanoVNA-Saver includes a TDR (Time Domain Reflectometry) tab that can show you approximately where in a cable a fault is located — very useful for long buried runs or tower feedlines.

1. Click the TDR tab in NanoVNA-Saver
2. Enter your cable's velocity factor:

The TDR display will show a spike at the point of reflection. The distance on the horizontal axis tells you how far the fault is from your end of the cable in feet or meters.

Step 7 — Saving Your Results

1. Go to File → Save to save sweep data as a .s1p or .s2p Touchstone file for later comparison
2. To save a screenshot of the NanoVNA-Saver window, use your computer's built-in tool:
   • Windows: Win + Shift + S
   • Mac: Cmd + Shift + 4
   • Linux: use your desktop's screenshot tool or scrot
3. Name files descriptively — e.g. coax_tower_run_2026.png — so you can compare them over time