When building an amateur radio station, it’s good to have the skills and abilities to test your coax and antenna to determine whether they are functioning as expected... In this video, while working on station repairs, I calibrate the nanoVNA to examine my 80 meter NVIS dipole antenna at it's feedpoint while mounted at 35'. Some unexpected discoveries are made!
Subjects: Using the nanoVNA to measure antenna feedpoint SWR, impedance, and resonance. Testing coax cable for loss using the return loss method. Does antenna height effect antenna impedance?
The video wound up running on in time so I was not able to answer all the questions I had originally set out to investigate, so I will have to continue this experiment in a future video.
0:10 - Welcome to my Amateur Radio hobby workbench.
0:45 - Topics for today's video.
1:12 - A surprise package in the mail!
2:50 - DG0SA 1:1 current balun failure.
4:04 - What was I thinking when I built my NVIS station?
4:48 - Theoretical dipole antenna feedpoint impedance as a function of height above ground.
5:43 - Planning to match the feedpoint impedance of the balanced dipole antenna to the 50 ohm characteristic impedance of unbalanced feedline.
7:06 - Using the nanoVNA to analyze the mounted antenna (35' up in the air) - The "reference plane".
9:53 - Setting up the nanoVNA H4. Calibration for testing the coax cable feed line loss. (This assumes you know the basic calibration steps).
11:14 - Using the "return loss method" of measuring coax cable feed line loss.
12:14 - First reading with end of coax open.
12:21 - The "return loss method" - formula for calculating the feed line loss.
12:55 - Installing the short, taking the second measurement with the nanoVNA.
13:34 - Doing the math and discussing the result.
15:00 - Why keep records of station parameters?
16:13 - Calibrating the nanoVNA to analyze the antenna.
17:17 - Verifying the calibration.
19:04 - Questions I would like to answer.
19:35 - The dipole antenna being used for this test.
19:59 - Initial readings using the nanoVNA.
20:42 - Lowest SWR and antenna resonance.
20:55 - What is resonance? How to find the antenna's resonant frequency.
23:08 - Does "resonance" mean that the SWR of the antenna is 1:1?
23:28 - Dipole antenna feedpoint impedance vs antenna height. Theory vs actual readings.
24:36 - How to tell if your dipole antenna is too long or too short using nanoVNA readings? (Mistake corrected!)
28:03 - Unexpected result for the measured antenna feedpoint impedance and what will the measured impedance be when the antenna is lowered a bit?
28:49 - Another unexpected result after lowering the antenna!
30:18 - The value of taking real readings at your location rather than relying on theory to assume antenna behaviour.
31:03 - More questions for a future video...
31:35 - Final thoughts and closing! 73
VE6WGM (VE6WO)
16 фев 2024
