I recently built a 340 MHz dipole for test purposes. My NanoVNA-H4 was calibrated initially at the transmitter end of the coax cable. The first attachment shows the response of the antenna with transmission line from 200 MHz through 500 MHz. It was quite surprising to see the result. The transmission line is 15 feet of RG-58A/U coax.
The next step was to calibrate the NanoVNA-H4 at the antenna end of the transmission line. As you can see in the second attachment, the difference is quite dramatic.
I'd be interested in any comments. There is a 24 MHz difference between the various peaks and valleys in the first chart. It turns out that the transmission line is a half wavelength at 24 MHz after accounting for the velocity factor. It appears that frequencies that are multiples of 24 MHz come into play. I wonder if there is also an effect from frequencies that are odd multiples of a quarter wavelength.
73, Kent
AA6P
