I've measured windowline many times using the NANO - something I can not
easily accomplish with the HP 8753C. Be sure the NANO is not connected to
any conducting cabling, chargers, USB cables, or sitting on or near
anything conducting. At HF frequencies the NANO is small enough to not
influence measurements. However, if it is connected to anything
conducting, it is no longer "small" as a function of frequency /
wavelength.
The attachment indicates you have connected the NANO to a PC. The NANO
effectively becomes much larger at RF frequencies as its connected to: 1)
the USB cable, 2) the PC, and 3) the house wiring, and finally, 4) the
power grid. This will greatly influence correct readings of windowline.
Measurements must be made with the NANO alone.
Dave - W?LEV
On Tue, Feb 15, 2022 at 4:40 PM Kevin Zembower via groups.io <kevin=
[email protected]> wrote:
I'm wondering if the correct way to measure the length of window line
with a NanoVNA is fundamentally different than that of measuring coax.
I'm following the method described by Arie
(/g/nanovna-users/message/26832). I have 5.175m of "JSC
1320 300 Ohm Ladder Line 300 Ohm 20 AWG / 7 Strands Bare Copper". That's
a quarter wavelength of 20.7m, or a frequency of 14.5MHz.
The first step is to sweep it to determine the velocity factor. Yet,
when I sweep from 12-17MHz, I get the Smith chart attached. There's no
point when the impedance is close to zero.
Am I doing something wrong (most probable), or is measuring the length
of window line with an NanoVNA fundamentally different than measuring coax?
Thanks for your advice and suggestions.
-Kevin
KC3KZ
--
*Dave - W?LEV*
*Just Let Darwin Work*
