Very interesting. I was quite shocked that you didn¡¯t use metric units for the calculations though. This would be my suggestion: use metric units.
JD
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On Jan 30, 2021, at 07:23, Barry Feierman <k3euibarry@...> wrote:
?Hello NANO VNA folks
I keep updating my NANO VNA talk after presenting at different club meetings. I've had my Nano VNA for about four months now, and each time I play with it I learn something new.
Questions raised by viewers made me reconsider how to explain PHASE and RESONANCE and especially what the SMITH CHART reveals.
It feels like PHASE is greatly misunderstood, with antennas.
I tried to come up with a simple mechanical analogy: GRAMPY pushing GRANDCHILD on a swing.
Even little grandkids know that GRAMPY has to push the swing at just the right time (PHASE) to increase the amplitude of the kid's swinging.
We all "know" that. If Grampy does not push at the right time, the grandkid complains.
Do antennas work the same way, with the feed line pumping in energy at just the "right time" to increase the current in the antenna?
The rig does not supply the electrons to the antenna (they were already in those copper or aluminum atoms).
The rig supplies, via the feed line, the instructions as to WHEN to push those electrons.
Think of the feed line like GRAMPY pushing the GRANDKID.
We use the Nano VNA most likely in our (warm) shack. But perhaps we are really interested in what the readings are at the ANTENNA junction.
By changing the feed line by a few feet (on 10 meters) I was able to convince myself that adding about a 1/4 wavelength of RG213 (6 feet) did ROTATE the impedance values on the Smith Chart. I "knew" what was going to happen, but still smiled when I saw it with my own eyes. Yet, adding 6 feet of coax (to a 100 ft feed line) did absolutely nothing to the SWR readings on 10m (28-29 MHz) to the REFLECTION COEFFICIENT, and to the RETURN LOSS.
So I added these slides to my newest PDF file.
The attachment is my latest rendition of a NANO VNA talk (as pdf slides).
If any clubs are looking for a speaker, I am all in. I learn a lot by giving a talk on a topic (I'm at a 9th grader understanding of the VNA)
73 and TU for all of the helpful suggestions. Feel free to pass on these PDF slides to others.
de Barry Feierman k3eui
<Nano VNA Analyzer Jan 28.pdf>
