Having calibrated to a 300-ohm standard, then why not multiply the measured
value by 6? I believe there is a place in Saver for a multiplier or
arithmetic.
Note in your 300-ohm cal. presentation of the measured data of S11, VSWR,
you show a dip to 1:1 between 41 and 124 MHz (I can not read the closest
labeled point). That also shows extremely near the center of the Smith
Chart. You have placed the marker at this position. Since you have
calibrated with 300 ohms, the center of the chart is now 300 ohms, not
50-ohms. This is also true of your S11, VSWR data measurement.
This practice is quite common when using the Smith Chart. One can
'normalize' the chart center to about anything within the instruments range
of impedances. Many times, we use a 'normalized chart' and represent the
chart center as 1, unity. Then, in working the problem at hand, one
multiples everything presented on the chart by the characteristic
resistance in which one is working - most times, 50-ohms. In your case,
you are working in a 300-ohm system.
Dave - W?LEV
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On Mon, Feb 17, 2020 at 7:17 PM goscickiw <goscickiw@...> wrote:
Is there a way to make the NanoVNA show the SWR as close to 1:1 on 300 ohm
antennas when measuring directly without an impedance transformer, while
still showing correct impedance? I need to measure just the antenna, so
that the cables and impedance transformers don't affect the result. I tried
calibrating with 300 ohm load, but then it shows 300 ohms as 50 ohms when
measuring impedance.
Attached example - FM folded dipole readout with NanoVNA calibrated with
50 ohm load, and with 300 ohm load
--
*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*
