开云体育

On 7/18/22 8:24 AM, Observer wrote:

I inserted my nanoVNA, ( fully calibrated as swr ) into the input of my ATU100 auto tuner, with power off.
I got anything but an swr reading. Am I doing it right ?
Before test, I inserted the 50 ohm load at CH0 , and it showed 49.70 ohms 1:1.0025 . So, I assume, my vna is calibrated ok

Some ATUs "remember" the tuning setting when power is off, others don't. (i.e. some use latching relays, others don't).

What you should see, looking into the tuner, is the S11 with a dip at the tuned frequency, and not other places. As you change the tuner's Ls and Cs, the dip moves both in depth and frequency.


In general, the NanoVNA doesn't put out enough power for an auto tuner to actually do the tune cycle. If you have a tuner with a serial remote control (or equivalent) like the AT200PC, you can send inductor up/down and capacitor up/down commands and run a tuning algorithm on a PC that looks at the NanoVNA's measurements.

This is non-trivial.

The answer(s) to your question depends on what you want to know about it and what type of Tuner it is.

For example, I have a homemade manual Tuner that I built many years ago, and, having learned a lot more about impedance by now, wanted to know what the characteristics of the Tuner were as far as impedance and the effect that it has when in line and in bypass. I calibrated the vna to the end of my patch cable to a 50 ohm dummy load over 2-30 MHz, then connected the load to the output of the Tuner and the cable to the input of the Tuner. It was pretty bad.... both in line and bypass. I cleaned up the wiring and improved it, although it is still not ideal.

The other way I use the vna with the Tuner is to find and record the settings for a range of frequencies in each band. For that, I use both channels displaying swr, logmag, phase and the Smith Chart. By observing the changes in the Smith Chart, I can dial in the settings for the desired frequency and tweak the response around it.. I like to try to get the logmag down to -40 dB at that frequency if I can, but that is only at the exact frequency.