Another experiment. What difference does the NanoVNA CALIBRATE>POWER setting produce in the VNA’s signal level?
The Setup:
VNA S11 calibrated to start/stop of 50 MHz–90 MHz, 401 sweep points. Traces are LOGMAG & Smith.
TinySA Ultra set to start/stop of same values as VNA.
Attach 30db external attenuation to SA and set LEVEL>EXT GAIN to -30db so what you see on the screen is the true current the VNA is sending.
Set VNA to CW mode at 60MHz, leaving CALIBRATE>POWER on AUTO. Then freeze trace 1 (yellow).
Set VNA CW mode at 70MHz, . Activate SA trace 2 (green). Set VNA CALIBRATE>POWER to 2mw. Freeze trace.
Set VNA CW mode at 80MHz, CALIBRATE>POWER to 8mw. Activate SA trace 4 (red). Freeze trace.
Activate 4 SA markers. Set 1, 2, & 3 to trace 1, 2, & 4, respectively. (ignore marker 4).
What happens? The VNA CALIBRATE>POWER>AUTO produces the same signal as CALIBRATE>POWER>2mw. AUTO is the same as the lowest POWER setting. A good design choice for safety’s sake. CALIBRATE>POWER>8mw is higher by almost 10mw than AUTO/2mw. If you look at the marker values at the top of the TinySA screen, you see that they are just as expected within the resolution of the SA.
Notice all the spurs around the highest power (trace 4) setting. In the pictures, the SA’s LNA is OFF. If I turn it ON, both the AUTO and 2mw traces also show spurs though smaller than those produced at 8mw.
Picture 1 of both devices
Picture 2 a close-up of the tinySA I hope clear enough to read the marker values
Picture 3 is just a shot of my best (and most expensive) little attenuator: Pasternack, 30db, 2W.
