On 6/26/21 4:02 PM, Kent AA6P wrote:
I didn't initially notice Larry's comment that pulling the USB cable extinguishes the Battery LED. My NanoVNA-H4 does not operate that way so maybe the difference is the FM5324B chip.
The Battery LED in my unit only flashes below 3.6 volts so the indicator is useful in that one regard. Otherwise, the Battery LED is steady on whenever the unit is turned on.
The operation of this LED is very different with the NanoVNA-H4 and NanoVNA-H.
Here is a surprise. I have an AC Outlet Power Meter and decided to check the AC wattage when charging the NanoVNA-H4. I have three different AC to USB phone charger adapters. The wattage readings were 7.8 watts, 10.7 watts, and 11.5 watts using the three different AC adapters. All readings were higher than expected. The battery charge current must be quite high.
Measurements on my NanoVNA-H were all in the range of 1.5 watts to 1.7 watts. That seems much more reasonable.
73, Kent
AA6P
Or the chargers have wildly varying efficiency or (more likely) they have weird power factor/current waveform that "fools" the power meter.
In addition to the trusty Kill-A-Watt for AC, I have a couple USB power meters that are quite handy.? And, if there's still something weird looking, there's the trusty 0.1 ohm resistor and the scope to look at the current waveform.
