My understanding is that hugen pulled the initial firmware that allowed operation up to 1500 MHz because performance was so poor (probably especially true for those NanoVNA with oscillator chips that have trouble operating to 300 MHz). Subsequent firmware developers found they could get useable range extension by a change of mixer stimulus.
I have two NanoVNA's and have updated both of them to 1500 MHz operation. Above 900 MHz most of my measurements are s21 thru-loss. Between 900 MHz and 1 GHz I have about 30 dB of useable s21 measurement range on both NanoVNA's. Above 900 MHz increasing to 1.5 GHz the s21 measurement range gradually falls off to 20 dB on both units.
On each of my NanoVNA's, S11 measurements are acceptable up to 1 GHz but start to become suspect >1.2 GHz.
I consider the firmware upgrades (currently using hugen's 0.2.3 version) to be worthwhile for my two units. I might also add the new NanoVNA-H that hugen is marketing has the 1500 MHz firmware installed. So he must believe it is stable enough to use in his commercial product. The last thing he would want is bad marketing by including firmware that doesn't perform well.
- Herb
