Hello Rudi,
In hugen79 H4 schematic there ara two versions of the RX input bridge.
From version 4.2
R24 - 91 Ohm
R22, R23 - 51 Ohm
R25 - 11 Ohm
From version 4.2.1
R24 - 56 Ohm
R22, R23 - 240 Ohm
R25 - 49.9 Ohm
In my NanoVNA i use
R24 - 56 Ohm
R22, R23 - 49.9 Ohm
R25 - 11 Ohm
I also tested R22, R23 - 51 Ohm - does not make big difference.
The firmware i use is version 0.9.3.3 beta FAT16/FAT32 SD card by DiSlord. This combination of hardware and firmware gives good results up to 1.5 GHz.
The S11 up to 1.5 GHz is better than 50 dB.
The S21 up to 1.5 GHz is better than 60 dB.
Best regards
Bert
