Hi guys,
I tested something else and made comparisons with my external SWR meter. I think, 5k ist not enough at R36. More a value between 1k5…2k2. I remove the R36 SMD resistor now completely and replace it with a 10k spiral potentiometer for better adjustment:
After this I repeat some SWR measurements and play around a little bit with the values. At the end I found 1k5 as best compromise. I have results near reality at 20m-10m and between, but at the low bands 80m-30m the shown SWR is a little bit to low than it should be, but not so much.
I use the PA50 more for portable so it is more important that the function is better above 10Mhz than lower.
In general I think, it would have been better if the protection was only effective from an SWR of 2.5 or 3 and not already start with only 2.0 . I’m sure, that would not be a problem for the finals, the most TRX do it so.
At the end I wouldn’t say “Don’t buy this amplifier”. We are hamradio operators and can solve such problems themselves. Aside from the SWR issue, it’s a good amp I think and a good add-one for portable.
For more comfort I build with an ESP32 (TTGO T-DISPLAY) a small device, which makes a Blutooth connection between the ESP32 and my IC-705, get it’s CAT data and switch the PA on/off with a 4N25 and generate an analog band switching signal for automatic switch the band filters in the PA (the IC-705 has no bandswitching output):
I setup the PA50 for XIEGU band switch protocol for this. I’m not a friend of VOX-controlled amps 
.
The same I use with my second amp too, a XIEGU XPA125B, too.
73 Heiko, DL1BZ