Hi all,
Time to confess...
I have deleted my last message because I made some mistakes at writing my measurements results in post.? Here they are:
1)
I measured now the voltage at the PA PTT line when unconnected: +2.1V.? It should be at 0V through 10k resistor.
That is why I used a 1k parallel to GND in QDX to pull it down when inactive.
2)
When simulating the QCX PTT output by using +5V from PS the current into the PA PTT line was:
- at inactive PTT 0V: -3.3mA
- at active PTT +5V: +19mA
3)
When using the QDX modified PTT line (100R||470R) the current into the PA PTT line was:
- at inactive: -3.4mA
- at active (+4V): 13mA
So, yes Ron, you are right, something is wrong here at the PTT line input.? I was just rectifying the consequences not the cause.
But it works well.? Now I have to open it again and find the faulty one. The choice is very narrow: Q5 or Q6.? But faulty and not dead.
Anyway I would recommend to use parallel 100R to 470R to get higher PTT voltage at TX.
73 Bojan S53DZ
