Hi all,
The outcome of my tests with the QDX connected to the 50W class C PA (for FT-8) is as follows:
- QDX with T1 3:2, operated at +10V DC
- 50W PA operated at +18V DC
- direct BNC 50 Ohm connection from QDX output to the PA input
- direct 3.5mm PTT cable connection between them
I get approximately 20W output power into a 50 Ohm D.L. on 20m without overheating of either equipment.
I had to improve the QDX PTT +5V output line for that to work well:
- 100R 0604 parallel to R10 470R,
- 1k from Q12 drain to GND.
This was necessary to come closer to the QCX PTT like output.
With +18V DC the PA I.L. at RX (PTT = 0V) is at 0.4 dB on 20m, which is easily overcome by a QDX great sensibility.
I am quite happy with what I got.
73 Bojan S53DZ
