Hi Greg,
fine pictures except the content.
The waveforms looking strange to me. Lets have a look at 1.8 MHz. The gate voltage is going down to -2V! Why negative? I guess not from the IC503. The voltage is >= 1V for around 70% of the period. The part of the waveform with voltage around 1 V is wrong. The drain voltage is low when the FET is ON. The duty cycle is around 70% for both groups. It looks like the FET are switched on by gate voltages >= 1V, so for 70% of the period. An overlapping ON is bad.
For 28 MHz the FET are between ON and OFF all the time. The gate voltage stick at a medium value and couldn't go to LOW and HIGH. Something is blocking "large" voltage alterations.
So I have some more questions:
- Where did you clip the probe GND to the QMX?
- How long is the ground lead from the probe to the QMX?
- Do you use the original BS170 from the kit?
- Could you show waveforms at the connection T501 - L502, at the other side of L502 and at the secondary winding of T501 for both bands?
- Could you show detailed photos from the PA and from T501 from both sides to see the windings
73, Ludwig
