What? No mention of monitoring using a Trapezoid pattern?
Well this is one of those topics where many of us will never try it since the setup is more complex because we need two inputs to the scope instead of one. Still, when using a linear amplifier on AM, the trapezoid pattern is really useful to get the tuning correct. A slight increase in the loading capacitance (more C) will have a pronounced impact on reducing the positive polarity peaks. You can still see this on the conventional envelope pattern, but gain compression is harder to see. So ideally we have both types of scope display available.
Another factor on topic here is that many class C plate modulated rigs have imperfect neutralization. With my Gonset G76, which has a neutralized final (6DQ5), I find the NC setting somewhat band dependant. Here when it is off, I need to back off the drive a little, and say 'Hellooo' into the mic while peaking the RF driver tuning condenser a little each side until my positive peaks are max'd out. Then adjust the drive level to the usual value.
Jim
WD5JKO
