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Next we can check at the outputs of the secondary windings of T1. These are the windings which feed pin 7 and pin 9 of
the Quadrature Sampling Detector (QSD), IC4. Now although the amplitude is a bit weaker now we can still observe it
quite well, even after the BPF adds some loss, and after the phase-splitter formed by these two transformer windings and
loaded by the Quadrature Sampling Detector's sampling capacitors C43-C46.
This is a bit tricky to see, because there is also an audio frequency component leaking back through the mixer, and other
unpleasantness. If you have a Digital Storage Oscilloscope you can switch on the 20MHz Bandwidth limiting on both
channels, and you can use it in Single-shot rather than continuous Run mode - then you can grab a screenshot like this
one below and see what is going on. The upper trace (Ch 1) is IC4 pin 7, the lower trace (Ch 2) is IC4 pin 9.
The oscilloscope probes for Ch 1 and Ch 2 were connected to the points indicated by the yellow arrows. It is easier to
hold the 'scope probes on these points, than on the pins of IC4 itself, since the IC is Surface Mount and a bit small.
