Hi Fred, can you give us a hint as to what your procedure for "D" is?
. . . Where did I go wrong?
. . . Where can I get answers to the questions you pose that will lead me to your answer to "D".
> can you give us a hint
Yes.
First, look again at the definition of ORA: "the peak short recorded wavelength response"
Next, remember that "peak response" implies an amplitude measurement (not phase).
The VU meters on the tape machine (when switched to read the output of the playback amplifier) are perfect for this purpose.
Owing to the VU's (or PPM's) analog meter movements, you can easily discern the amplitude peaking as you adjust the read head (aka the play head) azimuth.
So put away the oscilloscope and look at the VU meter(s).
Use the (coarse azimuth alignment) 8kHz tone first, and peak that by adjusting the read head azimuth.
Then, still looking at the VU meter, try to again peak the finer resolution, 16 kHz azimuth alignment tone.
This is the very definition of finding the ORA (optimum read head azimuth).
> Where did I go wrong?
Unable to see what you're doing, I'm unsure.
It's possible that by using the oscilloscope (with adjustable gain in its independent vertical deflection amplifiers) you're only making the task more difficult.
If for some reason you absolutely need to use an oscilloscope for your amplitude measurements (maybe you don't have VU meters?) then first try switching the scope out of its X - Y display mode to read only the amplitude of the displayed waveforms.
> Where can I get answers to the questions you pose that will lead me to your answer to "D".
Any good university's electrical engineering library would be a starting point. Or come take an ATAE course where you'll receive a suggested bibliography, in case you want to get into the weeds of analog magnetic tape technology.
But as I'm saying here, adjusting ORA is actually very easy. Just look at the VU meters.