[allan]

I tackled the setting up of the ALC loop and found everything worked as the book suggested except I was getting 3dB more output than that the documentation gave ie about +17dBm max instead of the recorded +13.2dBm fsd in the +10 setting.
The home brew detector test point reads about -2 volts so I'd guess this magnitude is too low forcing the output to go high by 3dB.
That extra 3dB RF output is constant from 200MHz down to about 12MHz, +2.5dB high at 400MHz and rises to +6.5dB at 5MHz, +8.8dB at 3MHz, +8.5dB at 1.5MHz and +6.7dB at 750KHz.
Harmonics are a bit high indicating the whole loop is running at too high an RF output.
Presumably I could either increase the detector output to deliver a greater feedback voltage to lessen the RF level by 3dB or alter the reference level to give the same results.
From the measurements, the detector output is dropping off below 5MHz resulting in too high an RF level so upping the 33pF coupling capacitor in the home brew detector to at least one order higher?
AM works OK insofar as setting it up on the meter. That has to be done prior to setting up the RF output versus meter readings.

On the other hand I could just add a 3dB pad in the output lead and pretend everything's fine.

I used a spectrum analyser rather than the power meter suggested in the set-up procedure. Because of the out of spec harmonics a power meter would have been a bit misleading because it would have summed the total power making the error seem even worse.

Allan