Thanks to Nick for the further gen on the Terman 'Measurements..' book, I
have not been lucky enough to find that. I would be interested in a copy of
that bit if you can manage it. I am QTHR for the last 25 years.
To Mike yes I do use the steady signals of the 'beacons' for tests, but what
does S9 mean?? Its a strong signal but is it 10uV/m or 1V/m. Most of the
radios I have have S-meter sensitivity controls so you can set S9 at
whatever you like!  I'd love to tell you by how much you have improved your
system. There is no doubt you are much stronger with me now. I hesitate to
mention the spacer (it would be regarded as 'snipeing' in other areas these
days!) but before your mods, the spacer registered a 6dB  S/N ratio on
FFTDSP4 (which is I think 'in 100Hz bandwidth' ).
Now the spacer is a good 10dB S/N and would be copiable as a hand keyed
mosre transmission in 2.5kHz bandwidth. It has the advantage of
'fingerprinting' your transmission and I have posted your appearance to my
local DX cluster before you have finished sending the call sign in QRS mode.
Your main carrier now produces a signal that is on a par with that I receive
from John (20dB S/N on FFTDSP4), though the orientation of my loop has some
effect.
Just a thought as you are using a mixer source...have you tried keying one
crystal oscillator? I find that quite clean and stable. It might be an easy
mod.
After the comments from Dick I'm now off on the track of a Level Measuring
Set! I think I know where there is a 20MHz Racal job.
Cheers de Alan G3NYK