[R-390] Best approach for SSB mod on R-390A

[2002tii]

Dave wrote:

>Also, without manual controls, the detector has to guess the 
>operator's intentions, based on, say, tuning rate.

For this reason, it's better to have the SAM detector in the box with 
the tuning -- you can then either turn the oscillator off and revert 
to an envelope detector for tuning around, or (my preference) just 
center the oscillator during tuning so one hears the carrier 
heterodynes.  I prefer to hear the carrier heterodynes while tuning, 
and have found with my SAM designs that it's not difficult to adjust 
the PLL characteristics so that the action is invisible while tuning, 
even if the SAM demodulator is external and doesn't know when you're 
tuning.  IMO, the need for manual guidance into lock is a design of 
necessity (because the loop characteristics were ill-chosen and the 
PLL therefore did not exhibit benign behavior while tuning), not an 
original ergonomic specification.

>Sometime I'll build one or more and report my experience using them 
>vs the SE-3.  Or if anyone local has built one, let's get get 
>together and try it out next to my SE-3.

One I didn't mention in that post because I don't know of an on-line 
copy of the manual: the Drake R8B has a truly excellent SSSAM 
detector.  If you're going to build, a study of that schematic and 
the accompanying discussion of the theory of operation will 
undoubtedly be very rewarding.  Drake chose to turn the oscillator 
off and revert to an envelope detector for tuning around, so the PLL 
loop dynamics would probably need to be tweaked to use it in "tuning 
with the oscillator on" mode.  (I keep meaning to convert mine, but 
haven't gotten around to it.)  Of the links I posted, my expectation 
from a not very thorough design review is that the Surrey Electronics 
unit may be quite good, but I have never used one.

Best regards,

Don