[PPRAANet] Tech Question Reference: neutralization in reference to amateur radio. 07/18/19

[Earl Watkins]

Greetings all,

If this is appreciated I would be willing to start compiling information
and giving a doc pack for the weeks tech question:
Tonight we discussed neutralization. As i wasn't planning this email the
hams with great information were not written down. I looked into
neutralization and this is what i found Please feel free to correct me or
give other information:

As my RF professor in college used to say "Amplifiers oscillate and
oscillators don't". Oscillators can be made from an amplifier circuit with
proper feedback. Because of this we know that there is a setup that will
cause oscillation in at least some amplifier circuits(i suspect this to be
many or most).  As I am not a tube guy I will give my explanation in the
transistor realm and allow a more knowledgeable tube user to translate.

If you look at the first link below on pg 56-57 there is an explanation, at
least in reference to transistor circuits. The best that I could gather is
that transistors have capacitive coupling between the first and second
transistor allows feedback of high frequency energy, RF. This can be
eliminated by injecting an out of phase feedback, see link 2 below. Even
though the the depiction linked is for audio waves the principle of
cancellation still applies to RF. A slick trick to this is that capacitors
and inductors cause phase shifts and by properly adjusting a capacitor in
the feedback circuit can shift the feedback to eliminate this oscillation.
The capacitors we discussed tonight being adjusted were likely for exactly
that purpose.


Using *amateur radio "neutralization" *as the search term i found the
following:

   - https://www.americanradiohistory.com/Archive-Bookshelf/Author-Groups/Donald%20Stoner/The-Transistor-Radio-Handbook-Donald-Stoner.pdf
   (pg 56 -57)
   <https://www.americanradiohistory.com/Archive-Bookshelf/Author-Groups/Donald%20Stoner/The-Transistor-Radio-Handbook-Donald-Stoner.pdf>
   - http://www.indiana.edu/~emusic/etext/acoustics/chapter1_phase2.shtml


Regards,

Earl W.

Earl Richard Watkins II
Phone: (785)639-1717
Call Sign: AE2RW