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Pri-sec phasing



---------- Forwarded message ----------
Date: Thu, 9 Oct 1997 16:08:32 +1200
From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
To: tesla-at-pupman-dot-com
Subject: Pri-sec phasing

Hi Greg, all,
              After a night of agonizing, I decided to recheck my 
measurements of yesterday. I started off on a bad note. It turned out 
that the generator impedance was upsetting things significantly so I 
ran the generator through a high frequency stepdown transformer to 
turn it into as near a voltage source as I could. I had to keep an 
eagle eye on three things - amplitude response of the system, 
frequency on the generator and a minor dip in the primary near/at 
resonance. The last one is a real dog because it failed to coincide 
with maximum amplitude response. I reasoned this was because primary 
voltage was slipping a little due to loading. I also had to check 
tune when probing other portions of the resonator. When I say 
probing, I mean sniffing as a direct connection completely upsets the 
applecart due to low resonator capacitance.

     Going on primary dip (quite minor), the response at the top
(electric field) looked to be around 90 degrees with no topload. This 
reduced to something above 45 degrees with the topload I currently 
have. Going on amplitude response, the same differences applied but 
the phase shift was a lot less suggesting that the dip is the one to 
go for if the generator impedance is not 0 ohms. Yesterday, I was 
going on amplitude response alone which would appear to be a mistake.
     I also obtained similar results when probing the base or in 
close proximity to it. So there appeared to be little phase shift 
from top to bottom at resonance which, if one thinks about the ruler 
analogy, would appear to be correct.
     Then I injected a signal directly into the resonator base using 
the stepdown transformer. This time, I got the expected phase 
difference between the base and top end.
     
     So what is going on? At first glance, the coupled system 
scenario is behaving remarkably as though it is lumped. *However*,
my two points about lack of coupling from primary to resonator top 
stand. The toroid doesn't measurably affect the primary.

     My answer is that the "ruler" is responding quite differently to 
the two different methods of driving. In the coupled case, it is 
being rattled part way up (and definitely *not* over its whole 
length). In the second case, it is as though the bench vise is being 
waggled underneath the ruler. I surmised this some time ago but 
didn't realize the implications on system behaviour.

    Anyway, I am hereby admitting errors in my previous measurements 
and would welcome any comments anyone has to make. In summary it 
would seem that, without a topload present, there is little to 
commend pri-sec phasing *at resonance* and I cannot emphasize that 
strongly enough because the phase shift is extremely sensitive to tune
(including secondary spark emission).
     *HOWEVER*, adding either a topload or extra ion cloud/spark 
capacitance pulls the relative phases much closer together so it 
would seem that topload or not, arranging the pri-sec winding senses 
to be the same is still the best idea.    

In apology,
Malcolm