[HBR] IF transformers

[Hopperdhh at aol.com]

Pete,

You can get into a situation where  the stray capacitive coupling can cancel 
the inductive coupling.  Maybe  that is what was happening.

Dan K9WEK


In a message dated  10/4/2008 2:36:21 P.M. Eastern Daylight Time, 
radioconnection at gmail.com  writes:
Since I have several of these 85kc transformers to play with, I  tried
two in cascade with good results. I tried several different  coupling
cap values to couple the secondary of the 1st IFT to the primary  of
the second one to see what effect the value would have on  the
selectivity, and at what point the coupling became lossy.  Two  in
cascade worked fine. I was curious, and added a third transformer,  for
three in cascade. I ran into something odd: the two coils in  the
middle IFT didn't seem to behave right; as if there was no  mutual
coupling between them? This was even with the coils set for  max.
coupling, close together. I don't understand what I am seeing.  Adding
a small coupling cap from the high end of the primary to secondary  LC
circuits in the second IFT solved the coupling problem.

Pete  




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