GC_ET_Summary.html

2021-01-04    17:16:31

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 Summary:
This is a Research Project about  Phase-Filters for Narrow Channel CW reception,

   This is a Study about Differential Phase-Filters and includes these topical sections : 
    Roofing Triad Filter   &   Active Log-Limiter   &   MultiFeedBack Filters   &  Differential Phase Filters  &  Audio Amp.           

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       *** Designed for Easy Construction and Easy tuning and Superior CW audio filtering.
       *** Constructed and used daily for Amateur Radio CW (morse code) Operations on the Radio Bands. 
       *** The AFX CW audio filtering has near Digital Signal Processing quality as presented to the Ear.
      *** The vintage  LM324 OpAmp was chosen because the project frequency response and gain requirements are within bounds.

       *** Note that OpAmp null and balance trim-pots are not shown, and common by-pass caps not shown. 
       *** (1) for simplification
       *** (2) circuit designs are self-balancing and produce symetrical waveforms.
     

PreRequisite : 

This is not an academic Calculus based tutorial.  
It is expected that the reader will have
an understanding of Active BandPass Filter Concepts.   

All concepts presented herein are common to Active BandPass Filters
as presented in tutorials and academic course-work for Electrical Engineering students. 
ONLY the synthesis of common ideas into radically new approaches is different. 

"Your Imagination is more important than academic learning"
 

About this project : 

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This project is our Current research in Analog I.C.  Applications, 
as applied to CW (morse code) Radio Operations
... posted at www.GeoCities.WS/glene77is   
... posted at www.ResearchGate.net
... posted at Yahoo HW8 Group

Our Analog Project shows the evolution of filter design 
from common Active BandPass circuits into Active Phased-Filtered circuits.  
(1) is about Analog Electronic Technology applied to Amateur Radio CW operations.   
(2) is applied to Narrow Band-Pass Morse Code CW operations. 
(3) has produced a Series of Analog Filters aproaching DSP quality in CW operations.    
(4) Emphasizes Radical  Phase-Filtered  designs.
(5) Emphasizes Phased-Filters and Parallel-Channel-Filters to generate Dual-Notch effects. 

Our project's Applications could include in-lab analog instrument filters 
where the circuit is proto-boarded and no PC/computer required .

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Magnitude Plot of a typical  Dual-Notch Circuit.

                                                        Bode Plot of a typical PassBand group.  

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This is the basic equation for the Multiple-FeedBack active filter
which is used dominantly in this project. 
Advantages the Multiple-FeedBack active filter topology are :
(1)   simple f(0) variation, which allows easy alignment of filters. 
(2)   R(2) is the only component that needs adjustment for a +/- 20% f(0) change.
    [Q will change only as the square-root of the delta-f(). ] 



Commonly, we have chosen 5 nF, and f(0) = 700 Hz,
and standard circuit voltage of 1V audio.

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