GC_ET_Schem.html
2019-10-23 13:42:03
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1. Pre-Amp
2. Roofing-Triad Differential Filter
3. Active-Log_limiter
4. Quad-MFB audio filter , variable f()
5. Double-Notched Differential-Phase Filter
6. Sharp Q20 MFB variable Filter
6. Audio out 0.5 W class-B
Each module presented can be constructed on a proto-board
and used as a stand-alone circuit.
Intra-State impedances are well matched
Standard Signal Input/Output is 1 V audio
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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.
***
*** 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.
_
Left is a Magnitude Plot of a typical Dual-Notch Circuit. Right is a 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.
Advantages are simple f(0) variation, which allows easy alignment of filters.
R(2) is the only component that needs adjustment for a +/- 20% change.
[Q will change only as the square-root of the delta-f(). ]
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the AFX B.A.S.I.C. Schematic
(first version)
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the AFX'V' Single Roof Filter Schematic
with Narrow Dual-Notch and Wide-Integrated Stages
Early version
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the AFX'V' with Variable f() PassBand (Best of Class)
with jFET controlled Variable f(0) and Three Roof Filters
(advanced version)
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the AFX Roofing-Triad-Filter
the AFX Active Limiter
the AFX Quad-MFB Filter details
Multi-FeedBack Active Filter Standard
(early basic version)
the AFX Differential-Phase Filter and Q20 Sharp filter
*** AFV_3RL-v2F-vQ-v1-S design :
*** (1) with Three Roof Filters
*** (2) with only Two MFB filter stages ( not sufficient for dual notch )
*** (3) with R(freq) controlled by a Two-Gang Pot
***
Schematic shows
24 All-Pass filters
used to replace two MFB Active PassBand Filters.
*** results are Very Good
Schematic shows
8 All-Pass filters
used to replace two MFB Active PassBand Filters.
*** results are Usable, OK.
*** Compared to the "AFV-3RL-V4F-D-VQ" version
(1) BW @ -3dB is wider ; 160 Hz vs 80 Hz.
(2) Dual Notch BW is wider ; 380 Hz vs 330 Hz.
(3) Variability of f(0) is much narrower ; +/- 50 Hz vs +/- 100 Hz