Hi folks, me again...
Just popping in here to you on research I've done over this.
IF anyone wishes, you can find more Op-Amp "precision rectifier" designs here...
http://sound.whsites.net/appnotes/an001.htm
But, in light on the many complaints I've received thru the years of working behind the counter and as a backyard "garage" repair "contract" worker - I've come across many different radios that are "derivatives" of the original it was supposed to replace yet fall flat on the receiver performance - where in some cases - ENGAGING the ANL/Noise Blanker circuits induced more noise into the receiver than it removed.
I'm seeing some issues and not to alarm anyone - but - did anyone ever notice the ANL circuit works a lot like a bridge?
I also found several Radio Manufacturers that have "flawed" the ANL process.
So we need to re-look back to the original design and realize that whether Cobra's 148GTL or Uniden's HR2510 or radios in-between the platforms of these two (low level and High-level modulation) are a whole slew of configurations and designs of various values but all are based upon the premise of a bridge circuit.
The problem is, many ANL circuits are "copies" of the original and the lack of understanding how they need to work is - well, evidently disheartening. Many have missing portions of the ANL bridge that if it had been installed, could help the end user from having to complain and demand it to be fixed - How? It's a receiver design - so hence the plea to you the reader as to the mess the ANL shortcomings are, that we need to pay more attention to their (makers) use of the design.
The link above references a term called "virtual ground" which I refer to how the signal floats at potentials below foil ground - meaning that foil ground is more positive at times than the signal mean (A standard deviation term) which will vary as frequency and phase or vector of voltage and current and the maximum effects of deviation are as the signal propagates across R1 and R2 with the polarized cap (reversed polarity) in the middle.
So as you'll see many of the ANL circuits are missing key components especially at the trailing arm output where the Diode and Cap / Resistor or whatever component used, offsets the signal clipping and can smooth the effects of distorted noise that occurs because the part is missing. Or not properly accessing the "virtual ground". The major complaint is how the receiver seems to sound within noise abatement off, versus the ANL NB usually tied together on - and why when it's on, it's worse than when it's off? I'm often asked - if they can be made separate - in many instances they cannot be separated so they work together and make the mess of the otherwise, a well mannered receiver.
Will add more as time allows...
:+> Andy <+:
Just popping in here to you on research I've done over this.
IF anyone wishes, you can find more Op-Amp "precision rectifier" designs here...
http://sound.whsites.net/appnotes/an001.htm
But, in light on the many complaints I've received thru the years of working behind the counter and as a backyard "garage" repair "contract" worker - I've come across many different radios that are "derivatives" of the original it was supposed to replace yet fall flat on the receiver performance - where in some cases - ENGAGING the ANL/Noise Blanker circuits induced more noise into the receiver than it removed.
I'm seeing some issues and not to alarm anyone - but - did anyone ever notice the ANL circuit works a lot like a bridge?
I also found several Radio Manufacturers that have "flawed" the ANL process.
So we need to re-look back to the original design and realize that whether Cobra's 148GTL or Uniden's HR2510 or radios in-between the platforms of these two (low level and High-level modulation) are a whole slew of configurations and designs of various values but all are based upon the premise of a bridge circuit.
The problem is, many ANL circuits are "copies" of the original and the lack of understanding how they need to work is - well, evidently disheartening. Many have missing portions of the ANL bridge that if it had been installed, could help the end user from having to complain and demand it to be fixed - How? It's a receiver design - so hence the plea to you the reader as to the mess the ANL shortcomings are, that we need to pay more attention to their (makers) use of the design.
The link above references a term called "virtual ground" which I refer to how the signal floats at potentials below foil ground - meaning that foil ground is more positive at times than the signal mean (A standard deviation term) which will vary as frequency and phase or vector of voltage and current and the maximum effects of deviation are as the signal propagates across R1 and R2 with the polarized cap (reversed polarity) in the middle.
An Idealized ANL and Smoothing filter for Detectors...
So as you'll see many of the ANL circuits are missing key components especially at the trailing arm output where the Diode and Cap / Resistor or whatever component used, offsets the signal clipping and can smooth the effects of distorted noise that occurs because the part is missing. Or not properly accessing the "virtual ground". The major complaint is how the receiver seems to sound within noise abatement off, versus the ANL NB usually tied together on - and why when it's on, it's worse than when it's off? I'm often asked - if they can be made separate - in many instances they cannot be separated so they work together and make the mess of the otherwise, a well mannered receiver.
Will add more as time allows...
:+> Andy <+:
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