Is this circuit Diode Charge Pump AM-FM Demodulators

Thread Starter

michael1978

Joined Jun 29, 2014
309
Hello Sir, i thought is Diode Charge Pump AM-FM Demodulators because i have some tutorial and i understand and i know the value of components to select ok ,in other words i know to configure components,, but what for demodulator is this circuit? how they call it to search in google maybe i can find some toturials thnx…….
 

MisterBill2

Joined Jan 23, 2018
4,574
Actually, this is indeed a diode charge pump FM detector, but it is not a very effective type. And it does need a very well limited input signal to deliver any reasonable output.
 

Audioguru

Joined Dec 20, 2007
11,251
The NPN transistors are wrongly shown as PNP.
I have seen many AM-FM radio circuits but have never seen one with a charge pump.
The 0.01uF value of C28 is so high that it will completely kill the 10.7MHz of an FM IF amplifier. It might be OK for AM.
 

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jjw

Joined Dec 24, 2013
505
The NPN transistors are wrongly shown as PNP.
I have seen many AM-FM radio circuits but have never seen one with a charge pump.
The 0.01uF value of C28 is so high that it will completely kill the 10.7MHz of an FM IF amplifier. It might be OK for AM.
The IF used here is about 120kHz
 

MisterBill2

Joined Jan 23, 2018
4,574
C28 is probably used for de-emphasis but it is wrong for the FM broadcast band:
C28 is the pulse integrating capacitor, not for de-emphasis. The charge pump circuit is not used in broadcast receivers because it is not as easy to make it in production, since the tolerance of some parts is a bit picky. That is why most folks are not familiar with it.
And yes, those transistors are actually NPN devices, the emitters are simply drawn wrong.
 

MisterBill2

Joined Jan 23, 2018
4,574
Michael has been talking about broadcast band FM radio detectors here and on other websites.
FM detectors that are immune to interference are a very interesting challenge for those who build receivers that include detectors for FM, especially fairly narrow FM, such as is used in amateur radio communications. Most commercially available discriminator and ratio detector transformers are for 10.7 MHz while most ham receivers use other frequencies for their final IF. And while there are lots of explanations around as to how they work, creating an optimized transformer for either is not a small task.This is why the PLL FM detector is often a better choice, although the quadrature detector is much more common, because it works and it is cheaper and simpler.
 

Thread Starter

michael1978

Joined Jun 29, 2014
309
C28 is the pulse integrating capacitor, not for de-emphasis. The charge pump circuit is not used in broadcast receivers because it is not as easy to make it in production, since the tolerance of some parts is a bit picky. That is why most folks are not familiar with it.
And yes, those transistors are actually NPN devices, the emitters are simply drawn wrong.
Hello MisterBill2, is this circuis Diode charge pump, you told one time, but Jjw say that is pulse COUNTING?
 

MisterBill2

Joined Jan 23, 2018
4,574
Hello MisterBill2, is this circuis Diode charge pump, you told one time, but Jjw say that is pulse COUNTING?
Yes, the charge pump provides the counting by integrating the power delivered by each pulse of the carrier, as the pulse spacing varies with frequency. So it is indeed a counter, but not a digital counter. It is a pulse power integrating sort of counter.
 

Thread Starter

michael1978

Joined Jun 29, 2014
309
Yes, the charge pump provides the counting by integrating the power delivered by each pulse of the carrier, as the pulse spacing varies with frequency. So it is indeed a counter, but not a digital counter. It is a pulse power integrating sort of counter.
Thank you MisterBill2, for explanation………….:);)
 
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