RF converter(mixer), i learn here rf mixer, but this one is a little complicated help

Thread Starter

michael1978

Joined Jun 29, 2014
309
Hello,
I learn here about rf mixers,
and i take from one book complete receiver, so only one little bit i dount understand, it is complicated
here i put the circutis
i select with black line, what i dont understand, can somebody help me a little bit, so i put also in pdf if you dont see picture
fm complete.png
 

Attachments

Ylli

Joined Nov 13, 2015
799
Q3 is configured as an oscillator. The oscillator tuning uses parts L1x (FM Osc), C3, C17, C18, C24, and varicap D3. Incoming RF is also applied to the emitter of Q3, and is mixed with the oscillator by non-linear operation of Q3. The output at the IF frequency is couple through T1 to the rest of the receiver.
 

Thread Starter

michael1978

Joined Jun 29, 2014
309
Q3 is configured as an oscillator. The oscillator tuning uses parts L1x (FM Osc), C3, C17, C18, C24, and varicap D3. Incoming RF is also applied to the emitter of Q3, and is mixed with the oscillator by non-linear operation of Q3. The output at the IF frequency is couple through T1 to the rest of the receiver.
OOOhhhn Thank youuuuuuuuuuuu………………God bless You...…..
i have just more question, do you see L2, what is that to block high frequency of something else,
do exist formula for oscillator wich sort is, clapp oscillator , of other one? and also for L2 is any formula?
i forget and L4 C16 C23 what form tank circuit? if yes wich resonance must be?


:):):):):):)
 

AlbertHall

Joined Jun 4, 2014
8,533
L2 is tuned by C22 and C17A to the desired RF frequency. This passes only the receive frequency on to Q3, the mixer/oscillator.
 

bertus

Joined Apr 5, 2008
20,102
Hello,

For better understanding of the RF path, The powersupply rail and the ground are connected together for RF by C2, the 0.1 uF capacitor.
For RF L2 and the combination C22 and C17A are making a parallel resonance circuit.

Bertus
 

Thread Starter

michael1978

Joined Jun 29, 2014
309
Hello,

For better understanding of the RF path, The powersupply rail and the ground are connected together for RF by C2, the 0.1 uF capacitor.
For RF L2 and the combination C22 and C17A are making a parallel resonance circuit.

Bertus
Hi Bertus....Thanks,
what dou think about, about L4 C16 C23 what form tank circuit? if yes wich resonance must be?
 

bertus

Joined Apr 5, 2008
20,102
Hello,

I think L4 and C16 are a filter for rejecting IF back.
(no value of L4 is given, but the circuit has a fixed frequency).
C23 is a coupling capacitor.

Bertus
 

Thread Starter

michael1978

Joined Jun 29, 2014
309
Hello,

I think L4 and C16 are a filter for rejecting IF back.
(no value of L4 is given, but the circuit has a fixed frequency).
C23 is a coupling capacitor.

Bertus
GoodMorning Bertus, now almost i understand all, i go to search on google for more detail, Greetings....:):):);)
 
Last edited:

Thread Starter

michael1978

Joined Jun 29, 2014
309
Hello,

I think L4 and C16 are a filter for rejecting IF back.
(no value of L4 is given, but the circuit has a fixed frequency).
C23 is a coupling capacitor.

Bertus
Hi, i search in google, i dont understand so good, filter for rejecting if back, i know lowpass highpass bandpass, but what for resonance must i select? is any formula
 
Last edited:

bertus

Joined Apr 5, 2008
20,102
Hello,

Look for "notch filter".
A notch filter can be a parallel resonance circuit in series with the signal path or a series resonance circuit accross the signal path.

Bertus
 

Thread Starter

michael1978

Joined Jun 29, 2014
309
Hello,

Look for "notch filter".
A notch filter can be a parallel resonance circuit in series with the signal path or a series resonance circuit accross the signal path.

Bertus
Ahh notch filter i hear about it,now i gonna find on internet, thnxxxxx have a nice day
 

danadak

Joined Mar 10, 2018
3,614


Basic response of a notch filter, basically used to suppress a narrow range
or specific frequency. A similar, but not same, is a "Band Stop" filter, used
to suppress a range of frequencies.


Regards, Dana.
 

Thread Starter

michael1978

Joined Jun 29, 2014
309


Basic response of a notch filter, basically used to suppress a narrow range
or specific frequency. A similar, but not same, is a "Band Stop" filter, used
to suppress a range of frequencies.


Regards, Dana.
Hi, Dana, and which are those frequency in this circuit?
 

Thread Starter

michael1978

Joined Jun 29, 2014
309
Q3 is configured as an oscillator. The oscillator tuning uses parts L1x (FM Osc), C3, C17, C18, C24, and varicap D3. Incoming RF is also applied to the emitter of Q3, and is mixed with the oscillator by non-linear operation of Q3. The output at the IF frequency is couple through T1 to the rest of the receiver.
Hello Ylli, RF is applied to the emitter and L1x (FM Osc), C3, C17, C18, C24, and varicap D3 is apllied to collector?and output is from collector? i dont understand because i thougt the signals must be input to rf to base and local oscillator to emitter like i learn here and internet?
 

Ylli

Joined Nov 13, 2015
799
There are three basic transistor amplifier configurations. Common Emitter (CE) where the emitter is 'grounded', the input is to the base, and the output is from the collector. Common Collector (CC) where the collector is 'grounded', the input is to the base, and the output is from the emitter. Then there is the Common Base (CB) configuration. Here the base is 'grounded', the input is to the emitter, and the output is from the collector.

In this case, the circuit is configured as an oscillator, and input is to the emitter as if this were a Common Base amplifier. The fact that it is also oscillating, and with normal nonlinearities, the stage asks as a self-contained converter.
 

Thread Starter

michael1978

Joined Jun 29, 2014
309
There are three basic transistor amplifier configurations. Common Emitter (CE) where the emitter is 'grounded', the input is to the base, and the output is from the collector. Common Collector (CC) where the collector is 'grounded', the input is to the base, and the output is from the emitter. Then there is the Common Base (CB) configuration. Here the base is 'grounded', the input is to the emitter, and the output is from the collector.

In this case, the circuit is configured as an oscillator, and input is to the emitter as if this were a Common Base amplifier. The fact that it is also oscillating, and with normal nonlinearities, the stage asks as a self-contained converter.
OOh sorry now i undestand more, this is an oscillator and is determined by L1x (FM Osc), C3, C17, C18, C24, and varicap D3 (you told me also in begin), those have one frequency right and this oscillate, but where is the second frequency to mix it? this now i dont understand....
 

AlbertHall

Joined Jun 4, 2014
8,533
J
Common Collector (CC) where the collector is 'grounded'
Just because it is common collector doesn't necessarily mean that the collector is grounded.
The circuit below is a grounded emitter, common collector circuit. Its characteristics match 'common collector' - high input impedance, low output impedance.
upload_2018-10-29_17-18-15.png
 

Thread Starter

michael1978

Joined Jun 29, 2014
309
J

Just because it is common collector doesn't necessarily mean that the collector is grounded.
The circuit below is a grounded emitter, common collector circuit. Its characteristics match 'common collector' - high input impedance, low output impedance.
View attachment 162715
Hi Albert, i try to understand that circuit oscillator so i build in ltspice, i dont know how to correct it, to understand good, and formula,
i build this one
Naamloos.png
 
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