Hello, how can i replace variable capacitor with varicap

Thread Starter

michael1978

Joined Jun 29, 2014
309
nice wekend to everybody
YES. R2 is the 120K ohm resistor. And C1 is the capacitor that I was referencing. But now here is a question that needs an answer: What frequency are you hoping to hear??? Also, those inductors may or not be the correct value. In addition, those inductors are physically very small and I am wondering if they are an appropriate value for tuning to the frequency of whatever radio stations you wish to hear.
sorry but you said 230k so that dont exist in circuits, frequency from 600hz to 1600khz....(wich one pick up the tunning), but i want just to learn ..
 

Thread Starter

michael1978

Joined Jun 29, 2014
309
"why in this circuits they don use diode?"
Please post a link to the webpage that has this horrible circuit.
Sorry Mr Audioguru, me i dont understand because if a put something first i try is working of not, but i rely did want to ask you about this question, You are Right. ;-)
 

Audioguru

Joined Dec 20, 2007
11,248
frequency from 600hz to 1600khz
No and no.
AM radio stations have carrier frequencies from 540kHz to 1600kHz. 600Hz is a low to medium audio frequency, not a radio frequency.

if a put something first i try is working of not
VERY poor English. You need to make a radio that works properly with a normal variable capacitor first. The horrible circuit you found will not work!
 

MisterBill2

Joined Jan 23, 2018
18,176
No and no.
AM radio stations have carrier frequencies from 540kHz to 1600kHz. 600Hz is a low to medium audio frequency, not a radio frequency.


VERY poor English. You need to make a radio that works properly with a normal variable capacitor first. The horrible circuit you found will not work!

I suggest being more polite, it seems that people from all over the world get into this website and it also seems that quite a few of them have less electronics/ electrical background than I do. That is why I try to share knowledge and insights with them. Education benefits most who receive it.

And the circuit is indeed not a very good one, although I can see that it may possibly receive a strong AM signal with a fair amount of distortion. I would not recommend the circuit to anybody, though. Better circuits are available, visit the "freeinformationsociety" website for a number of examples.
 

takao21203

Joined Apr 28, 2012
3,702
Recommend to get a DIY kit for soldering radio, this thread doesnt seem to be useful, theres nothing gained so far, besides the obvious that the circuit is not a radio, whatever it is.

Theres not difficult to on google radio of AM is that receive, or ???
 

Audioguru

Joined Dec 20, 2007
11,248
The horrible circuit has been copied by a few other websites. One website says that R2 produces regeneration but does not understand that R2 produces DC negative feedback and C1 prevents an AC output signal from reaching the input. Without C1 then the negative AC feedback is the opposite to regeneration which needs positive feedback.
One website has the high output impedance of this circuit wrongly feeding a low impedance speaker.
 
Top