i remove only variable capacitor, and bb112 is 500pf and something, so i connected in parralell varicap and inductor and i make dc pach, with wiper 100Kohm, so i hear only noiseHello,
To adjust the varicap, one must have a DC path.
I do not see how to create this DC path.
You could have a look at the attached PDF, where several circuits with varicaps are given.
Bertus
but i dont know how to make antenna thnxYou need to post a schematic of EXACTLY how it is connected. My interpretation of your description is the the varicap is directly in paralled with the inductor. If that is the case then any DC tuning voltage you are trying to inject will be shorted out by the inductor.
Les.
You need to post a schematic of EXACTLY how it is connected. My interpretation of your description is the the varicap is directly in paralled with the inductor. If that is the case then any DC tuning voltage you are trying to inject will be shorted out by the inductor.
Les.
but what to do?
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i connect this one (how they call) one small speaker to put in your earThe first two transistors amplify the radio frequencies (a few stations) with no gain control so they are overloaded when there are strong local stations. The third transistor amplifies the radio frequencies even more, again with no gain control. There is no AM detector which is usually a diode.
What do you have connected to its output?
It is called an "earphone" and you need a power amplifier to drive it.i connect this one (how they call) one small speaker to put in your ear
thank you a lotttttttttttttttttttttt for time, but please can you help just a little bit, is good connected varactor? and i need a diode, and power amplifier,and why in this circuits they don use diode, "what for am radio is" and one more question i use this inductor is problem???? lookIt took a few minutes for this website to post my reply so I tried again and again. I deleted the copies.
This receiver looks a lot like a regenerative receiver with R2 being the feedback element. What I can offer is that adding the varicap circuit shown in the second circuit the feedback portion is greatly disrupted. Note that neither end of the tuned circuit is near ground potential and so it is not a good candidate for changing to varicap tuning. For that to be possible you need a circuit with one end of the tuned circuit grounded..hello, can somebody help me? i found this am receiver, but is using variable capacitor,
how can i replace of do with varicap this circuits(i hava varicap bb112)
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hello, just to ground one wire from tuned to ground and that is? thnx mannn...;-)This receiver looks a lot like a regenerative receiver with R2 being the feedback element. What I can offer is that adding the varicap circuit shown in the second circuit the feedback portion is greatly disrupted. Note that neither end of the tuned circuit is near ground potential and so it is not a good candidate for changing to varicap tuning. For that to be possible you need a circuit with one end of the tuned circuit grounded..
hello, just to ground one wire from tuned to ground and that is? thnx mannn...;-)
do you mean R2?OK, so move the end of the 230K resistor up to the base of Q1, and then move the 100Nf capacitor to between the base of Q1 and the top of the tuned circuit. Next ground the tuned circuit. NOW you can substitute the varicap diode for the tuning capacitor, and if the tuned circuit happens to resonate at the frequency of some radio station you may hear it. That is, if the signal is strong enough to drive one of the amplifier stages into non-linear operation. Otherwise yo will indeed need a detector, which the easy kind is a diode and then a small filter capacitor. Use the posted detector circuit, it should work.
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.do you mean R2?
by Jake Hertz
by Jake Hertz
by Duane Benson
by Duane Benson