At 16Hz Xc of C1, C2 is 995,000 Ohms or 995k Ohms.

@radio_electronics4047

2 жыл бұрын

Oh my bad, you are absolutely right. Thanks for this comment! It is not possible to add text boxes to videos anymore, but I will write it in the description.

@ArshaansEdits

Жыл бұрын

@@radio_electronics4047 C2, c3 and 10k got to the ground ryt?

@radio_electronics4047

Жыл бұрын

@@ArshaansEdits Yes, C2, C3, and R1 (with 10k ohms) are connected to ground.

@deang5622

11 ай бұрын

And you referred to it in the video as resistance, which it is not, it is reactance. A capacitor does have a small amount of resistance, a parasitic unwanted resistance called ESR - equivalent series resistance.

Yes, the circuit is a VCO (voltage controlled oscillator) and the capacitance of Cbe or Ceb, call it what u want, is given by the formula: Cpi = Cje + gm*Tf Cje and Tf its a variable that comes from transistor technology Silicon design of the transistor, dimensions, etc.. (its on the datasheet). You can see that gm = ibias / Vt Where Vt = Thermal Voltage = ~25mV. So the feedback network of this circuit would be between C5 and Cpi. where Vin = Xcpi * Vout / (Xcpi + Xc5) Vout = Voltage @ colector Vin = Voltage @ emitter Because at ressonance Vout = Voltage @ Capacitor 5 (because paralel L and C impedance goes to infinity). The analysis of this circuit is deeper than the guy on the video explained, but thanks for making this kind of content!! A tip for working with oscilators and determining (predict) voltage of oscilation is: 1) Say that Voscilation = Voltage YOU define. 2) Say that Vin = Vcollector after goin thrught Capacitive divider C5 >> Cpi (parasitic capacitance of transistor)! 3) Based on Vin = cap_divider * Vout, determine Gm(Vin) "Large Signal Transconductance" which is expressed by gm * Bessel(Vin / Vt) / (Vin/Vt) 4) Work out the amplifier topology gain, based on your Gm(Vin) (already obtained) and the gain of a common base topology. 5) Choose bias point, etc that works out for you. So that the NEGATIVE impedance REAL and IMAGINARY parts cancel out. (The transistor Common Base - C.B. amplifier can be seen as a negative impedance.. and the feedback network / antenna Transmission Resistance ~35 ohms for a 1/4 wave antenna is the other impedance. 6) Im { Zcommonbase @ collector } = - Im {Load} (in this case the antenna + inductor) 7) Re { Zcommonbase @ collector } = - Re{Load} This is the real math etc on how you do it. You have to understand: - Large signals transconductance - How to do the math for the CB amplifier impedance @ collector without load. (you can use a circuit simulator.. to know it and bias it ez) - LC parallel impedance = Infinity @ Fressonance - For STABLE oscillation you NEED Im { active circuit } = - Im { load } AND Re { active circuit } = - Re { load} That's it.. I can't really explain it all in a comment but this is the real deal. Also this circuit is a VCO (voltage controlled oscillator) so for creating a VCO you NEED a LC tank circuit that CHANGES its values with a VOLTAGE, so that's why Cpi (parasitic base capacitance) is a MAJOR part of the LC tank circuit (its just not there because its a parasitic from the transistor between base and emitter).

@VitorFThome

Жыл бұрын

Cpi parasitic capacitance = Cje + gm*Tf gm = ibias / Vt When you change Vb of transistor, since Vbe = 0.7 = Constant >>>> i_bias changes, so "gm" changes and "Cpi" changes as well!! That's how a voltage signal modulates the FREQUENCY of oscillation. Because Cpi is part of LC tank ! And the LC tank defines oscilating frequency.

@VitorFThome

Жыл бұрын

You CAN also do the maths for the barkhausen criterion which is another way to get stable oscillation. Similar to the negative resistance technique. But in that method you use: Loop gain = 1 (total gain of the circuit) Which is = L = Alfa * Beta Where alfa = cap divider = vout/vin Where beta = gain of C.B. Amp = Gm *ro After that you must also ensure phase of loop (Alfa * beta phase) is zero or multiple of 2*pi so that the feedback is positive and the signal gets bigger and bigger. In real design you use loop gain of 1.2 or 1.5 because Gm(Vin) Will limit gain and stabilize it in 1 if signal grows too much.

@abhishekgadekar5618

Жыл бұрын

​@@VitorFThome thank you so much for the detailed explanation

@VitorFThome

Жыл бұрын

@@abhishekgadekar5618 we have to help each other in electronics is such a hard field and people never post the good stuff online there is also a lot of misinformation. Very different from the programming field that I use to work with nowadays.

@lawrencejelsma8118

Жыл бұрын

​@@VitorFThome... If you are privvy (assuming no chips used to hide the circuitry ... but IC schematics available) to the converter technologies of used old electronics such as 2007's converter boxes output to be input to analog TVs you can get an idea of real world components, despite transistors having characteristics that change components such as a stand alone transistor to the transistors in an IC chip. This design helps to configure a really basic transmitter as is all other transmitters figured out in many complete electronics for technicians books ... found here and there for this 1960-70s electronics working today.

Cool info, thanks for sharing, well done :)

the collector- base capacitance changes with the applied base voltage hence changes the resonant frequency, resulting in frequency modulation

As the collector voltage swings due to audio signals, the internal capacitance of the reverse biased transistor (CB junction) varies and that causes the RF frequency change as per audio which is called frequency modulation.

FM - frequency modulation. You have completely failed to explain how the carrier signal is frequency modulated by the audio signal.

I think, not sure about that,..R1and R2 are the biasing resistor, so C1 and R1 act as the Highpass filter, c5 acts as the bypass for rf signals to ground, and c3 acts as the bypass for RF so they don't disrupt the power supply.. Is what I think 😊... correction please 🤗

0:36 Why is that resistor necessary? The capacitor will continue to block DC even once it is fully charged.

if I use a better amplification circuit and add an antenna instead of the speaker output, Would it give better range?

@radio_electronics4047

Жыл бұрын

Where do you see a speaker output? I use an fm antenna. Im not sure how to increase the range, probably more stages of amplification, more transistors, more power, but I don't think it's that simple.

@ArshaansEdits

Жыл бұрын

@@radio_electronics4047 I mean after the Amplification circuit instead of using a speaker for common amplifier can I give that output to the transistor?

@lawrencejelsma8118

Жыл бұрын

​@@radio_electronics4047... I agree ... Other FM transmitter circuits are in other technician electronics books showing how VCRs or Digital Converter boxes of 2007 readied the audio part for TVs vs an antenna design. Those using IC chips to transmit their conversion have chips used schematics ... Very more components abstract to this simple design (that comes from the 1960s or 1970s hobbyists enthusiastic circuits)!! Great video for a nice quick low parts used transmitter for a small sound from a microphone video! 👏

Hi, I think C4 should be connected to positive of the power supply instead of negative and it should be a variable capacitor to control the transmitting frequency.

@SpeccyMan

Жыл бұрын

You think incorrectly - it connects to ground! However, you are correct that it could be replaced with a trimmer but connected to ground.

@clementdelafontaine9145

Жыл бұрын

@@SpeccyMan I'd agree with a connection to 9V node, why to ground? Does it even make any difference since in small signal analysis, ground and power supply are seen as connected.

@kahenajr2515

3 ай бұрын

I think if you connect to the positive it will work (but as the parallel lc oscillator) I tried this and worked out..

does the transistor here acts both for amplification and maintaining the frequency oscillation?

@radio_electronics4047

2 жыл бұрын

Yes, it keeps the oscillation going and amplifies the audio signal. Everytime there is a positive voltage from the audio signal it "nudges" the oscillation.

@pradeszebua

2 жыл бұрын

@@radio_electronics4047 what's the drawback tho? I'm assuming using two transistors, one for the oscillation and one for the amplification will be better...

@radio_electronics4047

2 жыл бұрын

@@pradeszebua The sound that comes from the smartphone is already amplified and you could just hook it up to speakers and would hear it fine. So I don't think the amplification part plays an important role here, but I'm not an EE so I can't give you a really qualified answer on that.

@pradeszebua

2 жыл бұрын

Ah I see, thanks man

hello I want to ask about something very interesting why in internet I find the same circuit (like this in the video) for the am and fm waves and the fm wave should be completely different between the am wave so why this? I think the radio can receive the am and fm waves it request just the frequency? I'm not sure plzzzzz answer!

@radio_electronics4047

Жыл бұрын

If you use a bigger coil and caps with more capacity and use a very large antenna it might also work for AM, but I have not tested this.

@AlaaAchemaoui

Жыл бұрын

​@@radio_electronics4047 sorry but I mean the FM radio can receive a AM wave has the FM band but the receiving way is completely different so how can it be possible to a FM radio receive a AM wave?

I'm sorry. I don't understand why 1 in the formula of reactance is negative?

Why is C1 in reverse? Will the audio current even flow this way?

@radio_electronics4047

Жыл бұрын

The polarization should not matter. C1 is just for filtering out the DC from the audio signal. You could probably use an unpolarized cap, but bigger caps from 1µF on up are usually electrolytics.

@medicallyunexplainedsymptoms

Жыл бұрын

C1 isn't reversed. The base of Q1 is biased at about 2.4V and the audio signal is likely to be centred at 0V. The + terminal of C1 is at the more positive voltage.

My criticism is the robotic narrative, complete with irregular pauses and serious mispronunciations! It is hardly surprising, given the poor grammar in the video description. I'm trying to explain how the circuit works and the use of every component. (Corrected version of your 4th sentence, so it doesn't end with a preposition!)

@clementdelafontaine9145

Жыл бұрын

At least this guy attempted to share knowledge, not everybody takes time to do so.

WTF

Every wireless transmission except CB is penal and if you are detected you pay a fine. But the authorities remove all your electronic up to the screwdriver, think about!