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Ah it'll go into thermal runaway.With a brand new 9V battery, Q3 in my FM transmitter draws about 50mA and dissipates 0.45W which makes it warm.
Q3 might fry with a 12V or 13.8V supply even if the value of its base resistor is increased.
A 2N2222A has different capacitance than a 2N3904 but should work. Try it.BTW can I use 2N2222A for the 2N3904's coz i got a bunch of 2N2222A lying around at home.
What you mean by adding a heat sink? the 2n3386 got a built in heat sink doesn't?
Do you replace both Q2 and Q3 with it or just Q3?
A 2N2222A has different capacitance than a 2N3904 but should work. Try it.
But the frequency might not be in the FM broadcast band without changing the coils.
Like this I mean:**broken link removed**
A more efficient solution would be to bias the transistor in class C so it doesn't dissipate quite so much power.
That's true.Q3 will operate in class-C if the 47k base resistor connects to ground instead of to +9V.
That's because the duty cycle would be very low. My circuit will give a duty cycle of just under 50%.I simulated it with a 12V supply and the output power became 0.09 times the power when it was the original circuit with a 9V supply.
Well removing R8 would do that but the duty cycle will be low.
Here's how I'd do it.
The transistor is baised just below the point where it turns on and stays biased in this manner regardless of the power supply voltage.
You'll need more filtering on the output otherwise it will be littered with harmonics and interfere with other stations.
Q3 will operate in class-C if the 47k base resistor connects to ground instead of to +9V. I simulated it with a 12V supply and the output power became 0.09 times the power when it was the original circuit with a 9V supply.
Yes, I've seen that schematic on the Internet before.
It will work but needs a fairly strong input signal.
It could be connected to the output of the origional mod 4 transmitter.
I use LTSpice; most people do around here.
Yes, use the air coils and calculate their dimensions using the inductance formula.
The frequencies will be slightly lower due to the parasitic capacitance.