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No.The 1N914 is a common Silicone diode. It is in very similar to the 1N4148
D1 simply biases Q3. It doesn't clamp anything.D1 is used to clamp the drive to the buffer transistor to prevent overdrive that could either pop the transistor or cause it to overdrive and produce unwanted harmonics.
There is no audio filtering. Noise on the supply goes directly to the microphone through R1 and to the preamp transistor Q1 through R2.I personally think it's not a bad design. Plenty of filtering design to take into account unwanted harmonics.
the 1N914 the OP is referring to is D1, not D2. D1 biases the base of Q3 at 0.7V. a germanium diode here would not work, since it's forward voltage would only be around 0.3V. it's a rather ingenious method of providing bias since it eliminates the typical resistor divider that would load down the tuned circuit (C6-L1)
I don't see an RF oscillator. Do you?
I see the simple oscillator when I turn the upside-down PNP transistor right-side up.Isn't Q2 RF oscillator, C7 feedback and L1-C6 tuned circuit?
This is same (although using PNP transistor) as most oscillators in hobby FM transmitters.
Look at D1, I've never seen such kind of diode in oscillator of FM Tx. For why it is used here? Is it equivalent of 1N4148 germenium diode or like 1n5711 t?
Thanks
D1 simply biases Q3. It doesn't clamp anything.
Yes.this circuit is not drawn in a conventional and that makes it a bit awkward to follow...