If your transistor base is not getting the 5v, then you are not going to get the needed results.
Are you getting the needed results with 5V on the base? Do you realize the 5V V BE is the Absolute Maximum Rating of the 2SC5200 transistor ? It is a very bad thing to operate any transistor at the limit of its Absolute Maximum Rating. Look what happens to the base current above 0.6V: So, try to get the 5v on there, and it should work.
What do you mean by "work" ? If you mean pulsing the coil with the maximum possible current by saturating the BJT 24,000 times pers second, then there are much better ways of doing that, ...especially by not using a BJT at all ! i.e. using an IGBT or N-ch MOSFET instead of the BJT because they are faster, cooler, require less drive current and generally can handle larger drain currents faster. Anyway, below is a simpler method that still uses the BJT in pulsed saturated mode: Like Vasik mentioned, the higher the voltage, the higher is the output. Lower voltage, lower output.
I think he meant V CE, not V BE. I doubt that the antenna signal has anything to do with it.
You seem awfully sure about that. Consider that using a BJT to pulse a coil instead of a IGBT or MOSFET does not make much sense. IGBTs and MOSFETs are faster, cooler, require less drive current and generally can switch larger drain currents faster and are easier to control. BJT makes sense only as a linear amplifier. If this is true then it means that the Q3/Q4/Q5 circuit only works to bias and gate this linear amplifier. If you are wrong, you are missing a very important mode of operation, namely the amplified feedback of the MHz signal from the antenna. The antenna is supposed to have some function - doesn't it ?
« Last Edit: 2021-06-13, 23:17:54 by verpies »
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