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I've got an idea for a receiver project, it's not commercial, just as a hobby....
Part of the idea needs a single LC tuned circuit to work at maximum 'Q'. The frequency would be around 150MHz but it has to be tunable say +/- 10MHz using a varactor diode. What I would ideally do is show the tuned frequency on an LCD display but a superhet with local oscillator and PLL is not an option. The idea is to use a microcontroller to produce a PWM signal which would then be filtered to produce a tuning voltage for the varactor, this sets the frequency. A 'Q multiplier' is built around the tuned circuit and under voltage control from the micro, the feedback is increased for just a few cycles to allow it to oscillate so the frequency can be measured. The rest of the time the voltage is set to just below oscillation point so highest Q is achieved. The PWM would be adjusted to maintain the desired tuning based on the frequency that was measured.
Has anyone tried this?
Brian.
Part of the idea needs a single LC tuned circuit to work at maximum 'Q'. The frequency would be around 150MHz but it has to be tunable say +/- 10MHz using a varactor diode. What I would ideally do is show the tuned frequency on an LCD display but a superhet with local oscillator and PLL is not an option. The idea is to use a microcontroller to produce a PWM signal which would then be filtered to produce a tuning voltage for the varactor, this sets the frequency. A 'Q multiplier' is built around the tuned circuit and under voltage control from the micro, the feedback is increased for just a few cycles to allow it to oscillate so the frequency can be measured. The rest of the time the voltage is set to just below oscillation point so highest Q is achieved. The PWM would be adjusted to maintain the desired tuning based on the frequency that was measured.
Has anyone tried this?
Brian.