Sorry for the cryptic title; this is inspired by another thread here, about trying to listen to high-frequency signals normally out of auditory range. (For instance, bringing the HF components of a lightning strike down to the audio spectrum.)
So what if a guy were to build something like this:
**broken link removed**
Let's say the HF ranges of interest are somewhere in the 300 kHz-2 mHz region, with a few switchable notches on the oscillator. The low-pass filter would limit the signal to the audio range, rejecting the upper frequency from the mixer.
Not sure how the mixer would work. What if you just combined the two signals (wired together): wouldn't that produce the sum and difference frequencies? or do you need an active mixer stage here?
In any case, if anyone could come up with a quick first-pass circuit for this, that would be nice.
So what if a guy were to build something like this:
**broken link removed**
Let's say the HF ranges of interest are somewhere in the 300 kHz-2 mHz region, with a few switchable notches on the oscillator. The low-pass filter would limit the signal to the audio range, rejecting the upper frequency from the mixer.
Not sure how the mixer would work. What if you just combined the two signals (wired together): wouldn't that produce the sum and difference frequencies? or do you need an active mixer stage here?
In any case, if anyone could come up with a quick first-pass circuit for this, that would be nice.