--- In [email protected], "Lyle Koehler, K0LR" <[EMAIL PROTECTED]> wrote: > Lyle, that makes allot sense, having a point of reference in the spectrum which the LO IN provides. So we can dismiss that idea.
I guess the circuit might be better used for a balance meter of some sort, which is what the idea seems better suited for. Dan > --- In [email protected], "Daniel Jackson" <wavelengths@> > wrote: > > > > The Ways: > > > > There are two ways we use in radio to take the baseband audio off of > > a signal carrier. > > > > 1. The beat frequency mixer method such as is used with Sideband > > and in the Quadrature demodulator ideas. > > > > 2. The audio is demodulated off of the RF signal carrier from the > > i.f. by means of a diode. Where the diode is not being used as a > > mixer but rectifier. Keep this one in mind now..... > > In method 1, if we know the local oscillator frequency, the beat > frequency tells us how far a signal is above or below the local > oscillator. With the help of the I and Q signals, the SDR software can > determine whether the signal was above or below the LO. So if there > are multiple frequencies present, the software can sort them all out. > > To see what happens with method 2, take the simplest case of a > constant carrier signal. The output of each diode detector (I and Q)is > a DC voltage. There is no way to determine the frequency or phase of > the signal. If multiple frequencies are present, the detector outputs > will be a DC component plus a mishmash of all the mixing products > between the various frequency components. Simply put, method 2 won't > work... > > Lyle, K0LR >
