> --- In [email protected], "Daniel Jackson" <[EMAIL PROTECTED]> wrote: > >> This may be too simple to work right. >> >> Yet, the way digital circuits mix frequencies it appears to be possible. >> Only thing I have Flip Flops but no AND Gates to try this now. >> >> Anyways the LO IN is phase shifted with a 74HC74 Dual D Flip Flop and >> the QSD section is merely a Dual AND Gate IC. >> >> What do you think? >> Impossible? 5 >> 0/50 chance? >> >> Dan,
Yes, it is way too simple. First, the AND gate is not a linear device. It's output is a logic level (0 or 1). The switches that are used are "linear" devices. The output is linearly related to the RF/IF input, but multiplied by a square wave whose amplitude takes on only the values 0 and 1. This means that the output of the QSD switches can vary in amplitude from 0 to +/- the amplitude of the RF/IF signal, and will be constant at 0 when the switch is OFF. (Of course this is an idealized description of the QSD switches). Milt, W8NUE
