[sdiy] On the topic of ring modulation (Using FETs instead of diodes?)

[gordonjcp at gjcp.net]

On Thu, Aug 14, 2014 at 02:20:04PM -0700, Donald Tillman wrote:
> 
> On Aug 14, 2014, at 1:30 PM, Donald Tillman <don at till.com> wrote:
> 
> > Radio Dude is demonstrating the radio application of a ring modulator, not the audio application.  In his case he's operating with the LO signal at about 6 times the level of the RF signal, so the bridge diodes are effectively being used as switches, switching the RF signal between polarities.
> 
> By the way, this is quite common in the radio world; instead of a simple multiply operation between two sine wave sources, to overdrive one of them and then have to go to the additional trouble of filtering out of the spurious frequency components, as this results in a lower overall noise figure.
> 
> And sure enough, the MC1496 data sheet also describes operation with one of the inputs overdriven.
> 
>   -- Don

It's also worth considering that in the Tayloe mixer you use analogue switches and a centre-tapped transformer to switch between 0° and 180°, and 90° and 270° outputs with a four-phase clock.

-- 
Gordonjcp MM0YEQ