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

[Donald Tillman]

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

--
Don Tillman
Palo Alto, California
don at till.com
http://www.till.com