Milt, W8NUE and
Frank at the bottom "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)." Yea that makes since. I was thinking that maybe I could reach a threshold level of rf input but that sounded complicated. Well maybe not since this would mean amplification ahead of the AND gates. I guess the only really simple QSD would be to use TUF 1 or SPL 1 mixers. "(Of course this is an idealized description of the QSD switches)." Curious? Maybe the simple thing I do have here is the 74HC74 splitter which is commonly used. I am looking more into Quad Bilateral Switches now since they are actually simple to use. DIP and surface mount. And I will look at Quad Analog Switches to see what they can do? I am not sure, but in looking at the internal circuits of the IC you can get a clue as to whether you can use it, if the bandwidth is high enough in HF. And anything that operates as a "linear device" as you say Milt, is then a good candidate. * * * * * * * * * * * * * * Frank: Your email must have stripped the schematic, I got it here in my email. Here is the link: http://f1.grp.yahoofs.com/v1/IDDSRpy6q3UubvPEuFlrn58zMsDm3cAfTDU9VcSkw2QOFfQ5C_jTvkDnJwIAXtsbvqwWSixAqbHOEZcR9DrqNKnR-Fc/KA9RZA/AND%20Gate%20QSD.gif The circuit diagram is also at the group in the starter post of this topic: http://groups.yahoo.com/group/soft_radio/message/2693 Dan
