On Mar 18, 2022, at 12:27 PM, Tom Lee <[email protected]> wrote:A mixer has one input (the LO) fixed.That’s my last post on this subject. In my career, I’ve found teaching much less challenging than “unteaching” someone who has dug in his heels with a dogmatic position.CheersTomSent from my iThing; please forgive the typos and brevityOn Mar 18, 2022, at 04:42, Bob kb8tq <[email protected]> wrote:HiIf you fix one of the inputs then you violate the basic definition.You then get a *different* definition of linearity that is not the sameas the original definition.BobOn Mar 17, 2022, at 9:43 PM, Tom Lee <[email protected]> wrote:Ok, now really look at what you wrote. If you were to double A, leaving B (the LO) fixed, what happens to the output?
-- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 http://www-smirc.stanford.eduOn 3/17/2022 18:38, Bob kb8tq wrote:
Hi The output is A multiplied by B, that does not meet the definition of a constant times any input, BobOn Mar 17, 2022, at 9:21 PM, Tom Lee <[email protected]> wrote: Bob, Show me that a multiplier, as used as a mixer, fails to meet your defnition. --Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 http://www-smirc.stanford.edu On 3/17/2022 18:12, Bob kb8tq wrote:Hi At least when I took the course in school on this stuff, the basic definition of “linear” was indeed that the output was the input times a constant. Anything other than that was “non-linear”. This is at the root of the conversation about mixers being non-linear. If that *is* you definition of linear then mixers must be non-linear. BobOn Mar 17, 2022, at 9:09 PM, Tom Lee <[email protected]> wrote: Think about how one actualy uses a multiplier as a mixer, Bob. The input-output relationship of relevance is that between the IF output and the RF input. That is supposed to be linear, right? That is, the output should be a constant times the input, just as you yourself stated as the requirement. --Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 http://www-smirc.stanford.edu On 3/17/2022 17:45, Bob kb8tq wrote:Hi If you accept the definition that a “linear” circuit *only* produces the input times some constant ( = the gain ) then anything that multiplies must be non-linear. If you look at a different definition, then of course, they can be linear. It’s just a mater of what your base definitions are. BobOn Mar 17, 2022, at 8:13 PM, Tom Lee <[email protected]> wrote: (Just to clarify, this was posted in response to Bob Nickels, not to Mike St. Angelo -- sorry for the confusion, Mike!) --Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 http://www-smirc.stanford.edu On 3/17/2022 12:16, Tom Lee wrote:I wish people would stop repeating the claim that mixers are inherently nonlinear. That’s completely false. It is true that nonlinear things can produce mixing, but that’s a side effect, not an inherent property! Good mixers have to be linear. You want the IF output to be proportional to the RF input. We treat mixer nonlinearity in much the same way as we treat amplifier nonlinearity. It is an undesirable property and considerable effort is expended to minimize it. Tom Sent from my iThing; please forgive the typos and brevityOn Mar 17, 2022, at 11:39, MICHAEL ST ANGELO <[email protected]> wrote: Bob, Enjoyed that article and the one about the Si5351 Quadrature oscillator. Have the tried feeding the Si5351 to the SA612 instead of an Epson? It gives the the ability of easily changing frequency. The SA612 and Si5351, what a pair for experimenters. Mike N2MSOn 03/17/2022 1:05 PM Robert Nickels <[email protected]> wrote:On 3/17/2022 11:10 AM, Phillip Carpenter wrote: Can you please share the circuit diagram of your universal converter board that you used with the BC-453 receiver?I've added an article about it to my website: https://tinyurl.com/mrj7rndd The 4.7uH/100pF values shown work for 40 meters, or calculate your own - I use a 10uH fixed inductor and 150-180pf capacitor for 75-80 meters. 73, Bob W9RAN______________________________________________________________ ARC5 mailing list Home: http://mailman.qth.net/mailman/listinfo/arc5 Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: https://www.qsl.net/donate.html______________________________________________________________ ARC5 mailing list Home: http://mailman.qth.net/mailman/listinfo/arc5 Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: https://www.qsl.net/donate.html