Rick N3FJZ's Early Completion of the SolderSmoke Direct Conversion Receiver Challenge

 It was a cold day in early February 2023.  Rick N3FJZ had responded to an early version of the SolderSmoke Direct Conversion Challenge: 

I wrote: 

Rick N3FJZ has completed his the direct conversion receiver that we will soon be building with students at a local high school.   See video above. 

We are hoping that a number of people will build the receiver as we designed it.  Some folks have sent us versions of the receiver that they have built, but these versions often include significant deviations from our design, rendering them less-than-useful in checking our work.  Rick built it just as we prescribed.  His build is very useful in confirming the validity of our design.  So if you are working on one of these receivers, I would encourage you to -- for the moment -- dispense with innovations and build it the way Rick did:  as per the design we have been using. 

We know that our design is not perfect.  But we have decided to stick with it because it is very simple and very easy to explain.  Examples:  We know there is an impedance mismatch between the mixer and the AF amp.  But fixing this would introduce complexity that we want to avoid.   And the receiver works fine with the imperfection.   We know that a push-pull AF amp would probably work better than the one we have.  But we do not want to have to explain push-pull amps, biasing schemes, and PNP transistors in this short introductory course.  So we stuck with three common-emitter AF amp circuits and an 1K-8ohm transformer. 

Rick did a really excellent job not only in building this receiver, but also in documenting it.   His diagrams and drawings are really superb.  We will probably use these in our presentations to the students: 

http://www.remmepark.com/circuit6040/SolderSmoke-DCR/SolderSmoke-DCR.html#AUDIO_AMP

We will keep all of you informed on the progress of this project.  We will begin this week.  But if you are still working on the receiver, please send us your work,  even if it comes in after we begin the course.  

Thanks Rick! 

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Thanks indeed Rick.  Sorry it took so long to put you in the SolderSmoke Challenge Hall of Fame, but you are in now, and you definitely deserve it.  Congratulations OM.  

I especially like your finding the audio ourput transformer in an old transistor radio.  Too often we see builders quit after discovering that Mouser or some other supplier no longer stocks the needed part.  You show that homebrewers have other sources available, if they are willing to scrounge a bit.  FB.    I also liked the switch that helped compare the outputs of the two AF transformers.  Very useful.  

Thanks too for all the great videos and your really nice documentation -- we have used your work quite a lot. 

73 and welcome to the Hall of Fame! 

Rick N3FJZ

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Documentation on Hackaday:

https://hackaday.io/project/190327-high-schoolers-build-a-radio-receiver

 

SolderSmoke YouTube channel:

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