As an analog, HDR, discrete component, radical homebrew fundamentalist, obviously I have been concerned about all the hype about SDR.  SDR advocates often make it sound as if those of us who build with discrete analog components (crystal filters!) are hopless troglodytes, about to be thrown on the ash heap of radio history.  Or something like that.  They sort of imply that without the cleansing benefits of SDR, our signals will remain hoplessly dirty. 

I find it interesting that Sherwood concluded that the cleanest transmitter he ever owned was a Collins 32S-3!  He compared the two tone output of this old rig to that of a modern transceiver.  This was in 2019.  See above.  HDR wins. 

Don't get me wrong.  I want to clean up the signals from my HDR rigs.  But I am encouraged by Sherwood's remarks.  I do not think I will have to go SDR in order to have a clean signal.   I may just  do some two-tone tests on the rigs,  make some adjustments, and maybe build a class A Thermatron .1 kW linear. 

Mike WU2D put out this nice video (above) about whether or not he should part out his Heath SG-6 signal generator, using the parts in a Paraset construction project.  I faced a similar question years ago: 

https://soldersmoke.blogspot.com/search?q=SG-6

I just solid stated the SG-6.  I was influenced by Farhan and the drinking straws that he picked up with his kids at a McDonalds in Hyderabad. 

As with the QF-1, I say to Mike: GO FOR IT OM!  You need those parts for other projects.  Don't feel bad about the SG-6.  But keep that switched coil assembly -- it is quite useful. 

Dean KK4DAS asked me why we have these switches on our 'scopes.  I didn't know.  Dean asked Alan Wolke W2AEW.  Alan knew: 

Alan Wolke wrote: 

Interesting background on the 20MHz vertical BW selection. This feature has existed on the vast majority of all oscilloscopes since the 50s or 60s (both analog & digital). When I explored the history of this, I spoke to some of the folks at VintageTek.org, and wound up having a chat with THE engineer that did it first!  Tt was John Addis, designer at Tektronix. 

The main reasons you'd use this filter would be to improve the signal to noise ratio (SNR) for signals when their frequency content is below 20MHz.   You've probably noticed that, even without any signal connected, the thickness of the trace is thinner when you engage the 20MHz filter. 

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Alan sent a link to a Wiki page about the 7A11 that John Addis was designing.  Alan says this places the initial inclusion of the 20 MHz BW Limit filter to the mid 1960s: 

https://w140.com/tekwiki/wiki/7A11. 

Thanks Dean, thanks Alan!