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. 

Here is a good (and very recent) article on IMD ("splatter") produced in transmitters. The focus is on VHF, but much of this is relevant to HF operators.  I found the footnotes on the ARRL "Clean Signal Initiative" to be worrisome.  They seem to just be assuming that all ham operators will be using commercial gear, and the "OEM" needs to be made to meet certain standards. This seems to leave the homebrewer out in the cold.  I can see where someday soon, the "standards" will exceed the capability of analog homebrewers.  That would be bad.  

The role that signal strength plays in the perception of "splatter" is often misunderstood by the "waterfall police."  We often we hear some irate waterfall policeman screaming that,  "You are 40 over and far too wide."   Here is a good quote from the article on this point: 

"If you have a calibrated spectrum display (as many SDR’s are these days), you can directly measure the level difference in dB. If it is 30 dB or more, then it could be an acceptably “clean signal”, even if it is bothersome. Most ham voice communication is conducted with less than 30 dB signal/noise, and in that case the unwanted IMD is buried in the noise."

And even in a low noise environment,  if the signal is 40 db over S9. that would mean the signal PEP is at -33dbm.  If the IMD products are 46 db down from the signal peak, that means your IMD products are -79 dbm.  That is S-8!   That signal will look quite wide in the waterfall, but it would be within FCC specs, right? The problem here is not so much distortion, as signal strength.  And let's remember that "legal limit" is usually a misnomer:  FCC regs require hams to use the minimum power necessary, not 1.5 kW on every single QSO. 

https://www.youtube.com/watch?v=lNypq1XuZRo

Really interesting.  Why the design of the analog portions of chips is so much harder than the design of the digital portions.  

Great channel. 

I found the comment about Sony's belief that NPN transistors are superior to PNP very interesting. 

 

https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/hr/1988/10/page71/index.html

 

I give it FIVE Soldering Irons! 

I found it on Amazon Prime.  The workshop scenes remind me of ham workshops.  The movie character Harry Caul was based on real-life Marty Kaiser.  Was Marty a ham? 

POSTSCRIPT (August 23, 2024):  Yes, he is a ham!   W3VCG!   FB.  Here is his web site: 

http://www.martykaiser.com/fbi1~1.htm

https://en.wikipedia.org/wiki/The_Conversation

http://www.martykaiser.com/odyssey2.htm

Thanks to Roy WN3F for reminding me to watch this film.  Roy found a clip that is reminiscent of hamfests: https://www.youtube.com/watch?v=joM5VDCIQg8

 29 July 2024