Why USB versus LSB on 20 meters and above ?, let's ask the AI

 I tried using the Bing search engine AI to ask about why the low bands use LSB and the high bands use USB.

The answer references two pages for technical reasons why:

http://www.redwaveradio.com/11_4d1c8dd3748ce22d_1.htm

"The ham radio practice came about because of a particular military
surplus radio that when added to a carrier generator produced
USB over 10 mHz and when subtracted LSB below it."

https://www.mdarc.org/operating-aids/lsb-or-usb

"It's a historical oddity. Early amateur SSB rigs used a 9 MHz IF system, and it was easier and cheaper to generate LSB below 9 MHz and USB above 9 MHz.

You will notice that on 160, 80 and 40 meters, LSB is mostly used and on the higher frequency bands, USB is used. This is a leftover from the early days of SSB when radios were designed a certain way, when SSB was in its infancy."

So basically AI doesn't know the reason either :)

The first reference seems plausible but no details - this wasn't documented in QST that I've ever seen

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm