I believe that audio high freq attenuation was responsible for an earlier change from 2550 Hz center to 2000 Hz center. The voice channel SSB rigs didn’t like 2975 as a high tone. 

But I don’t think that would have explained the change from mark-high to mark-low. 

Nick England K4NYW
www.navy-radio.com


On Fri, Mar 8, 2024 at 7:16 PM Dave Horsfall <dave@horsfall.org> wrote:

Perhaps it may have something to do with higher frequencies being
attenuated or something?

-- Dave (vk2kfu)______________________________________________________________
GreenKeys mailing list
Home: http://mailman.qth.net/mailman/listinfo/greenkeys
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:GreenKeys@mailman.qth.net

>>> Jordan Spencer Cunningham's GreenKeys Search Tool: https://teletype.net/gksearch
>>> 2002-to-present greenkeys archive: http://mailman.qth.net/pipermail/greenkeys/
>>> 1998-to-2001 greenkeys archive: http://mailman.qth.net/archive/greenkeys/greenkeys.html
>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool: http://comcents.com/tty/greenkeyssearch.html

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to navy.radio@gmail.com