Your presumption that the keyer built into the ExpertSDR2 1.3.1 update8 SunSDR2 DX Linux is using CURTIS A MODE is definitely wrong. It is MODE B. I was wrong in my previous statement that this is mode A because I reproduced Roman’s comment before my SunSDR2 DX arrived. Putting my SunSDR2 DX onto air confirmed that it is definitely mode B! TNX SM5IMO for notice!
There are many reasons for use of an external keyer. It can be the ULTIMATIC MODE, see la3za.blogspot.com/2013/05/is-ultimatic-morse-keyer-really-that.html
or many other references on the Net. Another good reason is keyer interaction with particular program, ie. Autosend option in TR4W or just the simple fact that the user is well accustomed
to his keyer used for years. Anyway, the external keyer complicates the way to (almost) perfect keying but has some advantages why the user prefers it and refuses to use the internal keyer.
Warning – the quite new TCI protocol would need years to cover all the subtle nuances of operating techniques. Although it is full of great new ideas, it can’t turn back to the years proven techniques which became domestic among DXers and contesters. Even full implementation of all 3 modes (Curtis A, Curtis B and Ultimatic) would not eliminate the need of an external keyer under particular circumstances.
I would urge to minimize the latencies! To be in proper picture, a latency of units of milliseconds can be acceptable however 10 ms and more is TOO LONG!
This article is a stub. You can help by expanding it providing more/new ideas and suggestions. Don’t hesitate to borrow a good idea from an older proven radio.