[RTTY] Dash vs. space

[Rudy Bakalov]

I find Chen's lessons on the sound science behind RTTY very refreshing and very often there is something new I learn from them. The latest one is his analysis of using a dash between to separate 599 and the exchange(s):

http://lists.contesting.com/pipermail/rtty/2013-February/038940.html


Long time ago I did my own probability analysis, mostly driven by the desire to decide if I want to get a Canadian call sign instead of using /VE3, and concluded that I have to keep the transmissions as brief as possible.

So this CQ WPX weekend I decided to see what happens when I switch the space to a dash. I did so on the 20 m path to Japan as I wanted to see what happens when the signal is distorted by significant flutter. As the rate was low the possibility of more repeats was not a concern.  Running about 800W into a 5 el tribander @ 100'

In over 2 hours I did not have to repeat my exchange even once. I decided to keep the dashes and then went to 40m and 80m and for the next 7 hours I had to repeat my exchange only a few times, mostly to barely audible stations on the West Coast and Asiatic Russia. EU rate was as usual. Running a 4 el 40m yagi @ 90' and a 80m inv-V @ 85'


This could be due to the placebo effect, but I perceived an increased use of dashes by other stations. Interestingly, I did not have any problem copying such stations; in fact, I did not ask a single station using dashes for a repeat.

One point to note is that I use 4 concurrent decoder windows with 2 MMTTY profiles and 2 instances of 2-Tone, one with the regular and the other with the flutter profile. The salient point here is that I don't have to switch between profiles and can observe the quality of the copy consistently over a long period of time using different decoders.

So, is this is robust scientific experiment? No, but the empirical data gives us a good reason to pause and re-think old strategies.

Rudy N2WQ