[GreenKeys] Re: Just a few RTTY basic questions and a holiday thanks to all

[Russmill47 at aol.com]

John,
 
Have you checked your Model 19 to see how many points of range your machine  
does have?
 
You should have 80 point of range for a properly adjusted machine. If you  
haven't run this test yet (it may be covered in the books you already have  
received), run this test.  If you can't find this reference, send me a note  and 
I'll post the process.
 
The reason that a 45.45 baud machine can copy a 50 baud signal by  
misadjusting the range selector to the lower end of the range:
 
There are three types of data transmitted in a character (a printed  
character, lrts, figs, cr, lf, etc.):
 
Start pulse  -  in both 45.45 and 50 baud transmissions, the  pulse length is 
20 milliseconds.
Data pulses - in both 45.45 and 50 baud transmissions, each of the five  data 
pulses are also 20 milliseconds in length.
Stop Pulse - here is where the difference occurs!  In 45.45 baud  
transmissions, the stop pulse length is increased to 32 milliseconds. In 50 baud  
transmissions, the stop pulse is also 20 milliseconds -- just like all of the  other 
pulses.  
 
When you lower, and misadjust the range selector on your Model 19, you are  
compensating for the shorter stop pulse length.  
 
I've done this with Model 19s that I've had in the past as well as my  
current Model 28.
 
I hope this detail and the recommended test will give you the information  
you need to accurately copy the 50 baud signals that you will find on the  air.
 
73,
 
Russ
WA3FRP