[GreenKeys] Christmas Question From KD6EMW

[Russmill47 at aol.com]

Hi Jan,
 
You can pull a crystal lower in frequency by adding capacitance.  In  the 
case of frequency shift keying, the standard convention is to shift lower  when 
going from the mark frequency to the space frequency.
 
So, if I type nothing, I stay at mark frequency.   When a type  any 
character, I go:  start pulse, data bits 1-5, stop pulse - back and  forth from mark to 
space to mark, etc.
 
Since I go lower in frequency to space, I simply switch in a small amount  of 
capacitance - maybe 1 - 7 picofarads (pf) to shift 170 Hz.
 
In the very old days -- before the 1970's -- and before 170 shift became  
preferred, hams were using 850 Hz shift.
 
73,
 
Russ
WA3FRP