I chose the 1.86 MHz crystal because I stumbled upon a pile of them at a surplus shop. I can supply them for a while.
“Introducing Microcontrollers To Your Amateur Radio Club” The January-February 2010 issue of TCA (pages 43-47) featured the article “Introducing Microcontrollers To Your Amateur Radio Club” by Dave Green, VE3TLY, David Conn, VE3KL and Mike Kelly,