June 23rd, 2013
How long does a particular bit of Morse code take to transmit at a certain speed? This is a simple question, but when sitting down trying to design schemes for 10-minute-window QRSS, it doesn't always have a quick and simple answer. Yeah, you could sit down and draw the pattern on paper and add-up the dots and dashes, but why do on paper what you can do in code? The following speaks for itself. I made the top line say my call sign in Morse code (AJ4VD), and the program does the rest. I now see that it takes 570 seconds to transmit AJ4VD at QRSS 10 speed (ten second dots), giving me 30 seconds of free time to kill.
Output of the following script, displaying info about "AJ4VD" (my call sign).
Here's the Python code I whipped-up to generate the results:
xmit=" .- .--- ....- ...- -.. " #callsign dot,dash,space,seq="_-","_---","_","" for c in xmit: if c==" ": seq+=space elif c==".": seq+=dot elif c=="-": seq+=dash print "QRSS sequence:n",seq,"n" for sec in [1,3,5,10,20,30,60]: tot=len(seq)*sec print "QRSS %02d: %d sec (%.01f min)"%(sec,tot,tot/60.0)
How ready am I to implement this in the microchip? Pretty darn close. I've got a surprisingly stable software-based time keeping solution running continuously executing a "tick()" function thanks to hardware interrupts. It was made easy thanks to Frank Zhao's AVR Timer Calculator. I could get it more exact by using a /1 prescaler instead of a /64, but this well within the range of acceptability so I'm calling it quits!
Output frequency is 1.0000210 Hz. That'll drift 2.59 sec/day. I'm cool with that.