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Calculate QRSS Transmission Time with Python

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.

program output

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.

Output frequency is 1.0000210 Hz. That’ll drift 2.59 sec/day. I’m cool with that.

About the author

Scott W Harden

Scott Harden has had a lifelong passion for computer programming and electrical engineering, and recently has become interested in its relationship with biomolecular sciences. He has run a personal website since he was 15, which has changed names from HardenTechnologies.com, to KnightHacker.com, to ScottIsHot.com, to its current SWHarden.com. Scott has been in college for 10 years, with 3 more years to go. He has an AA in Biology (Valencia College), BS in Cell Biology (Union University), MS in Molecular Biology and Microbiology (University of Central Florida), and is currently in a combined DMD (doctor of dental medicine) / PhD (neuroscience) program through the collaboration of the College of Dentistry and College of Medicine (Interdisciplinary Program in Biomedical Science, IDP) at the University of Florida in Gainesville, Florida. In his spare time Scott builds small electrical devices (with an emphasis on radio frequency) and enjoys writing cross-platform open-source software.

Permanent link to this article: http://www.SWHarden.com/blog/2013-06-23-calculate-qrss-transmission-time-with-python/

2 comments

  1. john

    Hi Scott,

    I have always wondered if ASCII over high speed Morse code would make any sense? Haven’t done it yet?

    Might make an interesting way to check e-mail while on the road?

    John

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