I wrote a Morse decode for demonstration for a friend for a ham
convention in the early 70's on a PDP8/e. It was designed to be
speed tracking and worked quite well on hand sent code. The
algorithm I used was to base the starting speed on the the last
received character and analyse the speed of the received
character to update the received speed. I remember two
things debugging the code. For a while small noise pulses
were interpreted as dots and were hard (at the time) to filter
out in software. the second thing that should not have been
a surprise was the dit / dah ratio in hand sent code was far
from close and we did some tracking on the ratio as well.

It was a weekend project I wrote the code and Roger Grant
created a interface to a receiver. It was a hit around the ham
convention. One of the attendees was an old railway telegraph
operator whose code on a straight key might as well have been
machine generated. The console on this old computer was
a teletype and his code might as well have been typed from
a file.

The code is somewhere in the historical records department
at Byte Craft then all I need is to find a paper reader that
has been run in the last 20 years.

w..


David VanHorn wrote:

> > The sounder already works but the code is un-clean. I'm still well under 200
> > words. I think that I can fit a complete sender and receiver in the smallest
> > available pics (12{c,f}508} with an external eeprom for some fun projects.
>
> I'm interested to see how you implement the decoder part, particularly
> with off-air signals.  I know the boxcar integrator approach for tone
> filtering, I've used it in several DF projects, but hadn't thought
> that you could implement it in a more wideband version.
> --
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist


-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist