[time-nuts] RS 232

[Bob Camp]

Hi

There's also the time honored approach of generating the side tone off of the generated RF. In that case the latency to the transmitter would matter quite a bit. I have no idea *why* you would run the key through a computer in that case ….

Bob

On Jul 26, 2013, at 4:52 PM, Jim Lux <jimlux at earthlink.net> wrote:

> On 7/26/13 12:50 PM, Didier Juges wrote:
>> There is a difference between managing the latency (as in ensuring that sound and video are synchronized, but latency itself is acceptable) and minimizing the latency as in a Morse code keyer where the operator has to manually control the generation of elements that can be as narrow as 20mS (one dit at 60 words per minute) while getting timely aural feedback. That means you need the sound to start and stop within less than about 5 mS following the key closing and opening.
>> 
>> It is trivial to do on a microcontroller running at 1MHz but surprisingly harder to do on a 2GHz Windows machine.
>> 
>> It is not just a matter of time stamping the key closure, you have to get the sound system starting and stopping.
>> 
> 
> Yep. although, since the propagation path is on the order of 100 milliseconds, providing feedback to the user directly from the interface works quite well (e.g. generating tones directly from the keying).
> 
> The challenge is trying generate the sidetone through Windows.   But really, there's no reason why you can't have a "keying box" that provides the direct side tone and sends the events to the host computer.  Then the issue is more about keeping constant latency (or else the CW will be really, really hard to copy)
> 
> It's not like an extra 10 milliseconds of delay between keying and the emitted RF waveform makes any difference at the other end.
> 
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.