Topband: DSP and Latency

[Richard (Rick) Karlquist]

There is a very straightforward fix for this latency.
Simply use a POTS telephone line with a phone patch.
Receive audio comes in, and CW tones go out.  At
the remote site, a tone decoder generates key closures.
I measured 50 ms latency on a 100 mile phone connection.
And you never get audio glitches.

Rick N6RK

On 3/18/2015 7:38 AM, Bill Cromwell wrote:
> Hi Jim,
>
> I have begun playing with soundcard SDR and DSP software. "Latency"
> varies all over the place (from config to config) and can be somewhat
> managed. The real sticking place for me is the delay between pressing
> the key (CW of course) and the beginning of the dit or dah. Again when
> releasing the key and the end of the dit or dah. When the radio is right
> in front of me, I can use an external 'sidetone' and coordinate my
> keying hand with that. I am not sure how that is handled with a remote
> station setup. Perhaps the remote user is using a local sidetone or even
> sending with a keyboard. If it's computer generated CW from the keyboard
> any 'latency' just won't matter. It's milliseconds or less - not minutes
> or hours.
>
> Maybe this comment will help some others get a better handle on this
> 'latency'.
>
> 73,
>
> Bill  KU8H
>
>
> On 03/18/2015 07:27 AM, Jim Brown wrote:
>> On Wed,3/18/2015 12:14 AM, Mark van Wijk, PA5MW wrote:
>>> Audio latency 'differences' can be shown in the shack already;
>>
>> Yes. I mentioned that A/D and D/A conversions take time. So do DSP
>> processes. The word that describes this time is latency. It is not
>> limited to audio.
>>
>> I had to learn about all of this more than 20 years ago, because I
>> worked in pro audio, when we began to use DSP extensively in large
>> sound systems.
>>
>> 73, Jim K9YC
>
> _________________
> Topband Reflector Archives - http://www.contesting.com/_topband
>
>