[hpsdr] Latency

[CT1IZU]

Below is an interesting and relevant cut of a recent message on the Star2 
reflector. Star2 runs a DSP IF at 15Khz on either the old EzLite, H/B AD2181 
or Lyle´s dspX.


 (((((((This note prompted by a review in March Radcom of a couple of SDR 
boxes -page 51 And some enquiries on general PC-based SDR behaviour on this 
critical figure of merit.

LATENCY - the time from an event on the input (of an Rx or Tx) until it 
appears at the output. With these PC/SDR boxes we are talking three or four 
HUNDRED milliseconds for Rx and same again for Tx. This is comparable with 
time for sending HI at 25wpm. I had no idea we were talking these big 
numbers.

You can imagine the impact on trying to work Dx if the soonest your signal 
could ever get to the Dx after his last key-up was 1 second. And you can
imagine what a whole second of ambiguity-time would do to doubling in a VOX 
conversational net.

FYI, STAR latency is approx 12 ms - . But we don't have the burden of an 
operating system! At least not one that
Bill G would recognise as such. A major benefit of running software that is 
only there to support an HF radio. Nothing else.)))))))))))))))

Shel CT1IZU