Re: HF DV:


Stuart Longland VK4MSL
 

On 18/03/17 11:20, Eubank, Greg (MVA) wrote:
My initial thoughts are, that if there was a DV implementation that
utilized Pactor Error detection and correction technology, that an HF DV
protocol could theoretically be designed to provide similar performance
of the Pactor method for Modulation/Demodulation.
https://en.wikipedia.org/wiki/PACTOR seems to suggest you'll have to
sweet-talk SCS into making a software version of their (proprietary)
modem to run on Linux/armhf.

I wish you luck.

It is worth noting that DV is a very different beast to data. Audio
delivery is hard real-time. If each character of this email was
delivered with a random 1-3 second delay… it would be annoying to watch
but not harmful to the intelligibility of the message.

However, if a burst of no --- i --- se --- ca --- used delays playing
back parts of an audio recording… this discontinuity of playback is
disastrous. The broken-up signal cannot be understood, even though no
audio samples have been lost, the human brain cannot process the parts
in this disassembled manner.

Data modems are intended on getting a packet of data from A to B
*perfectly*. A single bit error means the data at the other end is
corrupt and therefore useless. So they achieve lower BER by long
synchronisation runs and lots of FEC.

Voice modems are intended for constant data rate, and will generally
produce a higher BER, but can synchronise very quickly, thus will handle
sudden loss and return of signal better.
--
Stuart Longland (aka Redhatter, VK4MSL)

I haven't lost my mind...
...it's backed up on a tape somewhere.

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