[OZAPRS] (no subject)

[Glen English VK1XX]

howdy

yeah I did alot with the radio broadcast standard DRM years ago.. got to
know it and HF data comms pretty well. Still maintain my ASAPS license,
etc amongst others,  but I no longer run my own ionosondesince moving to
canberra (suburbia constraints)

the broadcasting  mode of course, the receivers cannot ask for repeats :-)

You are right,  single carrier high QAM modems work well ....unless the
path is changing rapidly, like sunrise sunset vertical incidence. 
(which even the DRM mode D doesn't quite keep up with) , that's pretty
much the thin edge of the edge in HF broadcasting as you probably know....

pays to stay at the MUF to keep the multihop to a minimum, of
course...although that's living dangerously on reliability/ realtime
measurement of path MUF required, did some of that.. interesting stuff.

It's an interesting area. I'll make sure I make time to have lunch with
you next time I am in town.


On 18/10/2017 2:33 PM, Matthew Cook wrote:
> Hi Glen ,
>
> I've been fortunate to have played with these systems and for what is
> old tech (FEC, block encoding & Turbo modems) they still work well. 
>  I've seen STANAG 4539 modems hanging onto 600 bps connections at -2dB
> SNR dropping back to 75 baud at -18dB SNR.  Some times it is not about
> the speed over the forward path.   Doing 64QAM in 2.7kHz of BW is
> still impressive with good channel SNR.
>
> Anyway one day we'll get some of the more funky modem topologies to
> play with. David DGR has been doing some good work with n-ary PSK
> modems of late, which has been interesting.
>
> 73
>
> /M.
>
>
>
> On 18 October 2017 at 07:50, Glen English VK1XX
> <glenlist at pacificmedia.com.au <mailto:glenlist at pacificmedia.com.au>>
> wrote:
>
>     thanks for the link Matthew. yeah most of those HF modems are a POS
>     compared to modern OFDM based modems at any sort of decent data rate
>     (although they are alot less demanding on th transmitter due to being
>     constant envelope ) . IIRC the STANAG modem heavily used
>     compression to
>     achieve the reasonable speeds (of plain text transfer)- I think it
>     slows
>     down alot for black comms as it doesn't readily compress as well.
>
>
>     g
>
>
>     On 17/10/2017 5:26 PM, Matthew Cook wrote:
>     > STANAG 4539
>
>
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