[Lf] PSK-08 ?

[Andre' Kesteloot]

Talbot Andrew wrote:

> Hello all.
>
> After an absence of well over a year I'm now back on LF with a rebuilt
> transmitter (similar to G0MRF type) and 250 Watts reliably.  Antenna
> tested out - still OK ! - but as its only a 7m high Tee is probably a
> bit small by modern standards on the bands.  ERP estimated at -22dBW
> based on an antenna current of 1.5 Amps and effective height roughly
> equal to it's actual figure.
>
> Now using a transverter driver from an IC746 so linear modes from DSP
> are no problem.
> I'm looking for LF operators who have access to a 56002EVM board in
> order to try PSK08.   This is my adaptation of PSK31 for use on LF but
> running 4 times slower.  The operating signal bandwidth is in the region
> of 5 Hz and the data rate supports slow typing speeds - still
> considerably faster than Aural CW
>
> I also have an embyronic version of PSK01but this is more difficult to
> implement on the EVM due to the need for longer length filters.  At the
> moment it works but has responses every 16 Hz,  rolling off gradually.
> Frequency has to be set to within 0.2 Hz or 0.1 Hz for the QPSK mode.
> Frequency setting is only within 1 Hz at the moment due to the
> oscillator accuracy in the 746, but this is stable and I can separately
> calibrate to sub mHz accuracy for specific tests.
>
> Re. Michael's comment below,   -29dB in what bandwidth ?   Remember the
> 393km QSO I had back in the dark ages of LF with G3PLX on 73kHz.  That
> used a bandwidth of 70mHz and (Very) Slow CW with a 40 second dot
> period.   The S/N for that signal would have been in the region of -26dB
> in the 'normal' CW bandwidth of 300 Hz, and there were a few dB in hand.
> Also bear in mind that Spectrogram type reception relies on incoherent
> visual assessment of colour scales.  Proper coherent signal integration
> can give probably 3 - 6 dB improvement on this - hence my interest in
> being able to run tests with PSK08 and PSK01.
>
> Noise levels on the band seem higher than they used to be a couple of
> years ago.  Is this my imagination or have they really increased ?
>
> Andy  G4JNT
>
> > Who has experience with <-29dB to noise level signal identification?
> > CoherentCW, PSK, SlowCW, dedicated DSP algotithms? There are lock-in
> > amplifiers using similar techniques maybe we can benifit there.
> >
> > Best 73's and gl on lf
> > Michael Sanders, PA3BSH
> >
> >
>
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