[Lf] [Fwd: LF: RE: TransAtlantic II]

[Andre' Kesteloot]

Talbot Andrew wrote:

> It would be unfortunate to limit ourselves to just use of these two
> relatively simple pieces of DSP software which at the end of the day are
> really just narrowband power detectors in not that narrow a bandwidth.
> Remember, the very first long distance QSO on 73kHz between myself and
> G3PLX was made in 0.04 Hz bandwidth using something like 300uW ERP with
> plenty of signal in hand - whereas the likes of Spectrogram can only get
> down to around 1.3 Hz BW.  The same bandwidth can be achieved with a
> filter made from 5 watch crystals at 32 kHz - I've done it.   .
>
> I feel there is a lot more to be gained by coherent integration
> techniques.   Use of the VE2IQ software and other slow BPSK modes goes
> some way towards this, but all suffer badly from the need for clock
> recovery and tracking.  The need to get initial timing information
> throws away much of the usefulness of this mode.
> The ultimate solution is to use GPS timing.  I know quite a number of
> operators in the US are now using GPS locked frequency and time sources,
> and they are begining to make an appearance here.   Having the
> transition points of the bit intervals known precisely to the
> microsecond (if the path length is known) leaves the signal recovery
> task to be merely an integration over whatever time is needed for the
> bandwidth with no lockup or preamble phase.
>
> TAPR have a range of GPS and frequency locking projects / kits.   Who in
> the US Lowfer community have the DSP hardware, even if not the
> programming skills, to experiment with these techniques.  Ideally, if a
> Motorola DSP 56002EVM module, GPS receiver and carrier frequency known
> accurately to milli Hz are availble software can be shared and
> experiments made with known equipment capabilities.
>
> Some people are going to spend lots of time/money/effort on antennas and
> PAs, why not put a similar effort into signal processing as well.  So
> what if it takes 10 hours to send a message, at least it will have been
> sent from a station that does not have a farm on which to erect huge
> antennas.
>
> Andy  G4JNT
>
> >From VA3LK
>
> >There is precious little time left to develop computer DSP skills, such
> as
> >expert use of the software Spectrogram and Gram, .........- we have
> begun to understand the issues >involved in bringing TransAtlantic II to
> an operational status.
>
> --
> The Information contained in this E-Mail and any subsequent correspondence
> is private and is intended solely for the intended recipient(s).
> For those other than the recipient any disclosure, copying, distribution,
> or any action taken or omitted to be taken in reliance on such information is
> prohibited and may be unlawful.