[Meteor-Scatter] Perseids and operating procedures!

Thu, 15 Aug 2002 10:15:02 -0400

One important point to consider.  The bandwidth of a properly adjusted
FSK441 signal is much narrower than that of a properly adjusted HSCW signal
of the same speed.  Especially if that signal is produced by MSDSP.  It
would be possible to create a HSCW system that could use zero crossing
points to start and stop dots and dashes, and thus significantly decrease
bandwidth, but there are speed constraints when you do this.  When the speed
gets to the point where there are only 2 or 3 cycles of tone per dot, it is
impossible to use zero crossing points except by constraining speed to those
values that use an integral number of tone cycles per dot.

If one tries to set speed to some value that requires 2.5 cycles per dot,
for instance, the dot would have to be shortened or lengthened by about 20%
in order to use zero crossing.  But a dash being 3 times longer would have
to be adjusted by a much smaller percentage.  This is a simplification, and
it is worse than this in practice.  Thus the dot-dash ratio is affected and
the signal becomes hard to copy by ear.

But even if zero crossings are used, I still believe the HSCW signal will be
wider than FSK441.  It is very hard to provide "soft keying" at the on/off
rates we are talking about.

Of course if you use HSCW at much slower speeds the bandwidth is not as
much, but you will get a lot less letters decoded for a given length ping.
I have often seen a complete callsign and a little more from a 20 MS ping on
FSK441.  At 2000 or 4000 LPM it would not be possible.

My experience is that a HSCW contact at 6000 LPM generally takes about 5
times as long as FSK441 does, when pings are sparse.

73, Russ K2TXB

> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of paul
> Sent: Thursday, August 15, 2002 9:21 AM
> To: Tony Read
> Cc: Goran ANDRIC, S55OO.com; Hannu/OH6MAZ; Meteor Scatter mailing list
> Subject: Re: [Meteor-Scatter] Perseids and operating procedures!
>
>
> In message <[email protected]>,
> Tony Read <[email protected]> writes
>
> Hi Tony
>
> >Heres my 2 cents worth.
> >
> >Get Joe K1JT to write a hscw visual decode program along the
> lines of MSDSP,
> >that allow CW ops to work normally and non CW ops to view the info on the
> >screen.
> >That way we can all go back down the band into the MS section around
> >144.100.
>
> I wonder if anyone would use it in favour of msdsp? I've not been able
> to fault msdsp. I suppose if HSCW mode was bundled in the WSJT suite it
> might make some people try it out of curiosity.
>
> <snip>
>
> >Maybe the HSCW ops (me included) should now start to try running at the
> >higher speed used in the US say 5000-8000lpm make loads of qso
> and spot them
> >on CLX to show that there really is little difference in completed qso on
> >either mode.
>
>
>
> About 12 months ago someone else suggested this and I remember thinking,
> oh no! that's the end of hscw for me (I admit that I need  lots of hscw
> practice) but now, I agree entirely. Most of the short refl that FSK441
> decodes in 40-100ms would result in useful decodes by ear. But that
> raises a question of it's own, do you think that someone who was using a
> package like "wsjt-cw" would be any more likely to observe correct
> operating practice and set up their equipment any better than they would
> for "wsjt-fsk441"?
>
> Anyone looking forward to 43 second periods offset by 11 seconds from
> UTC and occupying +/- 20Khz on 144.100?  :-)
>
> Surely etiquette and ethos are needed not a different software package,
> communicating the principles to newcomers in a positive friendly way is
> perhaps a better solution?
>
> Yup.. up the bandwidth / speed is a good move, but please don't shorten
> the period :-)
>
> >
> >In 6 months of operating WSJT I believe that all the qso I have completed
> >could have been completed on HSCW might just take 10 mins more.
>
> Well I'm willing to give that a go, but you might need to be a little
> patient with me.
>
> Regards
> --
> Paul GW8IZR IO73TI
> http://www.gw8izr.com
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