[Fwd: LF: Re: visual-CW]

Andre' Kesteloot akestelo@bellatlantic.net
Fri, 12 Nov 1999 20:51:32 -0500

Steve Olney wrote:

> G'day Rik,
> I can indeed confirm that this slow visual CW works.  It was one of my
> early attempts to figure out a way of improving the S/N on LF paths.  It
> had one tone for the "dots" and one for the "dashes" spaced by 10Hz each
> lasting for 30 seconds which were fed to an SSB transmitter.  The only
> difference I had was that I sent a middle tone for the spaces between
> characters and words.  I found that it was easier to determine the presence
> of a carrier rather than an absence for a space and to actually separate
> each "dot" or "dash" with a space tone.  This method is slower than the
> method you suggest by a factor of about two. This middle space (or idle)
> frequency also is an aid for tuning and gives a base line for the "dots"
> and "dashes".   I had 1000Hz for the space (or idle) 1005Hz for the "dash"
> and 995Hz for the "dot".   What are your comments on this?
> The software didn't have a morse code generator, just random "dots",
> "dashes" and spaces between them to test the method.   However, I got bound
> up with my FDK method and in the process of developing the code for FDK, I
> cut this slow FSK code out and I will have to rework it in the future to
> get it back.
> BTW, while tests have shown that FDK is better than PSK31 by about 17dB and
> better than about 10dB better than a reasonable speed QRSS,  I feel that
> the slowness of data transmission (one character/minute) and the stability
> required (about 0.02Hz over one minute) will mean that FDK will not be
> practical or attractive for nobody but the most dedicated.  In other words,
> not enough gain for the pain.  It also requires synchronisation of the PCs
> at both ends to within +/-10 seconds and has a fixed data rate of one
> character/minute.
> So all in all,  I will still play with FDK and prove it works over long
> paths, but I will probably drift back to the slow FSK CW method and develop
> it more.   The good thing is that everybody can use it and the speed can be
> adjusted to suit the conditions as you have indicated, unlike FDK.
> You obviously have progressed further than anyone else along this path and
> as a user of your excellent QRSS program I (as well as others) was
> wondering if you have developed your software to a point where you can let
> others have a go?   I haven't worked out how to drive the soundblaster
> directly from data in memory (I'm not clever enough to do that yet) so the
> quickest my software could output the tones is practically every 15 seconds
> or so.  You obviously have solved that problem or do you actually shift the
> frequency of the carrier?
> Anyway, this post is already too long, but I'm sure there are many of us
> eager to try out your program and this great idea.
> 73s Steve Olney (VK2ZTO/AXSO - QF56IK : Lat -33 34 07, Long +150 44 40)
> =============================================
> LowFer URL:
> http://www.zeta.org.au/~ollaneg/lowfer.htm
> AXSO LF Experimental Station URL:
> http://www.zeta.org.au/~ollaneg/axsoextx.htm
> LF Receiving - FRG-100, CHA antenna
> LF Transmitting - 177.5/177.4kHz 8W - 7.6m vertical or CHA
> Modes - AM, SSB, PSK31, SSTV, Hellschreiber, QRSS
> and a new experimental mode - FDK.  See this URL for more:
> http://www.zeta.org.au/~ollaneg/FDK.htm
> =============================================