Date: Tue, 9 May 2000 21:22:36 +0200
Message-ID: <4.1.20000509200851.01da91b0@mailer.inrete.it>
Data: Tue, 09 May 2000 20:21:44 +0100
To: rsgb_lf_group@blacksheep.org
From: "M. Bruno" <spin@inrete.it>
Subject: Re: LF: DFCW  Parameters
In-reply-to: <E12pDrN-0002RU-00@mserv1a.u-net.net>
Riferimenti: <3.0.1.16.20000509164652.223f2124@mail.cc.kuleuven.ac.be>
MIME-Version: 1.0
Content-Type: multipart/mixed;
 boundary="------------080804040108080109000002"
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Sender: <majordom@post.thorcom.com>

This is a multi-part message in MIME format.
--------------080804040108080109000002
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 8bit


>ON7YD wrote:
>> DFCW is still a very experimental mode, so not very standardized yet.
>> Generaly accepted is that the higher frequency stands for 'dash' and the
>> lower for 'dot'. The frequency shift is dependent on the dot length. For 3
>> seconds per dot (that has become a kind of informal standard) a shift of
>> 4Hz is used. A 1 second 'gap' is used to separate the elements (dots and
>> dashes) within a character, characters are separated by a gap of 1 dot
>> length, words by a gap of 2 dot lengths.
>
>Rik,
>
>Have I misunderstood, or are you saying there is a gap between 
>each dot and each dash? I thought there was no need to do this as 
>the frequency determines whether an element is a dot or dash so a 
>dot three times the dot lenght must be three consecutive dots.
>Probably me being dumb.
>
>
>Mike, G3XDV (IO91VT)
>http://www.dennison.demon.co.uk/activity.htm
>

Mike, a gap (even small) helps a lot to recognize a character.

After a discussion with Alberto I2PHD, we suggest a modified version
of DFCW, with, probably, an even higher resistance to QRM.
Let transmit three frequencies, the higher for the dash, the
middle for the dot, the lower (equally spaced) for the "key up".
The advantage is to always have a carrier, and being easier
to detect a space between characters in noise.

The output will be like:

 ___ ___                           ___ ___   ___                          
___     ___
         ___ ___ ___   ___ ___ ___               ___ ___   ___   ___ ___      
___
_   _   _   _   _   ___   _   _   _   _   ___   _   _   ___   ___   _   ___  
_   _   _

(use fixed spacing characters to see)

I try to attach a small ASCII file to this message; have a look, there is also
an example with the "space" frequency between dot and dash.

To modify the TX is very easy, at least for me; I will do some tests in this
way by next weekend. No modifications to existing QRS program are necessary,
only a manual RX/TX switch.

About the frequency difference, there are of course no fixed rules, but don't
be too wide. It's easier to see closely spaced signals, like 10 times the
resolution used by the receiving program. 1-2-4 Hz and/or multiples and
submultiples seems practical.

73, Marco IK1ODO


--------------080804040108080109000002
Content-Type: text/plain; charset=windows-1252;
 name="dfcw2.txt"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
 filename="dfcw2.txt"

 ___ ___                           ___ ___   ___                           ___     ___
         ___ ___ ___   ___ ___ ___               ___ ___   ___   ___ ___       ___
_   _   _   _   _   ___   _   _   _   _   ___   _   _   ___   ___   _   ___   _   _   _


___ ___                            ___ ___   ___                           ___     ___
_   _   _   _   _   ___   _   _   _   _   ___   _   _   ___   ___   _   ___   _   _   _
         ___ ___ ___   ___ ___ ___               ___ ___   ___   ___ ___       ___

--------------080804040108080109000002
Content-Type: text/plain; charset=windows-1252;
 name="ATT06490.txt"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
 filename="ATT06490.txt"

Marco Bruno - IK1ODO
spin@inrete.it

SPIN Electronics - www.spin-it.com

--------------080804040108080109000002--