Bill,
RTTY isn't a digital mode? Why are you dragging the start and stop bits
into it? The fact that digital information is sent asynchronously has
nothing to do with it. The 5 bit code patterns sent over a RTTY modem
represent numbers. Note part 97's reference to "digital codes" below:
Part 97 : Sec. 97.309 RTTY and data emission codes
------------------------------
(a) Where authorized by Secs.
97.305(c)<http://www.w5yi.org/page.php?id=137>and97.307(f)<http://www.w5yi.org/page.php?id=139>of
the part, an amateur station may transmit a RTTY or data emission
using
the following specified digital codes:
(1) The 5-unit, start-stop, International Telegraph Alphabet No. 2, code
defined in International Telegraph and Telephone Consultative Committee
Recommendation F.1, Division C (commonly known as Baudot).
--------------------
So it appears that the FCC thinks that RTTY is a digital mode. When sent
over the air via FSK it has a digital mode emission designator of F1B
(Frequency modulation, digital, machine reception). Note the word "digital"
there. The ARRL thinks RTTY is a digital mode too. I know they don't carry
the weight of the FCC, but it just shows that you've got a lot of people out
there to straighten out :-)
73,
Doug, K4DSP
On 10/14/06, Bill Turner <dezrat@copper.net> wrote:
>
> ORIGINAL MESSAGE:
>
> On Fri, 13 Oct 2006 20:03:35 -0400, Bill Coleman <aa4lr@arrl.net>
> wrote:
>
> >RTTY is digital.
>
> ------------ REPLY FOLLOWS ------------
>
> No, RTTY is a binary (two state) mode, but it is not digital, any more
> than CW is. People have fallen into the trap of thinking that because
> a signal has two states, it is digital, but such is not necessarily
> the case. For a signal to be digital, the bits have to represent
> numbers and in the case of both RTTY and CW, that is not true.
>
> In a digital system the length of a bit is of no consequence, but in
> both RTTY and CW, it is. RTTY uses a stop bit that is longer than the
> others and that is how the decoder knows it is in fact a stop bit.
> With CW, the difference between a dot and dash is crucial, where in a
> digital system they would both equal the same number.
>
> Long before digital computers existed, RTTY was being decoded with an
> analog computer known as a teletype machine. No numbers involved.
>
> Bill, W6WRT
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> RTTY@contesting.com
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>
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