[RTTY] If you care about CW and RTTY - time is of the essence

[Matthew Pitts]

Well, making the assumption that HF messaging (aka email) is the only draw to ham radio for some people is an example of rock bound thinking, as is thinking that the only kind of busy channel detection that could be used is the kind that stops a transmission if there is a signal in the passband.

Matthew Pitts
N8OHU 

On August 17, 2016 1:01:19 PM EDT, Kok Chen <rtty at w7ay.net> wrote:
>
>> On Aug 17, 2016, at 7:20 AM, Al Kozakiewicz <akozak at hourglass.com>
>wrote:
>> 
>> In an all analog world, it makes some sense to regulate transmissions
>based on content. In a digital world, it does not. There is no
>syntactic difference between text, image, an Excel file or any other
>non-streaming data source.  It is all data.
>
>Please allow me to play the pedant for a moment, then follow with less
>off-topic comments below.
>
>What we have on HF *is* an all analog world.  This is why we need
>modems that allow us to take discrete data and convert them to analog
>waveforms which then make use of the “analog” mechanism of data
>transfer.
>
>One exception is perhaps Henning Harmuth’s work on directly
>transmitting “square waves.”  The basis of his “waveforms” are based on
>the Walsh functions instead of sinusoids.  
>
>Harmuth's “spectrum” consists of coefficients of the Hadamard
>transforms, rather than the Fourier transforms that we usually
>associate with a “spectrum.” (In mathematics, a spectrum is a pretty
>general animal.)
>
>Harmuth’s “carrier,” being a Walsh function, would spread from DC to
>infinity in the Fourier space.  By the same token, a sinusoidal carrier
>would spread from DC to infinity in the Hadamard transform space.  The
>two will never coexist peacefully, and Harmuth has said as much.
>
>This part of Harmuth’s work was published in an Academic Press book in
>the series “Advances in Electronics and Electron Physics,” Supplement
>14, “Nonsinusoidal Wavesform Radar and Radio Communications,” ISBN
>0-12-014575-8, and even included chapters on antennas for this type of
>waveforms.
>
>That being said, what we have in the all-modem (a.k.a. digital) world
>has equally bad consequences when you mix narrow and wide band signals.
> 
>
>The extreme example are spread spectrum (Hedy Lamarr’s invention, bless
>her soul) and something like RTTY or CW, and is a reason why spread
>spectrum is still not allowed for amateurs below 29 MHz.  
>
>At least in the case of spread spectrum and CW or RTTY, the damages are
>lowered performance, and not complete incompatibility — spread spectrum
>will appear to a CW or RTTY op as a raised noise floor, and narrow CW
>will appear to a spread spectrum signal as errors that are correctable
>by FEC.
>
>It is actually a less extreme case where the problem is possibly
>greater.  
>
>A wideband digital signal is not spread evenly in the spectrum (they
>won’t dare claim to be spread spectrum for fear of being banned by the
>FCC) to simply appear as a raised noise floor to a narrow band RTTY
>signal.  The wideband signal has spectrum structures that will (not
>“may”) cause harm to RTTY, especially since RTTY has no error
>correction.  Take it from someone who has occasionally dabbled in RTTY
>modem techniques, a wide “digital" signal will cause harm to RTTY, and
>vice versa, if the two are allowed to intermingle.
>
>Sure we can add FEC to RTTY, but we are a *hobby*, folks.  We (the
>royal “we," since I haven’t even used keyboard CW in a decade :-) still
>use CW, and that is as inefficient a mode to transfer discrete
>information (OOK) as you can get.   Many aspects of amateur radio is
>not about efficiency (which ARRL lawyers appear to keep harping on) but
>about enjoyment and love of operating.  
>
>Now show me an HF email user who enjoys “operating.”
>
>73
>Chen, W7AY
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