Again, why couple a better code to higher speed with poorer S/N
and wider bandwidth? Why not stick with 45.45 baud and compatibility
with all the MMTTY/Windows installations linked to EXTFSK with its
fixed 45.45 baud rate (as well as compatibility with the 45.45 baud
specific RTTY filters in several transceivers)?
73,
... Joe, W4TV
On 6/27/2012 8:33 PM, Robert Chudek - K0RC wrote:
> The *BARTG High Speed Sprint* might be an existing (recently introduced)
> contest to make the transition?
>
> 73 de Bob - KØRC in MN
>
> ------------------------------------------------------------------------
> On 6/27/2012 3:43 PM, Paul Stoetzer wrote:
>> Somebody should set up an ASCII contest. That would be interesting.
>>
>> Paul, N8HM
>>
>> On Wed, Jun 27, 2012 at 4:36 PM, Kok Chen <chen@mac.com> wrote:
>>> On Jun 27, 2012, at 12:47 PM, Alex Malyava wrote:
>>>
>>>> Why don't we just invent/introduce some new RTTY standard -
>>>> the one with 6 bits instead of 5 - covering whole alphabet and digits
>>>> without any FIGS/LTRS and speed it up a little bit to compensate an extra
>>>> bit?
>>> There is no need to introduce another "mode du jour" even.
>>>
>>> 7-bit ASCII (CCITT ITA-5) RTTY has been FCC approved (see part 97.309(c))
>>> for a long time now. fldigi supports it, so does MultiPSK and cocoaModem,
>>> among others.
>>>
>>> In a discussion (a year or even longer ago) on this reflector, I had shown
>>> that for most RTTY contest exchanges, ASCII RTTY beats out Baudot RTTY in
>>> speed, even when both are running 45.45 baud.
>>>
>>> You get rid of the FIGS/LTRS confusion (thus problem with USOS
>>> incompatibility either; USOS is a Baudot problem), allows lower case, and
>>> it still beats out Baudot in contesting speed. It is when sending
>>> paragraphs of upper case text that Baudot wins over ASCII.
>>>
>>> Because of the Teletype Models 33/35, the popular speeds for running ASCII
>>> RTTY was 110 baud. At that speed, it will wipe the floor with Baudot RTTY.
>>>
>>>> Or drop one stop bit to save the length? Or use 3 frequency FSK -
>>>> shift left is "0", shift right is "1" and middle is sync/start/stop ?
>>> 3FSK may not be a good idea. The reason is that the equalizer to
>>> compensate for selective fading will be at best very complex to build.
>>>
>>> 2FSK has the very unique ability to fight selective fading with a very
>>> simple thresholding scheme. Once you add more tones, you can no longer
>>> build simple ATC circuits.
>>>
>>> For that reason, you will find that there is nothing in MFSK16 (16 tones),
>>> DominoEX (18 tones) or Olivia that explicitly fixes the selective fade
>>> problem -- they all use long interleaved codes to fight QSB in general --
>>> and you may not want to use long interleavers with short contest exchanges;
>>> the latency will need to be over 1 second to be effective. You will need
>>> to add latency to the exchange time. Selective fading happens quite often.
>>> You can almost not avoid it with a Rayleigh path.
>>>
>>> Anyhow, the solution is already at your fingertips, and the FCC has blessed
>>> it for years now. It is called ASCII. And 110 baud with 170 Hz shift is a
>>> breeze.
>>>
>>> 73
>>> Chen, W7AY
>>>
>>>
>>>
>>>
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