[GreenKeys] Mystery RTTY Project

[Alf Fisher]

Harold,
I cant see how a square wave would work.
If you listen to an off-air RY signal it has rhythmical brrr, brrr, brrr 
but a square wave wouldn't have the rhythmical breaks that make the stop 
bits.

There was an article for an RY generator by W7ZTC in the March 71 issue 
of Ham Radio.
It used some really old RTL chips MC-890-P and MC-824-P.
Maybe someone could redesign the circuit using standard LS TTL or CD4000 
series chips.

Alf G3WSD



On 08/07/2023 23:49, Harold Hallikainen via GreenKeys wrote:
> That IS pretty clever! I assume the printer has auto CRLF since the
> generator would only generate RY. Also, all bits would be the same length,
> including the stop bit which, for 60 wpm is usually 31 ms long compared to
> 22 ms for the other bits. But, if we are sampling in the middle of the
> bit, it seems like any stop bit longer than 11 ms would work. Thinking
> about the square wave, I get
>
> 0 - start
> 1 - D0
> 0 - D1
> 1 - D2
> 0 - D3
> 1 - D4
> 0 - stop
>
> So, it seems like we'd get framing errors on a square wave since the stop
> bit is a 0.
>
> Harold
> https://w6iwi.org
>
> On Sat, July 8, 2023 3:41 pm, Skip Macaulay wrote:
>> Wild project, real bread " board" stuff !!
>> Skip
>>
>> Skip MacAulay
>> VE6BGT
>>
>> On Sat, Jul 8, 2023, 4:20 PM B. Smith, <smithab11 at comcast.net> wrote:
>>
>>> Several have figured out the project. The RY's are generated by sending
>>> a square wave using a 555. The 555 then drives an HSR series optical
>>> switch which keys the local loop. Dovetron does a similar operation with
>>> their RY generator. There are plenty of Chink 555 boards on ePay that
>>> are all ready built and cost is around 2 bucks.
>>> Photo Attached.
>>> K4CHE
>>> http://k4che.com/Tempvideo/RTTY%20Mystery%20Project/Mystery%20K4CHE.mp4
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>