[GreenKeys] Mystery RTTY Project

[Harold Hallikainen]

Could also do it with a PIC10F200
(https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/DataSheets/40001239F.pdf
) for 60 or 70 cents. Add a power supply and an SSR to key the loop.

Harold
https://w6iwi.org

On Sat, July 8, 2023 4:19 pm, Alf Fisher wrote:
> 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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>
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