[GreenKeys] ITTY stream... language?

[Ralph Irish]

At the deepest level, or at the 'mechanical level', the 'code' in use is a BINARY
code in that Mark & Space equal a logic "1" or a logic "Ø" to accomodate the 
Teletype code, often mistakenly referred to as the "Baudot Code".  For transmission
purposes, there are two frequencies generated.  

If some form of audio is fed into the "MIKE INPUT" or "AUDIO LINE IN" to a SSB
transmitter, the end result is a shift of a certain number of hertz to create the
'code'.

If it is done at an RF level, then the frequency shifts (let's say) 170 hertz at the
RF level and on the receiving end, the receiver puts out two audio tones representing
MARK and SPACE which is fed into some kind of Terminal Unit which then feeds some
kind of teleprinter, often an actual Teletype machine.

DON'T get hung up on MARK = logic Ø and SPACE = logic 1.  Sadly, even after several
decades of teleprinter traffic on the various radio bands, this is not a firm
definition.  Most Terminal Units have a 'Reversing Switch' which can put the entire
system into a mode where something useful and recognizable shows on paper.

One nice advantage of this is if there is interference on the "NORMAL" setting of
one's TU, it is possible to shift one's receiver to the other sideband and move the
Reversing Switch to the opposite position.  If this still does not work, then one
must do what is possible to adjust Bandpass controls and 'Centering' controls to
eliminate as much of the interference as possible.

Some TUs were designed to run reasonably efficient when only decoding the MARK or
SPACE frequency.  DOVETRON units have a selector which does this.  

Three of the five positions of this switch are marked:

"MO" for Mark Only decoding; "MS"  for Mark & Space decoding and "SO" for Space Only
decoding.  I have used this feature to great advantage over the years.

Some other TUs will operate reasonably well if one can 'filter out' the  SPACE tone,
in the Receiver to feed only the MARK tone from the receiver to the Terminal Unit, 
and conversely, possibly filtering out the MARK tone in the Receiver to feed only
the SPACE tone from the receiver to the Terminal unit.  Some TUs may have a control
which might be slightly adjusted in these circumstances to compensate for the
missing audio tone.  Please don't pin me down on specific TUs or the names of the
controls.

This is a situation where "Trial and Error" comes into play, much of the time.  If
you find a working situation for doing any of this,  WRITE IT DOWN AND KEEP THE NOTE
WHERE YOU CAN FIND IT IN A HURRY!

I suspect that some G/K people might not totally agree with my observations above,
but having used some simple receivers and very basic TUs over the years, all I can
say is that 'diddling and fiddling' is sometimes your best friend!

For many of the G/K people, who are getting their 'signals' from the internet,
interference problems usually don't exist.  One is simply getting an audio signal
from an 'Audio Out' point on a computer and feeding the audio into a TU.  

-   -   -   -

I hope I've not gone too far astray as to cause confusion, as opposed to some clarity.

For now,

73,

Ralph - W8ROI

(I realize that this might be a situation of someone asking the time, 
 and me giving instructions on how to build a clock.  I tend to do that.)


-   -   -   -   -   -   -   -


On Jan 2, 2020, at 4:17 PM, John, W9DDD wrote:

> I've been down this trail, it's mp3.  Browser says audio/mpeg, Render mode: Quirks mode.  Not a lot of help, sorry.
> 
> Seems like I had some other information, if I find it, I'll send.  It's been a busy last two months and I haven't looked at it for a while..
> 
> Let me know if you have any luck with python.
> 
> John, W9DDD
> 
> On 1/2/2020 3:07 PM, E. wrote:
>> Hey - for those who knows about the ITTY stream…
>> …what language does the audio stream output?  Is it binary, etc.?  Trying to figure out how to do a Python Script with it.
>> Thanks much and Happy New Years all!
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