[GreenKeys] ITTY stream... language?

[Steve Garrison]

Spot on, Ralph!

Steve G./N4TTY
Sent from my iPhone

> On Jan 2, 2020, at 7:33 PM, Ralph Irish <w8roi at wowway.com> wrote:
> 
> 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.)
> 
> 
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