[GreenKeys] ITTY question

Sun Nov 19 22:01:31 EST 2017

Nick,

The old RTTY standard used a 850 Hz shift, with standard M/S tones being 
2125/2975 Hz.

At some point in time, hams moved to a narrower shift of 170 Hz 
(military & commercial stayed with 850 Hz).  For 170 Hz shift, the mark 
tone was kept at 2125 and the space tone moved down to 2295 Hz. So on 
your board, NARROW is for 170 Hz, and CENTER is set for 2210Hz for ITTY US.

For ITTY Europe, with 1275/1445 Hz tones, the center must be moved down 
to 1360 Hz.

I found some info on Erick's board. It uses a standard phase-lock loop 
FSK detector chip, the 2211. I designed FSK  detectors with the 2211 
chip 20-25 years ago, but don't remember the details of it and can't 
tell from Eric's circuit how much range the CENTER control has. But you 
could try adjusting it and see if it will go down that low. Otherwise, 
you will need to make some component changes to copy ITTY Europe with it.

As I remember, you can put a scope on pin 11 of the 2211 (which is the 
same point as the non-grounded lend of the "shift" resistors) and see 
the free-running frequency of the 2211. The CENTER control is adjusted 
to center this oscillator to your FSK signal.

Good luck!

Duncan

On 19-Nov-17 20:32, Nick wrote:
> Thanks Duncan
>
> The only two things I can change on Eric's board is a bridge, WIDE to 
> NARROW - it is bridged to NARROW at the moment and an adjustment 
> screw, named and marked on the board as CENTER.
>
> Nick  -  N0NCQ
>
>
>
>
> Sent from my T-Mobile 4G LTE Device
>
>
> -------- Original message --------
> From: Duncan Brown <duncanancy at earthlink.net>
> Date: 11/19/17 8:18 PM (GMT-05:00)
> To: greenkeys at mailman.qth.net
> Subject: Re: [GreenKeys] ITTY question
>
> Nick,
>
> ITTY Europe uses different tones than ITTY US - you should be able to
> hear the difference.  Your AFSK converter/demodulator must be set up for
> the proper tones. US tones are 2125/2295 Hz. Europe tones are 1275/1445
> Hz. Go to RTTY.com and see
>
>
>     Our RTTY over Internet Services
>
> for details.
>
> I'm not familiar with Eric's board. Does it have capability of switching
> tones?
>
> have fun,
>
> Duncan
> K2OEQ
>
>
> On 19-Nov-17 19:32, Nick wrote:
> > Hi gang,
> >
> > As I posted last week, I aquired a Siemens T37h in a beautiful wooden
> > case (oak) and like to use that machine in the near future with
> > iTelex. I got the machine running and the dialing until is repaired.
> > Our iTelex-guru, Henning from Germany want me to do a final test
> > before we go iTelex. He want me to copy ITTY EUROPE (50 baud, I guess)
> > to see if absolute everything is in order with the T37 and the dialing
> > until.
> > Using Eric's demodulator board, I can copy ITTY news America on my
> > 28KSR without a problem. Trying to copy ITTY EUROPE on the T37, the
> > demodulator board doesn't do a thing, but I can hear the tone coming
> > out of my PC and/or phone. It is not about what machine I am using,
> > it's about that the demodulator is not kicking in. I know, on the
> > demo-board is an adjustment screw for fine-tuning but I still can't
> > get the board into action.
> >
> > Anybody with any info on my little challenge ???
> >
> > Nick  -  N0NCQ
> >
> >
> >
> > Sent from my T-Mobile 4G LTE Device
> >
> >
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