[GreenKeys] Halloween Broadcast 2020 length

[Paul Heller]

OK, I’d love to turn down the bit rate for ITTY. I originally had it lower and some folks were reporting troubles so I bumped it back up during debugging and never put it back.  I’ll bump it down for ITTY and you folks can report any issues to me.

As to what generates the tones, it is real hardware. ITTY uses the ST-8000a, which generates a perfect tone and is very reliable.  The audio gets fed into a raspberry PI running darkice and icecast. You can see the setup here:

https://www.youtube.com/watch?v=Hpek2ujfGQ4

The video is a bit old but close enough to how it looks today. There is new hardware in the rack and there are also four channels now. But the basic design has not changed in years. Here is the rack today:




I have it set up so if the power goes down it will automatically come up operational when power is restored. It has been a real labor of love, but the past year or so it has needed little maintenance. 

It works well because of Tom Tillson. He’s the caretaker. I run the infrastructure, he runs the service.

Paul
W2TTY
i-Telex: 80003

ITTY:  		HTTP://INTERNET-TTY.NET:8000/ITTY
ITTY100:  	HTTP://INTERNET-TTY.NET:8010/ITTY100
AUTOSTART:  HTTP://INTERNET-TTY.NET:8030/AUTOSTART
EUROPE: 	HTTP://INTERNET-TTY.NET:8040/EUROPE


> On Nov 5, 2020, at 4:03 PM, Harold Hallikainen <harold at w6iwi.org> wrote:
> 
> I'm having fun watching autostart ITTY!
> 
> What is actually generating the tones? I assume it's software. Is there a
> low pass filter before the modulator? Also, I suspect the telephone
> standard of 8,000 samples per second with 8 bits per sample would be more
> than adequate. When I start work on my DSP-based ideas, I plan to use 8
> bit, 8,000 samples per second. I'll convert the incoming audio to and do
> the math as double precision floating point.
> 
> Thanks!
> 
> Harold
> 
> 
>> For what it’s worth, here is what I do to the ITTY audio before sending
>> it out:
>> 
>> Sample Rate = 11025 Hz
>> 16 bits per sample
>> MONO (no need for stereo)
>> 
>> And I put on a low pass and high pass filter at 3000 and 1500
>> respectively.
>> 
>> These settings really helped to optimize the stream
>> 
>> Paul
>> W2TTY
>> i-Telex: 80003
> 
> 
> -- 
> FCC Rules Updated Daily at http://www.hallikainen.com
> Not sent from an iPhone.

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