[GreenKeys] ITTY from Arvada testing

Wed Jul 13 22:54:19 EDT 2016

Good Evening Mr. Heller,

Over the last few days I’ve been putting my M28 kluge back together for the purpose of taking it to the Duke City Hamfest for show-and-tell.  That’s a big maybe on taking it to the Hamfest, but we shall see as the date gets closer.  My reason for taking it to the event is simply to let people watch a teletype in action.  I’m fascinated by the machine and I’m sure a lot of them will be as well.  In case you don’t know, the Duke City Hamfest will be held here in Albuquerque, New Mexico at the Marriott Pyramid Hotel on August 12th through the 14th.

My plan is to use the hotel’s WiFi signal as the source of the streaming audio signal I’ll need to feed my AFSK decoder.  My plan is also to use my Apple iPad Air as the receiver of the WiFi signal and take the analog audio signal from it.  Tonight I set all this up and tested it here at my house just to see if any of it would work.  I think you might be interested in my results.

I am pleased to report that I had flawless copy here in Albuquerque from your signal in Arvada, Colorado.  When I say flawless I mean that I copied several sequential stories and the printer performed perfectly with no typos and no other apparent problems.  I have the analog audio input jack on my test bed wired to loop-through the audio so that I can also connect it to small powered speaker.  I want people to be able to hear what the AFSK signal sounds like.  I was a little surprised that I had to turn the volume control on my speaker up all the way in order to be able to hear the audio signal over the noise of the M28 printing.  I really didn’t think much of it.  I haven’t paid much attention to what the input loading impedance of the “Eric Volpe Current Loop AFSK Demodulator” might be.  It’s enough for me to know that I can get it to work.

To continue with the testing I decided to switch over to the http://www.rtty.com/itty/ <http://www.rtty.com/itty/> feed and listen to the ITTY broadcast.  This feed from Washington State worked just as well as your feed from Arvada, Colorado.  HOWEVER, when I turned up the volume on my audio monitor speaker I was surprised to hear that the ITTY signal sounded much louder.  No changes were made to the iPad other than switching from one URL to the other.

So I decided to measure the difference in the signal levels. For this I used my HP 400FL AC voltmeter.  I simply took the audio loop-through signal that had been going to my monitor amplifier and plugged it into the meter instead.  The signal from Sequin, Washington measured -28 dBm into 600 ohms.  Your signal from Arvada, Colorado measured -39 dBm into 600 ohms.  It’s my opinion that the absolute value of the signal level is not important here.  What is important, or at least interesting, is the level difference between the two signal.  At just over 10 dB, your signal is quite a bit lower in volume than ITTY’s.  Perhaps that’s the cause for some rough copy that people were experiencing.  A demodulator set on the low side for good copy might experience a problem if the signal level dropped 10 dB.  Of course, that’s just my opinion.  I could be wrong.

Thank you for the work you are doing and please let me know if there is anything I can do for you from down here in Albuquerque, New Mexico.

73,

Larry Goga, AE5CZ

> On Jul 4, 2016, at 2:30 PM, Paul Heller <paul0926 at comcast.net> wrote:
> 
> Greetings fellow greenkeyers.
> 
> I am looking for a few people to test the new ITTY feed from Arvada Colorado. This is not a cutover, and there could be problems. But now would be a good time to find those problems. At the moment, the ITTY feed is accessible at:
> 
> http://internet-tty.net:8000/ITTY.m3u
> 
> The real ITTY feed gets its content from some excellent volunteers. I have not yet asked those volunteers to post content to the Arvada based ITTY because the ITTY Mailer is not set up correctly to do so.  That will come in a later round. So for now, ITTY is just feeding some news from a couple of news feeds.
> 
> AUTOSTART is also running in Arvada, but you can't send to it just yet. I will ask for a test for that soon for those who are interested to try it.
> 
> If anyone wants to try it, please do so and let me know the results. And be patient: this is a test so problems can be expected.
> 
> George and I have not set a cutover date yet, so the real ITTY feed still remains in Sequim WA.
> 
> Thanks in advance,
> 
> Paul
> W2TTY
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