[GreenKeys] ITTY from Arvada testing

Fri Jul 15 13:19:55 EDT 2016

THANKS  FOR YOUR HARD  WORK TO KEEP THIS SYSTEM ALIVE!

ED#  

In a message dated 7/15/2016 7:17:19 A.M. US Mountain Standard Time,  
paul0926 at comcast.net writes:

Hi folks,  

I have received some very helpful feedback from  many of you. It is MUCH 
appreciated. I stand grateful for it.

I am going to making some changes, one item at at  time, to see if things 
can be improved.  I don’t want to change several  things at once because then 
we can’t measure it. You will see the Arvada ITTY  feed go offline as I do 
this. I will keep you posted.

The immediate three things I was to try  are:

1. Adjust the signal level. Thanks to AE5CZ
2. Increase the bitrate. It is currently at 16.  Might be too low
3. Make sure my script that grabs the news from  USATODAY and BBC is only 
capturing pure ASCII and not erroneously sending out  FIGURES.

George looked at the signal in MMTTY and saw that it wanders off  
frequency.  I’ll need to figure that out. It could be an encoding problem  or a 
hardware problem. George and I are going to compare settings between our  two 
servers, hopefully in the next day or so.

Change #1 will be done NOW. Expect the ITTY feed  to drop for a moment.

If you have time, could you test?

73,
Paul, W2TTY

On Jul 14, 2016, at 6:03 AM, Jack <_wa2hwj at att.net_ (mailto:wa2hwj at att.net) 
> wrote:

Paul,

Larry’s observation might be  contributing to my problem with
the Arvada ITTY feed. I get Sequim  ITTY solid, but your feed keeps dropping
out. Maybe a little more audio  would help?

73,
Jack K2TTY

From: GreenKeys [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of 
Larry Goga
Sent: Wednesday, July 13, 2016 10:54  PM
To: Paul Heller  <_paul0926 at comcast.net_ (mailto:paul0926 at comcast.net) >
Cc: Greenkeys <_greenkeys at mailman.qth.net_ 
(mailto:greenkeys at mailman.qth.net) >
Subject: Re: [GreenKeys] ITTY from Arvada  testing

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/ 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

=

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