[GreenKeys] ITTY from Arvada testing

[Larry Goga]

God Morning Paul,

I just received your email at a little after 9:00AM MDT.  Here are the results of measurements made just now.

The ITTY signal from Sequim, WA still reads -28 dBm into 600 ohms.  That’s a good thing as that’s the reference.

The Arvada, CO signal has come up -32 dBm.  Now only 4 dB down from ITTY.  

I do not have the time to test decoding right now, but I will later this afternoon and report to you what I see.

I did notice one thing yesterday.  To me it looked like there were some character translation issues with your stream.  I was seeing quote marks ( “ ) printing on my M28, with whatever typebox this is, as a string of three question marks ( ??? ).   From Sequin I would get a quote mark.

Also, from Arvada an apostrophe ( ‘ ) would print as three spaces.  No problems with apostrophes from Sequin.

Hope this helps.

73,

Larry, AE5CZ

> On Jul 15, 2016, at 8:17 AM, Paul Heller <paul0926 at comcast.net> wrote:
> 
> 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 <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/ <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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