[GreenKeys] ITTY from Arvada testing

[epvgk at limpoc.com]

On Wed, Jul 13, 2016 at 08:54:19PM -0600, Larry Goga wrote:
> 
> 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.

The input impedance is pretty high, around 20k ohms, and it's not picky
about signal level. 


> 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.
> 

I've had it going for several days now into an ST-6 and it's looking 
pretty good. I'm not sure what to make of the breaks I keep seeing. 
Maybe it's not an analog problem but generated by the text rendering
process? 

example: (everywhere it says [BREAK], the output from the ST-6 spaced
longer than a character time) I'm not convinced this was from
dropped audio in every case. 

NOAH IS CURRENTLY A SOPHOMORE AT THE UNIVERSITY OF CINCINNATI AND THE
CURRENT STATE PRESIDENT OF NAACP YOUTH AND COLLEGE DIVISION FOR
OHIO.(PHOTO: SAM GREENE)

CINCINNATI [BREAK] NOAH SHERMAN IS A BIG YOUNG MAN WITH ADARK BROWN COMPLEXION.[BREAK] HE KNOWS WHAT THAT[BREAK] MEANS WHEN HE GOES OUT INTO THE WORLD.

"I AM PERCEIVED AS SCARY," SAID SHERMAN, WHO AT 19[BREAK] STANDS 6-FOOT-7[BREAK]
AND WEIGHS 260 POUNDS. "I HAVE TO COME INTO A ROOM WITH A
SMILE. I HAVE TO BE JOLLY. OTHERWISE,[BREAK] I AM SEEN AS THE MENACING AND
ANGRY BLACK MAN."


eric.