[GreenKeys] Distortion Testing of my AN/FGC-25

[Don Sentz via GreenKeys]

It was great to receive all the positive feedback regarding my teletype set, many thanks to all of you who wrote to me. I am very grateful to know so much more now, about the history of this set.

After my last posting about my AN/FGC-25 teletype set, I developed a program for my microcomputer to sample the current loop at approximately 10 kilosamples per second. It starts storing samples upon detecting a mark-to-space transition. It then dumps the data buffer to the Win7 laptop PC, where I then port the data into MS Excel for plotting and analysis. The data buffer captures about 5 characters' worth of signal at 60wpm.

I wrote a report that includes plots of some of the data I took a few days ago. I posted it for viewing and .pdf download at 
https://www.scribd.com/doc/270450987/Distortion-Testing-of-My-AN-FGC-25-Teletypewriter-Set

As evident in the report, both the keyboard and the tape reader appear to be suffering from frequent "glitches" in the mark signal that occur shortly after space-to-mark transitions. There were some data captures where no glitches occurred at all. It is quite puzzling to me. Adjusting the contact spacing did not seem to matter much (except for affecting the bias performance).

Any feedback and advice regarding these glitches would be most appreciated.
                                                                   -------
I also posted a two-chart file that shows the result of adjusting the keyboard contact spacing slightly;

https://www.scribd.com/doc/270451314/Keyboard-Results-Comparison

To do the comparison, I recommend that you download the chart set and open it with your .pdf reader. Use your up/down or left/right arrow keys to flip back and forth quickly between the two charts, to get an animation effect.

-73
Don