[GreenKeys] CRT Question

[Ralph Mowery]

Many of the TUs have a low voltage output for the mark and space tones.   

You will not see a single line, but an eliptical display (football shape) with the vertical width depending on how shape the mark/space filters are.  

The display may not be exectally horizontal and vertical when tuned in correctly depending on how well the filters are on frequency and a few other factors.

If you have an oscilloscope, you will not use the internal time base.  YOu use the horizontal input for the mark and then hook the vertical input for the space.

There is no reason the mark/space can not be reversed on the scope, but that is the way it is usually done.

YOu do not use the mark/space pulses, but the audio tones comming from the filters.

  ----- Original Message ----- 
  From: Keith Densmore 
  To: greenkeys at mailman.qth.net 
  Sent: Thursday, August 20, 2015 10:28 AM
  Subject: [GreenKeys] CRT Question


  Time for another question......

  My Dovetron  MPC  1000 has an LED crosshair tuning display, which works just fine but.....

  I have a couple of spare o'scopes here and I really like the kind of display that shows mark/space and noise. Tuning is correct when the display shows vertical/horizontal tuning of mark/space



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  .

  This type of display was used on some older TU's I have seen and that tuning method is also used on MMTY.



  Question is how is that type of display wired into a terminal unit?  It's no problem picking off mark/space pulses but how do you make them display as the 'ball of noise'?



  Thanks,

  Keith




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