[GreenKeys] Loop Supplies

[Lee Mushel]

Some things never change.   In 1960 the loop transformer of choice was the Triad N-48X.   Mouser has 20 in stock but I will admit it costs more now: $14.
The one I'm holding in my hand cost $1.50.....  I used to use a full wave bridge since they were conveniently available at an electronics emporium close to home.
73

Lee   K9WRU
  ----- Original Message ----- 
  From: Jack 
  To: greenkeys at mailman.qth.net 
  Sent: Wednesday, June 17, 2015 5:52 PM
  Subject: [GreenKeys] Loop Supplies


  ZCZC

   

  Everyone should have a reliable and available loop

  supply for testing TTY's, etc.

   

  I have been using Hammond 187C120 transformers

  which can be obtained from Mouser Electronics for

  around $10.00, plus shipping. This transformer outputs

  120V at 100 milliamps and has a small physical

  footprint. Higher current ratings come with higher

  cost.

   

  All you need is a diode, electrolytic filter capacitor

  and a current limiting resistor and you have

  a "loop supply". I use a 1N4007 diode, 40 mfd 450V

  capacitor and an adjustable wirewound resistor of

  approximately 2,000 Ohms for a 60 ma. loop.

   

  Jack K0TTY

   

  NNNN

   

   

   

   



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