[GreenKeys] Basic Loop supply

[Ralph Mowery]

For the local loop 48 volts should be enough for good copy.   

 

Now we are getting somewhere, simple and inexpensive.  I think that was the original  idea of that thread.

 

 

From: Gil Smith [mailto:gil at baudot.net] 
Sent: Wednesday, May 18, 2016 9:08 PM
To: rmowery28146 at earthlink.net
Cc: greenkeys at mailman.qth.net
Subject: RE: [GreenKeys] Basic Loop supply

 

I like these little 48V supplies:

http://www.mouser.com/Search/ProductDetail.aspx?R=RS-25-48

 

Less than $14 each for a nice little enclosed 48VDC, 0.57A switcher that does 115/230-in -- just add a line-in jack, fuse and switch on the AC side.

 

Then add an 800-ohm 5W resistor (just over a buck) for 60 mA loop:

http://www.mouser.com/Search/ProductDetail.aspx?R=25J800E

It will only dissipate 2.9W.

 

Though I think just 48VDC is plenty, folks always argue the point.

 

A 96V loop is easy enough:  use two of the 48V supplies in series and then use two 800-ohm 5W resistors in series, or get a 1600-ohm 10W.

 

easy-peasy.

 

 

gil smith, AF7EZ
greenkeys moderator
gil at baudot.net

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