[ICOM] Computer Control Interface

[Doug Faunt N6TQS +1-510-655-8604]

   Date: Tue, 27 Dec 2005 19:56:41 +0000
   From: Jerry Flanders <jeflanders at comcast.net>

   Comment: There are several different optos available, with different 
   "gain". Just use one that has sufficient "gain". Also - slightly 
   increasing current through its LED by slightly reducing the 
   resistance of the current-limiting resistor also would help to insure 
   if keying is marginal. Verify capability of your serial port line 
   before you get wild with this.

   Jerry W4UK

   At 17:42 12/27/2005, Gary wrote:
   >Bob,
   >
   >I was looking at the MFJ-1279 schematic and the CW out is using a 
   >Opto Isolator. In the past I remember an Opto isolator not being 
   >able to place a hard enough ground on the Icom UP / Down input.

There are items sold as "solid-state relays" that are essentially an
optoisolator with an FET output.  They can provide very low output
levels, even at high currents.
Look for a NEC/CEL PS710 and similar items.

73, doug