[Elecraft] Audio transformers needed

Jim Brown jim at audiosystemsgroup.com
Sun Jul 7 11:55:14 EDT 2013


On 7/7/2013 12:10 AM, Jim Wiley wrote:
>
> These will be used to remove a ground-loop problem between my computer 
> and other equipment.

You do NOT need a transformer.  What you DO need is simple bonding.

http://audiosystemsgroup.com/HamInterfacing.pdf

There are two simple steps.

1) Get power for all of the radio equipment, and for all equipment 
connected to your radio equipment (computer, computer monitor) from the 
same 120V electrical outlet.

2) Bond from chassis to chassis of all equipment that has an unbalanced 
signal connection to your radio equipment (rig, computer, audio 
processing, etc.) with short, fat copper. I use the braid stripped from 
good transmitting coax (RG8), which is typically the equivalent of #10. 
And, of course, add a short fat bond from the rig to the station ground.

That's all you need. A chassis connection to most laptops can be found 
at the connector retaining screw of DB-connectors (SVGA, LPT, RS232).

There is, by the way, no such thing as a "ground loop." The REAL cause 
of the problem is simple leakage current within the AC power system. See 
the link above for an explanation.

73, Jim K9YC


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