[ARC5] ARC-5 TX problem --DC on fils gives hum on signal?

[Kenneth G. Gordon]

On 9 Oct 2009 at 12:26, J. Forster wrote:

> Maybe a ground loop with your supplies? Or possibly a transformer near
> something sensitive?

Several times in the past, I have experienced hum from a DC supply 
caused by the solid-state diodes themselves.

As I remember it, this problem is caused by the diodes switching 
"off" very sharply.

In those cases in which I had this problem, I fixed it by connecting a 
0.1 mfd, or so, disk-ceramic capacitor directly across each diode, 
and by bypassing each end of the diode string to a common point.

This MAY not be your problem, as there are any number of causes 
for such things, but it is something to be aware of.

Ken Gordon W7EKB