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

[Dennis Monticelli]

The ground loop theory seems to be most likely.

One experiment you could run is to use a 12V battery to power the filament.
That is a floating power source and thus no ground loop (or rectifying
diodes) involved.

Dennis AE6C

On Fri, Oct 9, 2009 at 12:48 PM, Kenneth G. Gordon
<kgordon2006 at verizon.net>wrote:

> 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
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