[Elecraft] Switching P/S Horror Stories

[Ron D' Eau Claire]

> I have had noise problems with switchers as well.  What I want to
> know is "why
> is it so hard to filter/bypass these supplies to get rid of the noise?"
>
> I'm old enough to remember the advent of TVI and the development of TVI
> suppression techniques for homebrew and commercial rigs.  Why
> can't we take a
> similar approach to switching power supplies?
> Vic, K2VCO

Vic, you are right that it's a matter of shielding and filtering just like
the old TVI issues with Ham transmitters in the 1950's  - but the switching
power supply is putting out r-f that is probably thousands of times more
powerful than the harmonics from our old Ham rigs and we are using receivers
that are probably thousands of times more sensitive than the old TV's.

Take a 50 to 100 watt transmitter designed to produce broadband r-f right on
top of the TV channels, then set it right next to the TV set and connect it
to the TV with cables that depend upon filters to stop ALL of the r-f, and
you will see just how unsuccessful the system would work to prevent TVI.

That is essentially what we have with "switcher" power supplies in the shack
and connected to the rig.

I think that it's AMAZING that they have managed to make them as 'quiet' as
they have.

Ron AC7AC
K2 # 1289