Use of PC power supplies with K2

[Kenneth Moorman]

I would like to hear from anyone who has attempted to use one of the small
external PC AC adapter power supplies with a K2.  They are, of course,
switchers, so I am not very hopeful.  I have found a couple of possible
candidates, one a Meanwell P40A-4PSJ rated at 13.8 volts at 2.66 amps and
the other an APS AD-740U-1138, rated at 13.8 volts at 2.8 amps.  They seem
to have somewhat comparable specs as to regulation, ripple, and protection.
I suspect they would be pretty bad on RFI, so even though they can be had
cheaply, they may not be worth the grief.  My fallback position would likely
be the little unit from Gamma Research, HPS-1a, but that will be twice as
heavy and probably ten times more expensive....but from what I've read about
it, it is not very noisy electrically.  I would really appreciate any
thoughts, especially those with first hand experience.  This would only be
for portable operation, not "normal" use.  Thanks.

73,

Ken Moorman, NU4I

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[John Ragle]

  Ken...

     The general subject of RFI/switching power supplies has been
bruited about on this list server several times. I personally have had
excellent experience with the several that I use. These include a 20
amp, 13.8 V supply from pyramid and two 25 amp, 13.8 volt supplies from
Radio Shack. These supplies sit within inches of my K3/100 and my ICOM
910H and cause no interference that I can detect.

     On the other hand, I have a circline fluorescent lamp with a
magnifier that I transplanted from my workbench to my operating site,
about which I made the following discovery. The lamp itself runs off a
power supply at the base of the "tensor" arms. Turning the lamp on and
off produces no change in interference, but unplugging the lamp from the
wall outlet reduces hash noise on 20 meters by about 3 S units !!!. The
wall-wart-like power supply in the base of this lamp is very noisy, and
the lamp has accordingly been banished to a less sensitive site.

     My summary comment would be that power supplies run the gamut wrt
RFI problems, and that one might well have to proceed by
trial-and-error. I have always rejected use of the PC-type power supply
because they usually come with a spaghetti of different wires intended
for different functions within the computer. The small Radio Shack 25
amp supplies are about the same volume as a typical PC supply, and a
great deal more congenial (cosmetically) than the latter.

John Ragle -- W1ZI

=====

On 10/3/2010 1:47 PM, Kenneth Moorman wrote:
> I would like to hear from anyone who has attempted to use one of the small
> external PC AC adapter power supplies with a K2.  They are, of course,
> switchers, so I am not very hopeful.

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[Bob Nielsen-2]

I have used the MFJ-4103 (13.8 v, 2.89 amps) with my K2 and haven't noticed any switching noise issues.

Bob, N7XY

On Oct 3, 2010, at 10:47 AM, Kenneth Moorman wrote:

> I would like to hear from anyone who has attempted to use one of the small
> external PC AC adapter power supplies with a K2.  They are, of course,
> switchers, so I am not very hopeful.  I have found a couple of possible
> candidates, one a Meanwell P40A-4PSJ rated at 13.8 volts at 2.66 amps and
> the other an APS AD-740U-1138, rated at 13.8 volts at 2.8 amps.  They seem
> to have somewhat comparable specs as to regulation, ripple, and protection.
> I suspect they would be pretty bad on RFI, so even though they can be had
> cheaply, they may not be worth the grief.  My fallback position would likely
> be the little unit from Gamma Research, HPS-1a, but that will be twice as
> heavy and probably ten times more expensive....but from what I've read about
> it, it is not very noisy electrically.  I would really appreciate any
> thoughts, especially those with first hand experience.  This would only be
> for portable operation, not "normal" use.  Thanks.

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