Switching power supplies...yet another comment

[Edwin Johnson]

Guess I have to add to the mix by saying I bought several years ago an
MFJ-4125 25 amp switching power supply (the one without the meters and about
6"x6"x2", or so) for portable use. I did a bit of research and at the time I
bought it, the hash and output was smoother than anything on the market. (That
sounds hard to believe, doesn't it? hi)

At any rate, absolutely no noise nor hash of any kind and I usually use random
wire or end fed zepps for portable.

There have been some new introductions since then to the market which may have
other advantages, but I will say this is an excellent choice at a fair price.

> Date: Sat, 17 Jul 2010 06:47:59 -0400
> From: John Ragle <[hidden email]>

>      I have several inexpensive 25-amp switching supplies from Radio
> Shack and Pyramid. I also have a couple of "linear" supplies that are
> built like the battleships of yore, and some gel batteries for portable
> operation.
~
> John Ragle -- W1ZI

73 ...Edwin, KD5ZLB
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[Alan Bloom]

I can second that.  With no antenna connected I can hear some spurs on
the lower bands, mainly 160 meters and a little on the other low bands,
but with the antenna connected, band noise covers them up completely.

The only complaint I have heard about the MFJ-4125 is that, while it is
electrically quiet, acoustical noise is another matter.  The internal
fan is rather noisy.  I designed a proportional fan controller to slow
the fan down under normal operation and speed it back up again if the
supply gets hot (say for continuous-duty RTTY operation).  The article
was in February 2010 QST.

Al N1AL


On Sat, 2010-07-17 at 20:25 -0500, Edwin Johnson wrote:

> Guess I have to add to the mix by saying I bought several years ago an
> MFJ-4125 25 amp switching power supply (the one without the meters and about
> 6"x6"x2", or so) for portable use. I did a bit of research and at the time I
> bought it, the hash and output was smoother than anything on the market. (That
> sounds hard to believe, doesn't it? hi)
>
> At any rate, absolutely no noise nor hash of any kind and I usually use random
> wire or end fed zepps for portable.
>
> There have been some new introductions since then to the market which may have
> other advantages, but I will say this is an excellent choice at a fair price.

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