Re: 12v DC power supply question

Christopher Erickson

Modern switching power supplies use a frequency of about 20Khz to 2Mhz
instead of the old-school 60hz to change voltages from one level to another.
The higher the frequency, the smaller the transformer and filter components
can be. This saves in weight and cost and can increase conversion
efficiency, resulting in less heat generation (energy loss).

The down side is that the switcher frequency range is in the medium-wave &
shortwave radio spectrum bands and can cause primary and harmonic
interference for ham gear at certain frequencies placed close to the
switcher. Having a switcher with an adjustable frequency is sort of a cool
feature that would really appeal to ham radio enthusiasts and shortwave

-Christopher Erickson
Observatory engineer
Summit Kinetics
Waikoloa, HI 96738

-----Original Message-----
From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, October 19, 2017 5:34 PM
To: A-P GOTO Mounts Yahoo Group
Subject: [ap-gto] 12v DC power supply question

Recently somebody (I think it was Roland) suggested that what we want is a
good quality regulated SWITCHING power supply.

Why a SWITCHING PS instead of an old-fashioned transformer PS? I thought
that even though transformers are much much heavier and larger, they were in
general cleaner.

The 12v PS I used to use with my Mach1 and camera was made by Pyramid --
with a very heavy transformer inside. A couple of years ago I put that one
in my mobile observatory -- where it is now. And I bought a second one just
like it for portable use with my Mach1 and camera.

But that "new" PS has a serious problem (I mentioned in another post this
evening). So I bought a new switching PS. I like the new one because it's
so much smaller and lighter and has built-in PP connections. But it has a
"noise adjuster" knob to hopefully minimize noise for HAM radio use. The
fact that it even has such an adjustment tells me there's a problem with
noise in at least this switching PS.

Any comments?


Posted by: "Woody Schlom" <woody_is@...>

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