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Author Topic: Choosing a power supply ??  (Read 1966 times)

Posts: 17

« on: May 06, 2003, 10:07:08 AM »

as long as the rating is the same, what is the difference in using a switching vs. a non-switching (linear?) type power supply?  this is assuming that the switching supply is a quality, low-noise unit (per the QST review, something like the astron SS25).  there clearly is a size and weight difference but what else?

my needs are modest at present (ten tec scout), but i'm considering buying one supply now that could also power a 100W rig later as opposed to ending up with two (little p/s now, larger p/s later).

i appreciate any input and suggestions!

Posts: 21636

« Reply #1 on: May 06, 2003, 12:22:17 PM »

Difference in "using" a switch mode vs. linear power supply: Nothing.  DC is DC, and either design converts AC to DC, and your rig won't know the difference.

The difference you might note, however, is in the radiated or conducted noise generated by the power supply -- noise that you could hear in your receiver, especially a sensitive HF receiver.  If you choose a switch mode supply that has been rated "good" for use around amateur radio equipment by an independent testing agency (such as the QST product reviews), you're probably in good shape.


Posts: 2729

« Reply #2 on: May 06, 2003, 01:14:57 PM »

Since switching regulators are generally more efficient than series or shunt regulators, it is possible that a switching supply could supply the same power with less current draw from your AC line.  (Compare the specs carefully.)  This could be an important consideration, depending on the fuse/breaker size on your AC line, and what else you have connected to the same circuit.  My preference is the old-fashioned type supply, though, because I don't want to have to worry about the potential RF hash problem that Steve mentioned.

Posts: 1633

« Reply #3 on: May 07, 2003, 07:49:46 AM »

I've used a couple different brands of switching supplies and, of course, the usual Astron non-switching units.  If you NEVER listen to AM broadcast radio in your shack, then you likely won't be bothered by "noise" signals from a switching supply.  However, some of these supplies radiate substantial signals below 160 meters, enough to make it just about impossible to listen to the BC band.  While many articles and users talk about the "hash" from these supplies, it's my experience that they radiate mostly discrete signals, not random "hash".  I currently use an Alinco DM-330MV, which includes a front panel "noise offset control".  What this control really does is allow you to roughly vary the frequency of the discrete signals that the supply radiates.  Thus, if you find a power supply signal interfering with a desired BC band station, you simply rotate the "noise offset" control to move the offending signal off the frequency.

I've never experienced any noise signals from the Alinco nor my previous Astron switcher in any of the ham bands.  My low band antennas are some distance from the shack and are fed with underground coax, probably helping to eliminate any power supply noise problems on those bands.


Posts: 5

« Reply #4 on: May 16, 2003, 02:06:00 PM »

If you'd like information regarding the noise generated by switching power supplies, check out the the "Product Reviews"/"Power Supplies" section on this website.  A lot of the low rated switching power supplies generate noise, chirps, birdies, hash (whatever you want to call it), especially at 7.0 MHZ and below.

Posts: 2415

« Reply #5 on: May 19, 2003, 01:56:30 AM »

And just because you can't  hear it, Does not mean it
is not there..... (Noise)   Switching type power supplies when they go bad really add to the local
RF "Noise level"   And they do go bad.......
Consider the old faithful Marine deep cycle battery
and an automatic battery charger. Keeps equipment going
right thru the power failure or brown out, Usually costs less overall than a high quality Power supply,
And if you are in a good sunlight location, Great for
Solar power!
If a battery type supply is out of the question,
The old standard that most all power supplies are measured against is the Astron non-switching type.
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