Power Supplies, RF quiet, Linear or Switching?

W5lz

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Feb 28, 2019
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Lately, switching power supplies aren't as noisy as they used to be. I have had several that didn't make any noise. I can only remember having one that did make noise but that was a lot of years ago. One source you may not have thought about is the places that supply RV builders. They have AC to DC power supplies for the RVs that need them. They are typically 'larger' than what you normally find on the ham markets, 55 amps isn't unusual at all. Be warned though, they are not 'pretty'! But since it's usualy stuck under a desk, who cares?
 

SuperG900

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Just got my order in from powerwerx - everything was nicely packed. I bought the AT-578, the radio frame, power supply and an external speaker. Very very nice stuff. Waiting on coax from another vendor.
 

JoshuaHufford

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Just curious, has anyone ever checked the quality of power from a PC power supply? I ran across this the other day and thought it was neat,


I know you couldn't power a lot from this, but I don't transmit, just receive with my radios.
 

N4KVE

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PALM BEACH, FLORIDA
Several years ago I was involved in a project to upgrade the FW, & FC in 1200 APX radios. Instead of bringing an Astron PS, or something similar, the boss brought a computer PS that was the size of a half loaf of bread. He had 5 power cords coming out the back to power 5 radios at the same time. It worked great.
 

WB9YBM

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Niles, IL
Just curious, has anyone ever checked the quality of power from a PC power supply?
I'm assuming they've got to be pretty clean to make sure no hash can accidentally be seen as a random digital data bit by the CPU, and I have heard some hams using PC power supplies successfully, although I haven't tried it myself first-hand.
 

prcguy

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So Cal - Richardson, TX - Tewksbury, MA
Yes and most are unusable for HF radios. A friend of mine had a writeup many years ago in one of the major hamster magazines on how to reduce the noise hash from computer power supplies. He found the LC filtering in all computer supplies at that time were installed backwards to keep noise out of the power supply and not to reduce noise leaving the power supply.

Just curious, has anyone ever checked the quality of power from a PC power supply? I ran across this the other day and thought it was neat,


I know you couldn't power a lot from this, but I don't transmit, just receive with my radios.
 

JoshuaHufford

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Yes and most are unusable for HF radios. A friend of mine had a writeup many years ago in one of the major hamster magazines on how to reduce the noise hash from computer power supplies. He found the LC filtering in all computer supplies at that time were installed backwards to keep noise out of the power supply and not to reduce noise leaving the power supply.
What about VHF or higher?
 

rja1

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I've had an Astron 30 Amp linear supply in my shack, running 24 / 7 since 1988. Only once in 32 years did I notice the voltmeter sitting at zero. It was right after a nasty thunder storm. A close by lightning strike caused the Astrons crowbar protection circuit to trip. A simple power cycle & all was well.
I've had a few switchers but they are all gone now. AM radio interference, HF interference, reliability were all issues. And the Astron supply just keeps working..............and working............................................................................
 

SuperG900

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You could probably get away something like, maybe a DC blocking cap into the antenna port on one of those SDR dongles and use that to peek at it - quick and dirty.
 

N4DJC

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I have an Astron SS18 for a 65 watt VHF mobile I use at home, the fan has never come on. I think I'm pulling maybe 10 amps.
 
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