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Author Topic: Linear vs switching PS for noise  (Read 2630 times)
K0YHV
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Posts: 179




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« on: August 24, 2012, 01:15:59 PM »

I have been using a Jetstream switching PS for the past few years, but have been thinking about switching back to an Astron linear PS because it might be quieter RF hash wise. Has anyone had a chance to compare the noise a switching PS generates compared to a linear PS?  Would it quiet the noise floor much in most cases?
 
John AF5CC

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AA4PB
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« Reply #1 on: August 24, 2012, 03:14:21 PM »

Switching suppies, when they generate hash, generally create it in fairly narrow ranges of frequencies rather than raising the overall noise floor. I you don't notice it then its probably not generating much noise. The biggest problem is for those who have the antenna close to the power supply or have a common mode pick up problem on the coax. I've not had any noise problems from the Icom or MFJ switchers that I have in the shack. I also have an Astron RM35 linear supply and I don't notice any difference between them (as long as I don't have to lift them).

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K0YHV
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« Reply #2 on: August 24, 2012, 04:42:22 PM »

That is good to know. I do have some sweeping type noises from time to time on the ham bands, but I don't know if it is from my PS or from something else.

John AF5CC
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ONAIR
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« Reply #3 on: August 24, 2012, 04:54:10 PM »

That is good to know. I do have some sweeping type noises from time to time on the ham bands, but I don't know if it is from my PS or from something else.

John AF5CC
   Some switchers do generate noise.  I have had no issues with my Jetstream switching power supplies.
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AA4PB
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« Reply #4 on: August 24, 2012, 06:29:41 PM »

Oh, virtually all of them generate some noise (RF hash). As you put greater separation between the power supply and the antenna, the weaker the noise is at the receiver. At some point it is overtaken by the band noise and no longer heard.

As I said, I don't pick up any noise from the switchers - but then my tower is about 100-feet away from the shack where the power supplies are located.

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KL2EC
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« Reply #5 on: August 24, 2012, 09:29:59 PM »

I noticed a LOT of noise from two different switching supplies that went away after going back to a linear.  Don't think I'm too close to my antenna, either.
                                kl2ec, Mark
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KH6DC
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« Reply #6 on: September 07, 2012, 11:50:42 AM »

I noticed a LOT of noise from two different switching supplies that went away after going back to a linear.  Don't think I'm too close to my antenna, either.
                                kl2ec, Mark

What linear did you choose? 

I have a Astron SS30 and it works fine with no noise.  My plasma TV generates all the noise.  My tower is 50ft+ away with the hex up 35ft.  My BigIR is 30ft away and both don't pick up noise from the switcher.
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73 and Aloha,
de Delwyn, KH6DC
NR9R
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« Reply #7 on: September 07, 2012, 02:00:05 PM »

As others have mentioned, the noise can depend on how close the antennas are.  In may case, I have a small lot with my shack only about 30 ft from my vertical and I could hear noise on my Samlex SEC-1223.  When the capacitors failed after a year I started researching other switching supplies and could not find convincing information that other models are any more quiet. 

There are QST reviews suggesting that many supplies have pretty good noise filtering under high current load and no-load conditions.  However, I remember also finding some other testing that showed some supplies peaking in noise undo loads of a few amps, close to an HF transceivers receive current.  If you search the web you will also find modifications for improving the noise filtering for most popular switching supplies, so that tells you something.

The other complaint people have about compact switching supplies is the acoustic noise from the cooling fan.  There are many mods out there for improving that too.

In the end I decided to just go back to a reliable Astron linear supply.  I'm glad I did because the few dollars you save with a small switching supply was not worth the other hassles for me.  It just sits under my desk unnoticed and will likely keep working for decades.  I bet if I replaced the capacitors every 20 years and kept the cabinet from corroding it would keep working indefinitely.  I don't have the same confidence with a switching supply.
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