Linear Or Switching Power Supply?

Discussion in 'General Technical Questions and Answers' started by KT4JX, Mar 29, 2008.

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  1. KT4JX

    KT4JX Ham Member QRZ Page

    I'm looking to get a new power supply, preferably 35 amp. I've heard Astron are the best? I see there are switching and linear varieties but I don't know the difference. Which one is better?

  2. AG3Y

    AG3Y Guest

    Switching power supplies were covered in detail in a couple of the League's QST magazine this past year.

    Briefly, there is very little difference between the various switching power supplies from the "brand-name" suppliers. But the difference between switchers and linear designs is a matter of weight, efficiency, heat buildup, etc. A switcher, because it runs at a very high frequency which is created by oscillators inside the supply will be cooler, lighter, and more efficient all around. However, it is possible that they can generate noise ( due to the switching action ) that can be picked up by the radio they are powering. Unless you are really reaching down into the noise level to pick up your stations, that more than likely will not be a problem. Again, we are talking about the higher quality name-brand supplies.

    Astron 35 amp supplies have been a very reliable standard for many years. But I do believe that you are thinking of the linear design rather than a switcher when you talk about Astron supplies.

    You will probably hear more from some of the real P.S. experts.

    73, Jim
  3. N2RJ

    N2RJ Ham Member QRZ Page

    Switching gives you smaller size and lighter weight, as well as better regulation and filtering (in most of them).

    I have had good experience with the Jetstream JTPS28. I've heard of one other ham (KC9ECI) who had a bad experience with another model jetstream, but I have not used that model so I can't really verify.

    I don't really detect any noise from it either, but with some of them it is a problem.

    Linear supplies are bigger and heavier, and some aren't that good with regulation and filtering. But they have less noise than most switching models and are also easier to troubleshoot and repair.
  4. KC9ECI

    KC9ECI Ham Member QRZ Page

    Ryan isn't kidding when he says I had a bad time with a Jetstream, but like all things, what works for some won't for others and vice versa. I've also been using an Alinco switching power supply for a few years now and I'm happy with it.
  5. N0WVA

    N0WVA Ham Member QRZ Page

    Which makes more sense sitting beside a receiver that is sensitive in the microvolt range? A nasty switching supply that is throwing hash all over the place, or a nice clean linear supply that has no miniature harmonic transmitters running to make hash?
  6. KT4JX

    KT4JX Ham Member QRZ Page

    Thanks for the replies. I'm considering an Astron RS-35M which has good reviews on eHam. I had a bad experience with the cooling fan on a Pyramid 35 amp power supply a couple years back. The fan would come loose off the shaft after every 20 hours of use or so. I had to keep opening the thing and repositioning the fan.

    Hopefully I can forget about the fan with the Astron.
  7. N2RJ

    N2RJ Ham Member QRZ Page

    A nice clean, well filtered switching supply.

    I frequently work QRP stations and low powered, wet noodle DX like 3Y0E when my friends in the area can't even hear him.

    Of course I have a better antenna and location, but my power supply doesn't seem to be negatively affecting my radio one bit.
  8. VA2GK

    VA2GK Ham Member QRZ Page

    I have a 14V 50A switching supply that is terrible for noise and harmonics.
    I have used Astron switching PSUs with no problem at all.

    If you pay for quality you won't have noise because the units are filtered and the designers are conscious about RF interference. If you buy cheap units like computer stuff or supplies that were not intended to be used in a critical radio environment you will more likely have QRM.

    (instructions on how to make 13.8V supplies out of old computer supplies is all over the net, with the obvious results)

    Of course a linear, even a badly designed one will be quiet as a whisper.
  9. WA9SVD

    WA9SVD Ham Member QRZ Page

    The Astron RM-35's don't HAVE a fan.
    But be aware that the RM-35 has a 35 Ampere PEAK rating; it's only 25 Amperes continuous duty. It can make a big difference in some cases. If you really need 35 Amperes, you should look at the RM-50 supply.
  10. KC9IUX

    KC9IUX Ham Member QRZ Page

    I love the Astrons.

    I've had a bunch, had three 35M's in parellel for a bit.

    I have fewer now, the ground in my meter box at a former home went south, sending 220 to them, but most survived.
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