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Thread: Switched mode PSU and SSB/AM

  1. #1

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    Default Switched mode PSU and SSB/AM

    Just wondering if a switched mode power is suitable to use for an SSB rig? I just ordered a 30A one for my 2 metre - The power drawn for FM will be pretty steady, but I thought of getting another one for the HF radio, but just how would the PSU react to the constantly changing power requirement?

    This is the beast: http://www.banggood.com/Mini-Switchi...p-1017264.html (Yeah, I know it's "Made in China", but the main power switch for my bench is close to hand and so are the fire extinguisher and fire blanket...

  2. #2

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    My best guess is it should work OK. My only concerns would be noise and ripple. I am curious what you think of it after it arrives. 30A at under $20 delivered is impressive to say the least. Let us know how it works. A short review would be appreciated. I personally don’t need nor want another power supply. Over the years, I as most old hams end up with several but it might be nice to be able to suggest such a unit to the new ham or those who do not want the weight and expense of a linear supply.
    Joe KA9UCN

  3. #3

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    Quote Originally Posted by KA9UCN View Post
    A short review would be appreciated. ... it might be nice to be able to suggest such a unit to the new ham or those who do not want the weight and expense of a linear supply.
    Thanks for the thoughts. I was wondering about noise as well - The "smart" charger I use for the battery (my current "power supply") does introduce a little bit of noise, but at the moment it's acceptable. Once I become a QRP DX junkie, it probably won't be...

    Will do a write-up though!

  4. #4
    Super Moderator pmh's Avatar
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    I've used this one, from day one:-

    http://www.nevadaradio.co.uk/cb/cb-p.../nevada-psw-50

    with no noticeable additional noise.

    My biggest noise problem, to date, came from my Raspberry Pi 5 amp power supply.

    Kind regards,



    Phil

  5. #5

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    The beastie just came today. I have only given it a quick GO/NO-GO test: That is, plug it in - no smoke, good, hook up to rig, rig works and still no smoke - even better. But, as I'm off to the UK tomorrow, a proper test, for noise and such will have to wait until at least next weekend. I have also ordered a dual Volt/Ammeter (50 amps) for it. I got one (FSD 10 amps) for my old 12 V PSU and it works well:
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  6. #6

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    Well, that sucked...
    I ran the HF rig (Icom IC-735) first from the small power supply (5 A with transformer), receive only, as it wouldn't be enough to drive during transmit. Found a quite patch near 18 MHz - pretty quiet.

    Then hooked up the 30 A switched mode. Ugh!!! S5 to S7 noise! And that's with the power cable wrapped around a ferrite tube.

    I guess I'll be using it for the 2 metre rig then...

  7. #7

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    I had a bit better test today. I hooked the Icom up to a battery and switched everything else in the room off.
    The S-meter was pretty much on zero. I had a tune around, heard a few stations, some Morse and so on, and went back to a quite spot. S0.


    I plugged the power supply in and switched it on. After a few seconds, the S-meter climbed to S5, held a while then hit S7.


    I switched it off and the S-meter wound down to zero again. I did this a few times and got the same results each time.
    I then plugged the Yaesu 2-metre rig into the power supply and turned it on. The S-meter on the Icom climbed to nearly S9! 2-metre off, and the noise dropped. On again, and it hit nearly S9 again. Not good.

    I guess then the noise is conducted in to the mains wiring and radiated out from there.

    In comparison, the "generic" laptop PSU I have gives about S5 and the LED table light gives an on-off S5 chirp.

    Since the PSU was less than 20 Euros, I thought "Cry havoc and bugger the warranty seal!" and opened it up. I had read a few websites where they showed dodgy power supplies from China with missing filter circuits, transformers with a single loop of wire and a core of cement and so on, so I didn't bother holding my breath...

    Well, everything seems to be there:



    AC Input filtering


    DC Output filtering

    There are some places for for a few extra components, but I doubt they have anything to do with the noise.


    I am now waiting for the 50 A FSD ammeter to turn up, so I can put the thing in a better looking box and run the Yaesu 2-metre FM rig from it. Though I am now looking in knocking up some proper filtering on both the mains I/P and DC O/P, so that I can us it on with the Icom. [s]If that goes OK and the PSU works OK over then next six months or so, them I may get another one, so both radios have their own supplies.[/s]

    On second thoughts, to be honest, with the effort and extra money required to make it usable for HF SSB, I would NOT buy another one, rather save my pennies and buy a much better quality PSU.
    Last edited by OH8GAD; Wed 17th Feb 2016 at 12:48.

  8. #8

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    Been a loooong time since I did anything with this. During the summer last year, I got a mains input socket (OK, technically, it's a plug) filter (like the one in the attached image). I hoped it might reduce the mains-borne noise. Nope, no luck. I have read a few articles on how to filter SMPS DC output, which involve either buying more quite expensive bits or stripping them from a PC power supply - which I don't have.

    The upshot is, that I feel any more work on it will just be like throwing money onto a fire. It works OK for the 2 m FM rig now, but not good for the HF. I'll keep my eyes open for a car battery.
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    OK, so it's been over a year since my last post on this and over two years since I started it...

    Anyway, I'm giving up on it as a viable PSU for HF use. Despite the metal box and mains filter, the radiated QRM is still just as bad. So, it's junk.

    I'm now keeping my eyes open for a huge (salvaged) transformer which can handle 30 amps+ for a linear supply.

  10. #10

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    In the USA you can buy an Astron 35A Linear power supply any old day of the week at a hamfest for around $65.00

  11. #11

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    Quote Originally Posted by Sixmeters View Post
    In the USA you can buy an Astron 35A Linear power supply any old day of the week at a hamfest for around $65.00
    But I don't happen to be in the US...

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