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Convert PC Power Supply for C.B use?

Discussion in 'Home Brew' started by T23, Oct 18, 2010.

  1. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    The power supply will only put out what the load draws. Do you know how much the device is supposed to draw? If you are concerned about the power supply being too light check the fuse in the device you want to power. In order to measure the current you need an ammeter to measure amps drawn. A typical multimeter usually only measures a couple amps, maybe up to 1o on some models.


     

  2. KJ6HYC

    KJ6HYC Member

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    Not understanding "standard equipment". Do you mean test equipment? To measure the output current you would need test equiptment, a DC ammeter with the appropate range.
     
  3. unit_399

    unit_399 EL CAPO

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    There is no reason for not using a pc supply as a power source for communications equipment. Since the power rails are clean, the only problem could be from radiated rf generated by the switcher. Unless you're using the supply to power a handheld, where the rubber duck antenna is near the supply, or you do something stupid (like sitting the transceiver on top of the supply), there won't be a problem because the radiated rf is negligible if it is within fcc mandated limits.

    Use a good quality supply, and place it a couple of feet or so from your equipment. Install bypass caps on supply lines as close to the equipment as possible. There are several sites online that explain how to convert a pc supply to bench use (including adjustable output voltages.)

    I piggybacked four 500-watt pc supplies and use them to power my 5-pill with no problems.

    - 399
     
    #18 unit_399, Oct 27, 2010
    Last edited: Oct 27, 2010
  4. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Ummm well yes but that may well be fine on 11m where the antennas are often located far from the shack and the frequency relatively high but in some cases where hams like myself have end fed wires where the antenna actually enters the shack, pick up can be a real problem. Also the noise pick up is MUCH greater on 160m and 80m than it is on 11m. Limits or not many switcher supplies radiate a very strong signal. Did you see my comment about the washer and dryer problem I have? The dryer is in the basement and the nearest antenna is about 50 feet away. I suspect some of it is being re-radiated from the AC wiring. Either way for my MRF-151G project it would have taken about 8-10 supplies and that was going to be too much to bother with. I suspect the noise would have been dreadfull on the low bands as all the supplies I have are at least 10-12 years old and have NO filtering at all.
     
  5. unit_399

    unit_399 EL CAPO

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    CAPT K.-

    I agree 100%. But the original thread asked about using a pc supply to power a CB which was the reason for my answer. 73s-

    - 399
     
  6. smith562

    smith562 Member

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    convert pc power supply to 13.8v

    Best site I have found is this one, you do need some electronic knowledge though
    http://www.qsl.net/vk4ba/projects/ps.pdf

    a pdf file, explains fully how to do it
     
  7. unit_399

    unit_399 EL CAPO

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    :oops:

    I think I was a little premature with my post that it was OK to power a CB from a PC supply. While I still think that the radio would be unaffected by the rf generated by the switcher circuit in the supply, I got to thinking that maybe the rf generated by the transmitter could screw up the switcher. I use switching supplies to power my 5-pill and even with the amp set to high, the supplies' output voltage is rock steady. But... I carefully grounded and shielded everything.
    As an experiment, I put my dummy load next to a converted pc supply that I use on my bench. When I keyed 200 watts into the load, the supply's output voltages started jumping all over the place. I know this is an extreme test, but it shows that there can be problems. Just something to be aware of.

    - 399
     
  8. mackmobile43

    mackmobile43 Jock Supporter

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    The cb's voltage regulators should last longer using these weak power sources if they manage to hold voltages.
     

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