BKA (TA2RX) asked: I have got a MeanWell SP320-15 switch mode power supply. I found the specs at <http://www.computronics.com.au/meanwell/sp-320/> after a Google search. This page specifies it at 15V and 0 to 20.0A at plus or minus 1 % tolerance, 150mV R&N (whatever that means) and 86% efficiency. However, after reading all the different industry (and non-industry) standards I got all confused.
There are some more specs on the page but could not figure out what they mean. BTW I had mine set to 13.8 V. So, theoretically this should enable more current to be withdrawn. The question is how much current this thing can supply for HAM purposes (including RTTY, PSK31, etc.)? ----------------------------------- The specifications sheet says 20 amps at 15 VDC. The current may not go up because you are limiting the voltage to 13.8. It depends upon the circuit. In any case, it would not be much higher. Without any other comments, I would assume the ratings are continuous duty, which is typical for computer type power supplies. That does not mean you can get away with drawing more current than 20 amps at peak, however, since it has over-current protection. It doesn't say at what current the protection circuit shuts the supply down They don't provide intermittent (ICS or ICAS) specifications. It's probably not designed for that. You should be okay with any Ham use up to 20 Amps, then. The 150 mV refers to ac "noise" riding on the DC output. In a linear supply, it's almost always 120 Hz AC hum. In a switcher it is more likely noise from the switching circuits themselves that can include many different frequencies. The specifications don't say if it's 150 mV peak to peak or RMS, but many switchers show up to 150 mVpp in their outputs. That is usually a worst-case level, as far as I've seen. Depending upon what frequencies that noise contains, it may or may not pose a problem for us with Ham gear. That brings up the final issue: RF noise. Unlike linear supplies that use a big transformer, rectifier diodes and some sort of linear regulator (or no regulator at all), switcher supplies generate a lot of noise. That's because they "chop" the incoming voltage at a very high frequency. That high frequency allows the supply to use relatively lightweight and efficient transformers, but it also generates harmonics that extend up through the HF spectrum at least. That noise may be radiated from the box, radiated from the supply cord connected to the mains (and so by the mains lines themselves, or it may be passed into your rig via the DC supply line. The specifications for this supply say nothing about the amount of noise the supply generates. That's not a surprise. For most uses the RF noise is unimportant and it's one of the most difficult things for many who use these supplies to assess without actually trying the unit in the shack. There aren't all the definitive answers you'd like, I'm sure, but since I didn't see any other responses to your questions, it's what I can offer! 73, Ron AC7AC _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
